Yondó/El Totumo/manatí manatí información para monografía 1 · Yondó/El Totumo/manatí manatí información para monografía creado 29.3.99 modificado 9.8.06 ∑páginas 32

Yondó/El Totumo/manatí manatí información para monografía creado 29.3.99 modificado 9.8.06 ∑páginas 32 página 1

www.neotropicos.org Luis Carlos García Lozano <[email protected]>

Foto USFWS/Galen Rathbun

Foto © U.S. Fish and Wildlife ServiceFoto© Patrick M. Rose

Foto© Patrick M. Rose


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U.S. FISH AND WILDLIFE SERVICEDIVISION OF ENDANGERED

SPECIES

SPECIES ACCOUNTS

Source: Endangered and ThreatenedSpecies of the Southeastern United States

(The Red Book) FWS Region 4 --As of 8/93

WEST INDIAN MANATEETrichechus manatusFAMILY: Trichechidae STATUS: Endangered, Federal Register,March 11, 1967, June 2, 1970

DESCRIPTION: The West Indian Mana-tee is a large gray or brown aquaticmammal. Adults average about 10 feetlong and weigh 1,000 pounds. They haveno hindlimbs, and their forelimbs are mo-dified as flippers. Manatee tails are flatte-ned horizontally and rounded. Their bodyis covered with sparse hairs and theirmuzzles with stiff whiskers. Sexes aredistinguished by the position of the geni-tal openings and presence or absence ofmammary glands. Manatees will consu-me any aquatic vegetation available tothem and sometimes even shoreline vege-tation. Although primarily herbivorous,they will occasionally feed on fish. Ma-natees may spend about 5 hours a day fe-eding, and may consume 4 to 9 percent oftheir body weight a day.

REPRODUCTION AND DEVE-LOPMENT: Observations of matingherds indicate that females mate with anumber of males during their 2- to 4-week estrus period, and then they gothrough a pregnancy estimated to last 12

to 14 months (O'Shea 1992). Births occurduring all months of the year with aslight drop during winter months. Mana-tee cows usually bear a single calf, but1.5 percent of births are twins. Calvesreach sexual maturity at 3 to 6 years ofage. Mature females may give birth every2 to 5 years. The only long-term, stablebond between manatees is that between acow and her calf. Weaning generallyoccurs between 9 and 24 months of age,although a cow and calf may continue toassociate with each other for severalmore years. There is little information onthe life-time reproductive output of fema-les, although they may live over 50 years.

RANGE AND POPULATION LEVEL:During the winter months, the UnitedStates' manatee population confines itselfto the coastal waters of the southern halfof peninsular Florida and to springs andwarm water outfalls as far north assoutheast Georgia. Manatees also winterin the St. Johns River near Blue SpringState Park. During summer months, theymay migrate as far north as coastal Virgi-nia on the east coast and the Louisianacoast on the Gulf of Mexico.

Manatee populations also exist outsidethe continental United States in coastalareas of the Caribbean and Central andSouth America. In Puerto Rico, manateesapparently occur around the southern andeastern end of the island and around near-by Vieques Island. Except for rare sigh-tings, manatees seem to be absent fromthe Virgin Islands at present, but fossilshave been found in middens on St. Croix. The population of manatees in Floridahas been estimated to be at least 1,865 in-dividuals. There are an estimated 60 to100 manatees in Puerto Rico. In the last

decade, yearly mortality in Florida hasaveraged nearly 150 animals a year, dou-ble that of the preceding decade. Theaverage proportion of first-year calves inthe population is 10 percent with a rangeof 5 to 15 percent.

HABITAT: Manatees inhabit both saltand fresh water of sufficient depth (1.5meters to usually less than 6 meters)throughout their range. They may be en-countered in canals, rivers, estuarine ha-bitats, saltwater bays, and on occasionhave been observed as much as 3.7 milesoff the Florida Gulf coast. Between Octo-ber and April, Florida manatees concen-trate in areas of warmer water. When wa-ter temperatures drop below about 21 to22 degrees Centigrade, they migrate tosouth Florida or form large aggregationsin natural springs and industrial outfalls.Severe cold fronts have been known tokill manatees when the animals did nothave access to warmwater refuges. Du-ring warmer months they appear to choo-se areas based on an adequate foodsupply, water depth, and proximity tofresh water. Manatees may not need freshwater but they are frequently observeddrinking fresh water from hoses, sewageoutfalls, and culverts. There is no eviden-ce of any periodicity in manatee habitatuse in Puerto Rico.

CRITICAL HABITAT: The followingareas in Florida (exclusive of those exis-ting manmade structures or settlementswhich are not necessary to the normal ne-eds or survival of the species) are criticalhabitat for the manatee: Crystal Riverand its headwaters known as King's Bay,Citrus County; the Little Manatee Riverdownstream from the U.S. Highway 301bridge, Hillsborough County, the Little

Manatee River downstream from theLake Manatee Dam, Manatee County;the Myakka River downstream fromMyakka River State Park, Sarasota andCharlotte Counties; the Peace Riverdownstream from the Florida State High-way 760 bridge, DeSoto and CharlotteCounties; and Charlotte Harbor north ofthe Charlotte-Lee County line, CharlotteCounty; Caloosahatchee River downs-tream from the Florida State Highway 31bridge, Lee County; all United States te-rritorial waters adjoining the coast and is-lands of Lee County; all United States te-rritorial waters adjoining the coast and is-lands and all connected bays, estuaries,and rivers from Gordon's Pass near Na-ples, Collier County, southward to andincluding Whitewater Bay, MonroeCounty; all waters of Card, Barnes,Blackwater, Little Blackwater, Manatee,and Buttonwood Sounds between KeyLargo, Monroe County; and the mainlandof Dade County; Biscayne Bay, and alladjoining and connected lakes, rivers, ca-nals, waterways from the southern tip ofKey Biscayne northward to and includingMaule Lake, Dade County; all of LakeWorth, from its northernmost point im-mediately south of the intersection ofU.S. Highway 1 and Florida State High-way A1A southward to its southernmostpoint immediately north of the town ofBoynton Beach, Palm Beach County; theLoxahatchee River and its headwaters,Martin and West Palm Beach Counties;that section of the intracoastal waterwayfrom the town of Sewalls Point, MartinCounty, to Jupiter Inlet, Palm BeachCounty; the entire section of waterknown as the Indian River, from its nor-thernmost point immediately south of theintersection of U.S. Highway 1, and Flo-rida State Highway 3, Volusia County,



southward to its southernmost point nearthe town of Sewalls Point, MartinCounty; the entire inland section of waterknown as the Banana river and all water-ways between the Indian and Banana ri-vers, Brevard County; the St. Johns Riverincluding Lake George, and includingBlue Springs and Silver Glen Springsfrom their points of origin to their con-fluences with the St. Johns River; thatsection of the Intracoastal Waterwayfrom its confluence with the St. MarysRiver on the Georgia-Florida border tothe florida State Highway A1A bridgesouth of Coastal City, Nassau and DuvalCounties.

REASONS FOR CURRENT STATUS:The manatee population was probablymore abundant in the 18th or 19th cen-tury than today. Initial population decrea-ses probably resulted from overharves-ting for meat, oil, and leather. Today,hunting is prohibited and is not conside-red a problem, although there is an occa-sional incidence of poaching. Heavymortality does occur, however, from ac-cidental collisions with boats and barges,and from canal lock operations.

Manatee population trends are poorlyknown, but deaths have increased stea-dily (6.1 percent a year, exponential re-gression, 1976 to 1991). Mortalities fromcollisions with watercraft are up 10.3 per-cent a year from 21 percent of all deathsin 1976 to 1980 to 29 percent in 1986 to1991. Deaths of dependent calves are up12 percent a year from 14 to 24 percentof all deaths. The combination of highmortality rates and low reproductive rateshave led to serious doubts about the spe-cies' ability to survive in the United Sta-tes.

Another closely related factor in the de-cline has been the loss of suitable habitatthrough incompatible coastal deve-lopment, particularly destruction of sea-grass beds by boating facilities. In PuertoRico, the primary cause of manatee mor-tality seems to be from entanglement ingill nets. Collisions with boats and illegalkilling of manatees for food may also beaffecting the Puerto Rican population tosome extent, but supporting data are limi-ted.

MANAGEMENT AND PROTECTION:Based on revised recovery plan (1989)recommendations, the primary objectivein the recovery of the Florida populationof the West Indian manatee is to reesta-blish and maintain optimum sustainablepopulations in natural habitats throughoutthe manatee's historic range. To accom-plish this primary objective there are se-veral sub-objectives. They are:

1. Minimize human-caused injuries andmortalities to manatees. Rescue and reha-bilitate sick, injured, or orphaned mana-tees. Minimize mortality from boat andbarge collisions, water control structures,and poaching. Evaluate effectiveness ofcurrent and future regulations and enfor-cement efforts. Conduct programs to in-form and educate the public and developbilateral and multilateral agreements withother countries for manatee conservationand research.

2. Minimize alteration, degradation, anddestruction of habitat used by manateesand monitor its status. (Adverse habitatalteration may result from human use ofwater resources and industrial and resi-dential .development.) Evaluate potential

hazards such as coastal zone deve-lopment, outer continental shelf oil andgas development, toxicants, dredging, sil-tation, and power plant failures. Identify,protect, and monitor areas of special sig-nificance to manatees and enhance habi-tats used by manatees.

3. Minimize harassment of manateesfrom boat and barge traffic, fishing, di-ving, and swimming.

4. Determine and monitor status of mana-tee population and determine aspects oflife history and ecology.

5. Coordinate implementation of reco-very activities, monitor and evaluate pro-gress, and periodically update and reviserecovery plan.

A recovery plan developed specificallyfor the manatee population in PuertoRico indicates three primary objectivesfor recovery. The first objective is toidentify, assess, and reduce human-rela-ted mortality, especially that related togill net entanglement. The second objec-tive is to identify and minimize altera-tion, degradation, and destruction of ha-bitats important to the survival and reco-very of the Puerto Rico manatee popula-tion. The third objective is to develop thecriteria and biological information neces-sary to determine whether and/or when todelist or downlist (reclassify to threate-ned) the Puerto Rican population of ma-natees.

REFERENCES:

Hartman, D. S. 1979a. Ecology and beha-vior of the manatee (Trichechus manatus)in Florida. Am. Soc. of Mammal. Spec.Publ. 5. 153 pp.

Hartman, D. S. 1979b. West Indian Ma-natee. Pages 27-39 in J.N. Layane,Threatened. Rare and Endangered Biotaof Florida, Vol. 1, Mammals. UniversityPresses of Florida, Gainesville.

O'Shea, T. J., B. B. Ackerman, and H.F.Percival (eds.). 1992. Interim report ofthe technical workshop on manatee popu-lation biology. Manatee Population Re-search Report No. 10. Florida Cooperati-ve Fish and Wildlife Research Unit,Univ. of Florida, Gainesville, FL. 83 pp.

Powell, J. A. and G. B. Rathbun. 1984.Distribution and abundance of manateesalong the northern coast of the Gulf ofMexico. Northeast Gulf Science. Vol. 7.No. 1, p. 1-28.

**U. S. Fish and Wildlife Service. 1989.Florida Manatee Recovery Plan. U.S.Fish and Wildlife Service, Atlanta, Geor-gia. 98 pp.

**U. S. Fish and Wildlife Service. 1986.Recovery Plan for the Puerto Rico Popu-lation of the West Indian (Antillean) Ma-natee. U.S. Fish and Wildlife Service,Atlanta, Georgia. 35 pp.

For more information please contact:

U. S. Fish and Wildlife Service6620 Southpoint Drive SouthSuite 310Jacksonville, Florida 32216-0912

Telephone: (904)232-2580



http://bluegoose.arw.r9.fws.gov/NWRSFiles/WildlifeMgmt/Specie-sAccounts/Mammals/FLManatee/FLManateeTableOfContents.html

West Indian Manatee, Florida Population

The information provided in this docu-ment is from the Draft Florida ManateeRecovery Plan, second revision, preparedby the Florida Manatee Recovery Team.U.S. Fish and Wildlife Service, Atlanta,GA. 1993. 176 pp. Copies of the comple-te recovery plan may be purchased from:U.S. Fish and Wildlife Reference Service, 5430 Grosvenor Lane, Suite 110, Bethesda, Maryland 20814,(301) 492-6403or 1-800-582-3421.

Table of Contents

Introduction, Taxonomy and SpeciesDescription Population Biology

Population Structure Population Size

Population Demography, Distributionand Habitat Use Patterns Trophic Relationships and Reproduction Mortality, Contaminants and PollutionEffects Recovery Plan Accomplishments Literature Cited and Bibliography Additional Information

Brochure of Manatee Questions and Ans-wers.

http://refuges.fws.gov/NWRSFiles/WildlifeMgmt/SpeciesAccounts/Mammals/FLManatee/FLManateeTableOfContents.html -- Re-vised: 18 December 1996

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Manatee Recovery PlanIntroduction, Taxonomy andDescription

Introduction

The West Indian manatee (Trichechusmanatus) is one of the most endangeredmarine mammals in coastal waters of theUnited States. In the southeastern U.S.,manatees are limited primarily to Floridaand Georgia. This group constitutes a se-parate subspecies called the Florida ma-natee that appear to be divided into atleast two virtually separate populations --one centered along the Atlantic Coast andthe other on the Gulf of Mexico coast ofFlorida. Despite concerted research, ithas not been possible to develop a relia-ble estimate of manatee abundance inFlorida. The highest single-day count ofmanatees from an aerial survey is 1,856animals in January 1992 (Ackerman et al.1992).

Historical accounts and archeologicalevidence of manatees prior to the firsthalf of the 20th century are poor and of-ten contradictory (O'Shea 1988). It doesindicate that manatees probably are asgeographically widespread today as theywere historically. They were hunted bypre-Columbian indians, but the extent towhich they were taken is unclear. AfterSpanish occupation, Florida's humanpopulation increased and manatees pro-bably were taken in greater numbers.Commercial and subsistence hunting,particularly in the 1800s, probably redu-

ced the population significantly. In 1893,the State of Florida passed legislationprohibiting the killing of manatees. Ge-netic studies, however, indicate that thereduction did not cause a "genetic bottle-neck" (McClenaghan and O'Shea 1988).

The long-term survival of manatees inFlorida, however, is uncertain. Knownmortality, which averaged over 170 ani-mals per year between 1988 and 1992, ismore than twice what it was in the late1970s.

Given what is known about the presentpopulation size and the species' ability toproduce only a single calf every 2.5-5years per mature female, mortality maybe exceeding the populations' ability toproduce new animals. The major threatsto Florida manatees are collisions withwatercraft, which account for about 25percent of known manatee deaths in Flo-rida annually, and destruction anddegradation of habitat caused by wides-pread development throughout much ofthe species' Florida range.

Based on the known minimum size of thesoutheastern U.S. manatee populations,Florida manatees constitute the largestknown group of West Indian manateesanywhere in the species' range. Outsidethe United States, manatees occur in theGreater Antilles, on the east coast of Me-xico and Central America, along thenorth and northeastern coast of SouthAmerica, and in Trinidad and Tobago. Inthese areas, remaining populations arebelieved to be much smaller than the U.S.population and are subject to poachingfor food, incidental take in gillnets, andhabitat loss. Manatee protection pro-grams in other countries are not well or-ganized or supported and, in this context,

protection of the Florida population takeson international significance.

Taxonomy

The West Indian manatee, Trichechusmanatus Linnaeus, 1758, is one of fourliving species of the mammalian OrderSirenia. The other three sirenians are theWest African manatee (T. senegalensis),the Amazonian manatee (T. inunguis),and the dugong (Dugong dugon). Allfour species are aquatic herbivores listedas endangered or threatened under theU.S. Endangered Species Act. A fifthspecies, Steller's sea cow (Hydrodamalisgigas), existed in sub-arctic waters of theBering Sea. Hunted to extinction within27 years of its discovery in 1741, Steller'ssea cow was an 8 m (26 ft) long toothlesssirenian that fed on kelp (Reynolds andOdell 1991).

Two subspecies of West Indian manateeare now recognized: the Florida manatee,T. manatus latirostris, which occurs inthe southeastern U.S., and the Antilleanmanatee, T. manatus manatus foundthroughout the remainder of the species'range. The Florida manatee was first des-cribed by Harlan (1824) as a separatespecies, Manatus latirostris. Later, Hatt(1934) recognized Florida manatees as asubspecies of T. manatus Linnaeus. Al-though later researchers (Moore 1951 andLowery 1974) questioned the validity ofthe subspecies status, Domning andHayek (1986) carefully examined mor-phological characteristics and concludedthat the distinction was warranted.

The ranges of the two subspecies mayoverlap on the coast of Texas; however,there is no confirming evidence. Swiftcurrents and open water in the Florida



Strait appear to be effective barriers pre-venting the movement of manatees bet-ween the Greater Antilles and Florida(Domning and Hayek 1986).

Species Description

West Indian manatees are massive fusi-form-shaped animals with skin that isuniformly dark grey, wrinkled, sparselyhaired, and rubber-like. Manatees possesspaddle-like forelimbs, no hind limbs, anda spatulate, horizontally flattened tail.Their bones are massive and heavy withno marrow cavities in the ribs or long bo-nes of the forearms (Odell 1982). Adultsaverage about 3.5 m (11.5 ft) in lengthand 1000 kg (2,200 lbs) in weight, butmay reach lengths of up to 4.6 m (15 ft.)(Gunter 1941) and 1,650 kg (3,630 lbs)(Rathbun et al. 1990). Newborns average1.2 to 1.4 m (4-4.5 ft) in length and about30 kg (66 lbs) (Odell 1981).

The nostrils, located on the upper snout,open and close by means of muscularvalves as the animals surface and dive(Hartman 1969 and Husar 1977). A mus-cular, flexible upper lip is used with theforelimbs to manipulate food into themouth (Odell 1982). Bristles are locatedon the upper and lower lip pads. Molarsdesigned to crush vegetation form conti-nuously at the back of the jaw and moveforward as older ones wear down. Theeyes are very small, close with sphincteraction, and are equipped with inner mem-branes that can be drawn across the eye-ball for protection. Externally, the earsare minute with no pinnae. Internally, theear structure suggests that they can hearlow frequency sound within a relativelynarrow low frequency range, that theirhearing is not acute, and that they havedifficulty in localizing sound (Ketten et

al. 1992). Manatees have two axillarymammae, one at the base of each fore-limb.

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Manatee Recovery Plan Popula-tion Biology, Structure and Size

Population Biology

Recent information on manatee[1] popu-lation biology was reviewed during a te-chnical workshop sponsored by the Fishand Wildlife Service and the former Flo-rida Department of Natural Resources[2]and held on 4-6 February 1992 (O'Sheaet al. 1992). The objectives of theworkshop were to synthesize existing in-formation, evaluate the strengths andweaknesses of current data sets and re-search methods, and make recommenda-tions for future research, particularlyconstructing new population models.

There has been a tremendous increase inreproductive and mortality data since thelast such workshop in 1978. There havebeen recent breakthroughs in age deter-mination and survival rate estimation,which were reported at the workshop.The value of maintaining a long-term in-dividual animal photoidentification data-base was emphasized. This database notonly provides information on manatee re-productive traits and movements, it pro-vides capture-recapture histories that canbe used in a variety of statistical modelsto determine aspects of manatee popula-tion dynamics. It was concluded thatsufficient data now exist to allow deve-lopment of new population models. The

Population Model Working Group em-phasized that there will not be one finaland conclusive model; rather modellingwill be an ongoing process that evolvesas databases and modelling tools are im-proved.

Population Structure

Three principal lines of research havebeen particularly helpful in identifyingpopulation structure of manatees in Flori-da. These are analyses of the manateephotoidentification scar catalogue, tele-metry, and genetic studies. Informationfrom these sources suggests that there islittle routine intermixing of individualmanatees living on the east and westcoasts of Florida, but that, genetically,they constitute a single population.

As of the end of 1991, the manatee scarcatalogue maintained by the Fish andWildlife Service since 1981 includedover 913 distinctively scarred manateesrepresented by 9,796 sightings or resigh-tings from throughout the SoutheasternU.S. (Beck and Reid 1992). Within thisextensive data set, no individuals havebeen documented from both the Atlanticand Gulf of Mexico coasts. (One animalhas been documented occurring on theAtlantic coast and on the west side ofLake Okeechobee.) In addition, radio-tracking studies of over 100 manatees bythe Service and the former Florida De-partment of Natural Resources havefound no movement of animals betweenFlorida's east and west coasts. Notwiths-tanding these findings, there appears tobe at least some genetic exchange aroundor across the peninsula based on geneticresearch. A study of tissues from 59 ma-natees collected from throughout Florida

found little genic variability among geo-graphic regions (McClenaghan andO'Shea 1988). It seems likely, therefore,that there is occasional movement ofsome animals between the two coasts thathas yet to be documented, that some in-terbreeding occurs at the southern tip ofFlorida or in Lake Okeechobee, or thatthese events occurred very recently.

Within both the east and west coast ma-natee populations, documented move-ments suggest that at least some looselyformed subpopulations or groups existwhich may constitute useful managementunits. These groups tend to return to thesame warm-water refuge(s) each winterand have similar non-winter distributionpatterns. For example, on the east coast, acore group of more than 70 manatees usethe Blue Spring warm water refuge onthe upper St. Johns River. Radio-trackingstudies (Bengtson 1981) and other infor-mation (Beeler and O'Shea 1988 and Ma-rine Mammal Commission 1988) suggestthat most "Blue Spring manatees" tend toremain in the upper St. Johns River. Onthe west coast, Rathbun et al. (1990) re-port that of 100 recognizable manateesidentified at the Kings Bay and Homo-sassa River warm water refuges innorthwest Florida in the early 1980s, 92% of the females and 84 % of the malesreturned to the same refuge each year.Radio-tracking work suggests that manyanimals wintering at Crystal River dis-persed north in warm seasons to riversalong the Big Bend Coast, particularlythe Suwannee River, and some movesouth to Tampa Bay and beyond.

The existence of more or less distinctsubgroups in the southern half of Florida(i.e., south of Cape Canaveral on the east



coast and Tampa Bay on the west coast)is debatable. It is possible that manateesusing warm water refuges in Tampa Bay,the Caloosahatchee River, and CollierCounty may be somewhat discretegroups; however, given available data,possible sampling biases in studies todate, the proximity of these areas to oneanother, and the distribution of manateesthroughout this stretch of coast, such dis-tinctions are highly speculative at thistime.

Population Size

Despite considerable effort in the early1980s, scientists have been unable to de-velop a useful means of estimating ormonitoring trends in the size of the ove-rall manatee populations in the southeastUnited States (O'Shea 1988 and O'Sheaet al. 1992). Even though many manateesaggregate at warm water refuges in win-ter and most if not all such refuges areknown, direct counting methods (i.e., byaerial and ground surveys) have beenunable to account for uncertainty in thenumber of animals that may be awayfrom these refuges at any given time, thenumber of animals which are not seenbecause of turbid water, and other fac-tors. The use of mark-resighting techni-ques to estimate manatee population sizebased on known animals in the manateephotoidentification database also hasbeen impractical because of the difficultyin estimating the proportion of knownanimals in the population. Sampling pro-tocols to estimate population size usingthese techniques would require majorchanges in the data collection methodsand survey effort far beyond those possi-ble based on available resources.

The only credible data on population size

have been minimum point estimates ba-sed on maximum counts of animals at allwinter refuges made within one or twodays of each other. Based on such infor-mation in the late 1980s, the total numberof manatees throughout Florida wasknown to be at least 1,200 animals(Reynolds and Wilcox 1987). Becauseaerial and ground counts at winter refu-ges are highly variable depending on theweather, water clarity, manatee behavior,and other factors (Packard et al. 1985) in-terpretation of analyses for temporaltrends is difficult (Packard and Mulho-lland 1983 and Garrott et al. 1992). Ae-rial survey methods useful for monitoringtrends in manatee abundance have yet tobe developed.

Beginning in 1991, the former FloridaDepartment of Natural Resources initia-ted a synoptic aerial survey program tocount manatees in potential winter habitatduring periods of severe cold weather(Ackerman 1992). During a survey in Ja-nuary 1991, 1,268 manatees were coun-ted (697 east coast and 589 west coast).In February 1991, 1,465 manatees werecounted (813 east coast, 652 west coast).In 1992, one survey was done in Januaryyielding a count of 1,856 animals (907east coast, 949 west coast. No synopticsurveys were done during the winter of1992-93 because of the lack of severemid-winter cold fronts. It remains un-known what proportions of the manateepopulations were counted in these sur-veys. The counts do not provide a basisfor assessing population trends. Based onthe surveys, the sizes of the east and westcoast populations appear to be approxi-mately equal and the total number of Flo-rida manatees is at least 1,856 animals.

On a more limited basis, it has been pos-sible to estimate and monitor the numberof manatees using the Blue Spring andCrystal River warm water refuges. AtBlue Spring, with its unique combinationof clear water and confined spring area, ithas been possible to count the number ofresident animals by identifying individualmanatees from scar patterns. The data in-dicate that this group of animals has in-creased steadily since the early 1970swhen it was first studied. During the1970s the number of manatees using thespring increased from 11 to 25 (Bengtson1981). In the mid-1980s about 50 ani-mals used the spring (Beeler and O'Shea1988), and in the winter of 1992-1993,the number increased to 73 animals(Wayne Hartley, personal communica-tion).

On the west coast of Florida, the clear,shallow waters of Kings Bay have madeit possible to monitor the number of ma-natees using the warm-water refuge inKings Bay at the head of the Crystal Ri-ver. Large aggregations of manateesapparently did not exist there until recenttimes (Beeler and O'Shea 1988). The firstcareful counts were made in the late1960s. Since then manatee numbers haveincreased significantly. In 1967-1968Hartman (1979) counted 38 animals. By1981-1982, the maximum winter counthad increased to 114 animals (Powell andRathbun 1984) and in 1992, the maxi-mum count was 292 animals (U.S. Fishand Wildlife Service, unpublished data).Both births and immigration of animalsfrom other areas have contributed to theincreases at Crystal River and BlueSpring.

The trends at Blue Spring and Crystal Ri-

ver are not believed to be reflective ofmanatee population trends elsewhere inFlorida (O'Shea and Langtimm 1992). Inpart, this is because the observed increa-ses at these sites are due to immigrationof animals, because mortality differs indifferent parts of Florida, and becausemaximum aerial survey counts at otherwinter refuges in Florida from 1977and 1992 (Reynolds 1992) show no com-parable increases. Based on preliminaryanalyses of survivorship, populationgrowth at Blue Spring and Crystal Riverappears reasonable, while increases alongthe Atlantic coast do not seem likely(O'Shea and Langtimm 1992).

Footnotes

1 The unmodified word "manatees" he-reafter refers to Florida manatees, Triche-chus manatus latirostris.

2 In July 1993 most offices and functionsof Florida's Department of Natural Re-sources were combined with the officesand functions of the State's Departmentof Environmental Regulation to createthe Department of Environmental Protec-tion.

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Manatee Recovery Plan Popula-tion Demography and Distribu-tion

Population Demography

The east and west coast populations arebelieved to be approximately equal in



size. The sex ratio of adults and calves atCrystal River is 1:1 (Rathbun et al. 1992)and is considered reflective of the popu-lations' overall sex ratio.

An evaluation of manatee reproductionbased on carcasses recovered from bothcoasts of Florida between 1976 and 1992found that manatees may mature as earlyas 3-4 years of age; 46 % of the femaleswere sexually mature; and 33 % of themature females were pregnant (Marmon-tel 1993). The annual pregnancy rate wasestimated to be about 21 % and the grossannual recruitment rate was estimated tobe 7% (Marmontel 1992). These repro-ductive rates and survivorship data deri-ved from ages-at-death indicate a stableor slightly increasing population withhigh probability of persistence over thelong term provided present conditions re-main constant. Sensitivity analyses showthat high adult survival is critical for po-pulation maintenance, whereas calf mor-tality has little effect on populationgrowth rate and persistence probability(Marmontel 1992).

Preliminary analyses of survival rates ba-sed on resighting data in the manatee scarcatalogue suggest that mean annual adultsurvival differs on the east and westcoasts. Survival rates were highest atCrystal River, slightly lower at BlueSpring, and lowest on the Atlantic coast.Based on available population models,these rates may be high enough to permitpopulation growth at Crystal River andBlue Spring, but are too low for growthon the Atlantic coast given apparent ratesof reproduction and mortality and survi-val rates in immature age classes. Furtherrefinements to the database and analytictechniques are needed, however, to more

accurately estimate and compare survivalrates in these three areas.

Some information on the proportion ofcalves in the population is available fromcounts of cow-calf pairs during aerialsurveys. From winter surveys of majorrefuges at power plant outfalls between1977 and 1992, annual percentages ofcalves observed range from 12.8-6.6 %,with maximum one-day calf counts inthose years ranging from 23 to 73 ani-mals (Reynolds 1992). The overall per-cent and maximum number of calvessighted in this data set show a decline inrecent years suggesting a decline in re-cruitment of calves into older age classes.While this trend, combined with informa-tion on increasing perinatal mortality (seemortality below), is a cause for concern,some problems exist in interpreting aerialcalf counts (Rathbun 1990). Estimatedcalf percentages from recent state-widesurveys are 8.6 % in January 1991, 8.8 %in February 1991 survey, and 8.6 % inJanuary 1992 (Ackerman 1992 andAckerman personal communication). Theactual numbers of calves counted in theFebruary 1991 and January 1992 surveyswere 129 and 139 calves, respectively(Ackerman personal communication).The latter count, however, excludes cal-ves in 13 percent of the count (248 of1865 animals) where observers did notdistinguish calves from adults due tosighting conditions.

Distribution and Habitat UsePatterns

Due to telemetry, aerial surveys, photoi-dentification sighting records, and otherstudies over the past 15 years, manateedistribution in the Southeastern U.S. is

now well known (Beeler and O'Shea1988, O'Shea 1988, Marine MammalCommission 1988, and Lefebvre et al.1989). In general, the data show that ma-natees exhibit both opportunism and in-dependence in their distribution and mo-

vement. They are able to un-dertake extensive north-south migrations with seaso-nal distribution determinedby water temperature.

When ambient water tempe-ratures drop below 20 de-grees C (68 degrees F) in au-tumn and winter, manateesaggregate within the confi-nes of natural or artificialwarm water refuges (Lefeb-vre et al. 1989) or move tothe southern tip of Florida(Snow 1991). Most artificialrefuges are created by warmwater outfalls from powerplants or paper mills. Thelargest winter aggregations(50 or more animals) are atrefuges in central andsouthern Florida (Table 1),although three or four sma-ller aggregations (about 15or fewer animals) use warmwater outfalls in northernFlorida and southern Geor-gia on the east coast (MarineMammal Commission1988). The northernmost re-fuge used regularly on thewest coast is at Crystal Ri-ver. Most manatees return tothe same warm water refu-ges each year; however,some use different refuges indifferent years and others

use two or more refuges in the same win-ter (Reid and Rathbun 1984 and 1985,Rathbun et al. 1990, and Reid et al.1991). There are also many lesser known,minor aggregation sites used as tempo-rary thermal refuges. Most of these are

Manatee Recovery Plan/Table 1 Aggregation Sites

List of major aggregation sites for Florida Manatees (* = ma-jor sites with 25 or more manatees in aggregations).

East Coast:

1.Georgia Pacific (Glynn County, GA) 2.Gilman Paper Company (Camden County, GA) 3.Container Corporation of America (Nassau County, FL) 4.Jefferson Smurfit Corporation (Duval County, FL) 5.JEA Kennedy Generating Station (Duval County, FL) 6.JEA Southside Generating Station (Duval County, FL) 7.Blue Springs (Volusia County, FL)* 8.OUC Indian River Power Plant (Brevard County, FL)* 9.FPL Canaveral Power Plant (Brevard County, FL)* 10.Vero Beach Power Plant (Indian River County, FL) 11.Henry D. King Electric Station (St. Lucie County, FL) 12.FPL Riviera Beach Power Plant (Palm Beach County, FL)* 13.FPL Port Everglades Power Plant (Broward County, FL)* 14.FPL Fort Lauderdale Power Plant (Broward County, FL)* 15.Sebastian River (Brevard County, FL)*

West Coast:

1.FPC Crystal River Power Plant (Citrus County) 2.Crystal River (Citrus County)* 3.Homosassa River (Citrus County)* 4.TECO Port Sutton Power Plant (Hillsborough County) 5.TECO Big Bend Power Plant (Hillsborough County)* 6.FPC Bartow Power Plant (Pinellas County)* 7.FPL Fort Myers Power Plant (Lee County)* 8.Port of the Islands (Collier County)* 9.Myakka River (Sarasota County)*

Abbreviations: FPC Florida Power Corporation FPL Florida Power and Light Company JEA Jacksonville Electric Authority OUC Orlando Utilities Commission TECO Tampa Electric Company



canals or boat basins where warmer wa-ter temperatures persist as temperaturesin adjacent bays and rivers decline.

During mild winter periods, manateesmove to nearby grassbeds to feed. Forexample, manatees using the RivieraPower Plant feed in adjacent Lake Worthand in Jupiter and Hobe sounds 12-15miles to the north (Packard 1981); ani-mals using the Port Everglades powerplant feed in grass beds in Biscayne Bay15-20 miles to the south (MarineMammal Commission 1988); animals inKings Bay feed on submerged vegetationnear the mouth of the Crystal River(Rathbun et al. 1990); animals at BlueSpring leave the spring run to feed onfreshwater aquatic plants along the St.Johns River and associated waters nearthe Spring (Bengston 1981); and animalsusing outfalls from a paper plant insouthern Georgia and a container manu-facturing plant on Amelia Island in nor-thern Florida fed in creeks within one totwo miles of those refuges (Zoodsma1991).

As water temperatures rise in spring, ma-natees disperse from winter aggregationareas. While some remain near their win-ter refuges, others undertake extensivetravels along the coast and far up riversand canals. On the east coast, summersightings drop off rapidly north of Geor-gia (Lefebvre et al. 1988) and are rarenorth of Cape Hatteras (Rathbun et al.1982); the northernmost sighting is fromthe Potomac River, Maryland. On thewest coast, sightings drop off sharplynorth of the Suwannee River in Florida(Marine Mammal Commission 1986), al-though a small number of animals --about

12-15 manatees -- are seen each summerin the Wakulla River at the base of theFlorida panhandle. Louisiana is conside-red the western limit of the Florida mana-tee's range (Powell and Rathbun 1984and Lefebvre et al. 1989); manatees inTexas are believed to be migrants fromMexico though this has not been confir-med (Domning and Hayek, 1986). Raresightings also have been made in the DryTortugas (Reynolds and Ferguson 1984)and the Bahamas (Odell et al. 1978).

In recent years, the most important springhabitat for the east coast population hasbeen the northern Banana River in Bre-vard County; more than 300 manateeshave been counted in this area shortly be-fore dispersing in late spring (Provanchaand Provancha 1988). A comparablespring aggregation area does not appearto exist on the west coast, although Char-lotte Harbor was visited in the spring byalmost half of the 35 manatees radio-tagged at the Fort Myers power plant inLee County (Lefebvre and Frohlich1986). During summer, manatees may befound almost anywhere in Florida wherewater depths are greater than 1-2 m(O'Shea 1988). They usually occur aloneor in pairs, although interacting groups offive to ten animals are not unusual.

Shallow grass beds with ready access todeep channels are preferred feedingareas. Manatees often use secluded ca-nals, creeks, embayments, and lagoons,particularly near the mouths of coastal ri-vers and sloughs, for feeding, resting, ca-vorting, mating, and calving (MarineMammal Commission 1986 and 1988).In estuarine and brackish areas, naturaland artificial fresh water sources aresought by manatees. As in winter, mana-

tees often use the same summer habitatsyear after year (Reid et al. 1991).

http://bluegoose.arw.r9.fws.gov/NWRSFiles/WildlifeMgmt/Specie-sAccounts/Mammals/FLManatee/FLManateeTrophic.html

Manatee Recovery Plan TrophicRelationships and Reproduction

Trophic Relationships

Manatees are herbivores that feed oppor-tunistically on a wide variety of submer-ged, floating, and emergent vegetation(see Table 2). They include submergedrooted seagrasses, emergent vascularplants, benthic algae, and floating plants.Manatees also forage opportunisticallyon detritus as illustrated by their use ofacorns in the upper St. Johns River(Bengtson 1981 and O'Shea 1986).

Feeding rates and food preferences de-pend, in part, on the season and availableplant species. Bengtson (1981 and 1983)reports that time manatees spent feedingin the upper St. Johns River was greatest(6-7 hrs/day) immediately before winter(August-November), least (3-4 hrs perday) in spring and summer (April-July),and intermediate (about 5 hrs/day) inwinter (January-March). He estimates an-nual mean consumption rates at 33.2 kg/day/manatee or about 4-9% of their bodyweight per day depending on season(Bengtson 1983). At Crystal River, Ethe-ridge et al. (1985) report cumulative dailywinter feeding times from 0 to 6 hrs. 10min. based on observations of three ra-dio-tagged animals over seven 24 hourperiods. The estimated daily consump-tion rates by adults, juveniles, and calveseating Hydrilla are 7.1, 9.6, and 15.7 per-

cent of body weight per day, respecti-vely.

Packard (1984) notes two feedingmethods in coastal seagrass beds: roo-ting, where virtually the entire plant isconsumed, and grazing, where exposedgrass blades are eaten without disturbingthe roots or sediment. In the winter of

Manatee Recovery Plan/Table 2 - Foods

Plants species commonly eaten by manatees (Hman 1979, Bengtson 1981, Packard 1981, Lefeand Powell 1990, and Zoodsma 1991).

Submerged Seagrasses -- Estuarine and Marin

Shoalgrass - Halodule wrightii Manatee grass - Syringodium filiforme Turtle grass - Thalassia testudinum Widgeongrass - Ruppia maritima Star grass - Halophila spp.

Submerged Plants -- Fresh Water Areas

Hydrilla - Hydrilla verticillata Wildcelery/eelgrass - Vallisneria americana Southern naiad - Najas quadalupensis Coontail - Ceratophyllum demersum Para grass - Panicum purpurascens Parrot's feather - Myriophyllum sp. Sago pondweed - Potamogeton pectinatus

Benthic Macroalgae -- Estuarine and Marine A

sea lettuce - Ulva sp. red algae - Gracilaria sp. caulerpa - Caulerpa prolifera

Floating Plants -- Fresh Water Areas

Water hyacinth - Eichhornia crassipes Pickerelweed - Pontederia lanceolata Water lettuce - Pistia stratiotes



1980-1981 in Lake Worth and JupiterSound on Florida's east coast, Packard(1981) reports that rooting was the predo-minant feeding mode with feeding scarsleft in beds of manatee grass having only4-7 % of the biomass found in adjacentundisturbed areas. She estimates 40 % ofthe grass beds near the Riviera PowerPlant warm water refuge were disturbedthat winter and suggests that the creationof bare patches favors the growth of ma-natee grass and shoalgrass which recolo-nize disturbed areas more rapidly thanturtle grass (Packard 1984). During themilder winter of 1988-89, Lefebvre andPowell (1990) found that manatees inHobe Sound appeared to prefer shoal-grass, that 46-67 % of the root biomasswas removed in feeding scars, and thatthe area disturbed by manatees was muchless than during the winter of 1980-81.

In the upper Banana River, Provanchaand Hall (1991) found spring concentra-tions of manatees grazing in grass bedsdominated by manatee grass. They alsoreported an apparent preference for ma-natee grass and shoalgrass over the ma-croalga Caulerpa spp. Along the Florida-Georgia border, Zoodsma (1991) foundthat manatees fed in salt marshes onsmooth cordgrass by timing feeding withperiods of high tide.

Reproduction

Breeding takes place when one or moremales (groups of up to 17 have been re-ported) are attracted to an estrus femaleto form an ephemeral mating herd (Mar-montel et al. 1992). Such herds mayremain together from a few hours to afew weeks. Permanent bonds betweenmales and females do not form. During

peak activity, the males in mating herdscompete intensely for access to the fema-le (Hartman 1979). Successive copula-tions involving different males arecommon. Some observations suggest thatlarger, presumably older, males dominateaccess to females early in the formationof mating herds and are responsible formost pregnancies (Rathbun et al. 1992).Females remain in estrus for about twoweeks (Lynn Lefebvre, personal commu-nication). Although breeding has been re-ported in all seasons, Hernandez et al.(1992) report that histological studies ofreproductive organs from salvaged malesfound evidence of sperm production in94 % of adult males recovered fromMarch through November, but only 20 %of adult males recovered from Decemberthrough February.

Females appear to reach sexual maturityat about age five (Marmontel 1992, Odellet al. 1992, Rathbun et al. 1992) and ma-les may reach sexual maturity at three tofour years of age (Hernandez et al. 1992).Manatees may live in excess of 50 years(Marmontel 1992) and may not undergoreproductive senescence (Marmontel etal. 1992); a captive animal named Julietgave birth to a calf in 1990 at which timeshe was estimated to be 43 to 48 years ofage (Bossart, personal communication).The length of the gestation period is un-certain but is thought to be between 12and 14 months (Odell et al. 1992,Rathbun et al. 1992, and Reid et al.1992). The normal litter size is one, withtwins reported rarely (Odell et al. 1992and Rathbun et al. 1992).

Calf dependency usually lasts one to twoyears after birth (Hartman 1979, Rathbunet al. 1992, and Reid et al. 1992). Calving

intervals vary greatly among individuals.They are probably not often less thanabout 2 to 2.5 years, but may be conside-rably longer depending on age andperhaps other factors (Marmontel 1992,Odell et al. 1992, Rathbun et al. 1992,and Reid et al. 1992). Females that abortor lose a calf due to perinatal death maybecome pregnant again within a fewmonths (Odell et al. 1992), or even weeks(Hartman 1979).

http://bluegoose.arw.r9.fws.gov/NWRSFiles/WildlifeMgmt/Specie-sAccounts/Mammals/FLManatee/FLManateeMortality.html

Manatee Recovery Plan Morta-lity, Contaminants and Pollution

Mortality

Data on manatee mortality in theSoutheastern U.S. have been collectedsince 1974 (Table 3, see recovery plan).It indicates a clear increase in manateedeaths over the last 15 years (6.1 %/yearexponential regression between 1976 and1991; Ackerman et al. 1992). Althoughboth natural and human-related causesare significant components of manateemortality, most of the increase in morta-lity can be attributed to increases in wa-tercraft-related deaths and perinataldeaths (Marine Mammal Commission1993).

A prominent cause of natural mortality insome years is cold stress. For example,following a severe winter cold spell at theend of 1989, 46 manatee carcasses whosedeath was attributed to cold stress wererecovered. Exposure to cold also is belie-ved to have caused many deaths in thewinters of 1977, 1981, and 1984 (O'Shea

et al. 1985). In 1982, a large number ofmanatees also died coincident with a redtide outbreak between February andMarch in Lee County, Florida (O'Shea etal. 1991). At least 37 manatees appear tohave died due to ingestion of filter-fe-eding tunicates which had accumulatedthe neurotoxin-producing dinoflagellatesresponsible for causing the red tide.Other natural causes of death are disease,parasitism, and non-human related inju-ries (O'Shea et al. 1985 and Ackerman etal. 1992). Some, and perhaps many peri-natal deaths are certainly due to naturalcauses; however, pollution, watercraft in-juries or disturbance, or other human-re-lated factors affecting pregnant andnursing mothers also may be responsiblefor a significant number of perinataldeaths.

The largest known human-related causeof manatee mortality is collisions withhulls and/or propellers of boats and ships.Between 1976 and 1991, watercraft-rela-ted deaths increased at an average of 10.3% per year, increasing from 21 % of alldeaths between 1976-1980 to 29 % bet-ween 1986-1991 (Ackerman et al. 1992).In 1992, the number of watercraft-relateddeaths declined by the largest amount inover 10 years (from 53 in 1991 to 38 in1992) although, given a decline in totaldeaths in 1992, it still represented 23 %of the total 1992 mortality. The next lar-gest human-related cause of manateemortality is entrapment in flood gates andnavigation locks. Such deaths declinedfrom an average of 8 animals per yearbetween 1978 and 1980 to an average of4 animals per year between 1989 and1990. In 1991 and 1992, however, theyincreased to 9 and 5, respectively.



Other known causes of human-relatedmanatee mortality include poaching andvandalism, entrapment in shrimp nets andother fishing gear, entrapment in waterpipes, and ingestion of marine debris. To-gether, deaths attributable to these causeshave remained constant and have been alow percentage of total known mortality,i.e., about 5 % between 1976-1980, 3 %between 1981-1985, and 2 % between1986 and 1991. In recent years, en-trapment in shrimp nets has been the lar-gest component of this catch-all categoryaccounting for possibly 8 of 26 deathsbetween 1986 and 1991.

Contaminants and PollutionEffects

The reliance of manatees on inshore ha-bitats and their attraction to industrial andmunicipal outfalls expose them to relati-vely high levels of contaminants. Despitethis relationship, there have been few stu-dies of contaminant levels and effects onmanatees. What information is availablesuggests that direct effects are not signifi-cant at a population level. O'Shea et al.(1984) investigated levels of pesticides,polychlorinated biphenyls, mercury, lead,cadmium, copper, iron, and selenium inmanatee tissues. Of these, only copper le-vels in the liver were found to be notablyhigh. The highest copper levels (1,200ppm dry weight) were found in animalsfrom areas of high herbicidal copper usa-ge and exceeded all previously reportedconcentrations in livers of wildmammals. Despite these findings, therewere no field reports of copper poisoningand no evidence of deleterious effects toindividual animals.

Manatees ingest various debris incidental

to feeding. Beck and Barros (1991) foundmonofilament fishing line, plastic bags,string, rope, fish hooks, wire, rubberbands, and other debris in the stomachsof 14.4 % of 439 manatees recovered bet-ween 1978 and 1986. Monofilament linewas the most common item found. Inmost cases, ingested items do not appearto affect animals. A few deaths, however,have been caused by ingesting wire,which perforated the stomach lining, andplastic sheeting, which blocked the diges-tive tract (Laist 1987). Discarded monofi-lament line and rope also have beenfound wrapped around flippers, some-ti-mes leading to serious injury or death(Beck and Barros 1991).

http://bluegoose.arw.r9.fws.gov/NWRSFiles/WildlifeMgmt/Specie-sAccounts/Mammals/FLManatee/FLManateeAccomplishments.html

Manatee Recovery Plan Accom-plishments

Under the guidance of previous ManateeRecovery Plans, Federal agencies, Stateagencies, and private organizations haveinitiated cooperative actions to addressimportant conservation needs upon whichthis plan builds. Some of the major initia-tives are reviewed below.

Watercraft Injuries and Deaths

The largest source of human-related ma-natee mortality is collisions with water-craft. Many, if not most, living manateesalso bear scars or wounds from vesselstrikes. A recent analysis of injuries to406 manatees killed by watercraft and re-covered between 1979 and 1991 foundthat 39 % were killed by propeller cuts,55 % were killed by impact, and 4 % had

both types of injuries, either of whichcould have been fatal (Wright et al.1992). Analyses of wounds suggest thatmost lethal propeller wounds were cau-sed by medium-sized or larger vessels,but that impact injuries appear to be cau-sed by fast-moving small- to medium-si-zed boats (Wright et al. 1992). Most pro-peller wounds are on the backs and sidesrather than the heads of animals, sugges-ting that they were diving to avoid colli-sion when hit. Because watercraft opera-tors cannot reliably detect and avoid hi-tting manatees, Federal and state mana-gers have sought to limit watercraft speedin areas where manatees are most likelyto occur to afford manatees time to avoidoncoming boats.

In 1989, the Florida Governor and Cabi-net approved a series of recommenda-tions by the former Florida Departmentof Natural Resources to improve protec-tion of manatees in 13 key manatee coun-ties (Brevard, Duval, Broward, Dade, In-dian River, Martin, Palm Beach, St. Lu-cie, and Volusia Counties on the eastcoast and Lee, Citrus, Collier, and Sara-sota on the west coast). Initial work hasbeen devoted to developing waterwayspeed and access (i.e., no entry) rules inthese counties. At this time, the FloridaGovernor and Cabinet have approvedcounty rules for eleven key counties.Efforts are underway to finalize rules forthe remaining two counties. Speed andaccess rules for boats also have been de-veloped by the Fish and Wildlife Serviceto protect manatees in certain NationalWildlife Refuges.

As initial work in the 13 key counties iscompleted, attention is shifting to deve-lopment and approval of county manatee

protection plans, and similar protectionof important manatee habitat in countiesnot listed among the 13 key counties willneed to be considered. Ongoing needs in-clude boater education, maintenance ofsigns and buoys, enforcement, complian-ce assessment, and periodic reevaluationof the effectiveness of the rules. Suchwork requires close cooperation betweenthe Office of Protected Species Manage-ment in the new Florida Department ofEnvironmental Protection, county offi-cials, the Florida Marine Patrol, the Flori-da Governor and Cabinet, the Fish andWildlife Service, and, of course, boaters.

Flood Gate and Navigation LockDeaths

Entrapment in flood gates and navigationlocks is the second largest cause of hu-man-related manatee deaths. In some ca-ses, manatees appear to have beencrushed in closing doors; in others, theymay have been pinned against narrowdoor openings by water currents rushingthrough openings and drowned. Mostflood gates implicated in manatee deathsare in Dade and Broward counties andare operated by the South Florida WaterManagement District. Most navigationlocks implicated in manatee deaths havebeen along waterway access routes toLake Okeechobee and are operated bythe Corps of Engineers. In the late 1970s,one quarter of all manatee deaths in DadeCounty were attributed to flood controlstructures.

In the early 1980s, steps were taken tomodify gate opening procedures to ensu-re openings were wide enough to allow amanatee to pass through unharmed. Stepswere also initiated to fence off openings



and cavities in gate structures in whichmanatees might become trapped. Mana-tee deaths subsequently declined and re-mained low for much of the 1980s (seeTable 3 in recovery plan). However, a re-cent increase in deaths at modified gatessuggests that the measure may only par-tially address the problem. A task forcewith representatives of the South FloridaWater Management District, the Corps ofEngineers, the new Florida Departmentof Environmental Protection, the DadeCounty Environmental Resource Mana-gement office, and the Fish and WildlifeService has been formed to examine fur-ther actions. Options being considered in-clude further modifications to gate ope-ning and closing sequences, sonar devi-ces to detect the presence of manateesnear structure doors, and automatic rever-sal mechanisms similar to those on eleva-tor doors. The latter option is now beingtested cooperatively by the South FloridaWater Management District and theCorps. If successful, a strategy and sche-dule to install such devices will need tobe developed and implemented.

Habitat Protection

Intensive coastal development throughoutFlorida is degrading important manateehabitat and poses perhaps the greatestlong-term threat to the Florida manatee.Three major approaches have been initia-ted to address this problem. First, theFish and Wildlife Service and the formerFlorida Department of Natural Resourcesinitiated extensive efforts to review andcomment on applications for Federal andState permits for construction projects inmanatee habitat areas. For example, pur-suant to Section 7 of the EndangeredSpecies Act, the Service now annually re-

views hundreds of permit applications tothe Corps of Engineers for constructionprojects in waters and wetlands that in-clude or are adjacent to important mana-tee habitat.

The new Florida Department of Environ-mental Protection has a similar programfor reviewing Environmental ResourcesPermits and applications for leasing stateowned submerged lands. In 1989, theFlorida Governor and Cabinet also esta-blished an interim boating facility sitingpolicy for the thirteen key counties thatlimits construction of new or expandedmulti-slip docking facilities to one powerboat slip per 100 feet of shoreline ownedor controlled by a permit applicant.

A second major approach is developingcounty manatee protection plans for the13 key manatee counties. The provisionsof these plans are anticipated to be imple-mented as amendments to local growthmanagement plans prepared pursuant tothe State's Local Government Com-prehensive Planning and Land Deve-lopment Regulation Act of 1985. In addi-tion to boat speed rules, manatee protec-tion plans are to include marina siting po-licies and other measures to protect ma-natees and their habitat. To date, oneCounty has completed its manatee pro-tection plan and plans for the other 12counties are in varying stages of deve-lopment.

A third approach to habitat protection island acquisition. Both the Fish andWildlife Service and the State of Floridahave taken steps to acquire and add newareas containing important manatee habi-tat to Federal and State protected areasystems. At the State level, several pro-

grams, most notably the Conservationand Recreational Lands (CARL) Pro-gram, have acquired important areas. Atthe direction of the Florida Governor andCabinet, special attention is given by theCARL Program to manatee habitat. Fivepercent of the CARL program budget iscurrently devoted to manatee-related pur-chases. Approximately $500 million hasbeen spent to acquire 250,000 acres who-se importance included, but was by nomeans limited to, protection of manateehabitat. Particularly important purchaseshave been made along and near the Crys-tal River, at Rookery Bay, and near BlueSpring.

The Fish and Wildlife Service also hasacquired thousands of acres of land im-portant to manatees for inclusion in theNational Wildlife Refuge System. Parti-cularly important recent acquisitions overthe past 10 years have been for NationalWildlife Refuges along the Crystal River,the Homosassa River, and the SuwanneeRiver. Both the State and the Service arecontinuing cooperative efforts with aview towards establishing a network ofcore manatee habitats throughout Florida.

Three new Sanctuaries and one of thethree existing Sanctuaries were esta-blished by the Fish and Wildlife Servicein Kings Bay within or near the CrystalRiver National Wildlife Refuge underauthority of the Endangered Species Act.In addition, a 15 square mile motorboat-prohibited area was established in the Ba-nana River within the Merritt Island Na-tional Wildlife Refuge and the KennedySpace Center.

Research

The foundation of the manatee recovery

program is detailed information on mana-tee ecology and life history. These datahave been gathered cooperatively by theFish and Wildlife Service, the formerFlorida Department of Natural Resour-ces, academic institutions, and marinezoological parks. Key elements of themanatee research program are: the salva-ge and necropsy program to monitor ma-natee mortality; radio-tagging andtracking studies using VHF and satellite-linked telemetry to define manatee move-ments and habitat use patterns; a scar ca-talogue to photographically identify indi-vidual animals and thereby determine ba-sic life history parameters such as calvingintervals, age of first reproduction, andsurvivorship; age determination studiesto develop age-specific population para-meters; studies of manatee food preferen-ces and feeding ecology; aerial surveys toidentify distribution and relative abun-dance; and a geographic information sys-tem to store, integrate, and retrieve site-specific information for myriad researchand management tasks.

Many of the above elements were pio-neered by staff of the Sirenia Project ofthe Fish and Wildlife Service's NationalEcology Research Center. The FloridaMarine Research Institute, now in theFlorida Department of EnvironmentalProtection, developed the geographic in-formation system for manatee data, andhas assumed responsibility for, or beco-me directly involved in, many of the abo-ve activities. The Federal and State agen-cies work closely with one another aswell as with cooperating researchers atvarious institutions. The Florida Depart-ment of Environmental Protection nowhas a modern, well-equipped MarineMammal Pathobiology Laboratory in St.



Petersburg, Florida that was partially fun-ded by the Fish and Wildlife Servicethrough Section 6 grant-in-aid funds. Toprovidemanagers with basic, up-to-dateinformation for making informed mana-gement decisions, continued work in allof the above areas is essential.

Rescue, Rehabilitation andRelease

Over the past five years, distressed mana-tees have been rescued at a rate of about25 animals per year in the Southeast Uni-ted States. Most rescues involve animalsseriously injured by collisions with boats,animals entangled in rope or line, orpha-ned calves judged unlikely to survive ontheir own, or animals trapped in waterconduits, such as power plants intake ca-nals or drainage pipes. Voluntary supportby marine zoological parks and othergroups is a cornerstone of the manateerescue and rehabilitation network and in-volves close cooperation among thosegroups and Federal agencies, State agen-cies, and law enforcement officials.

Initially, rescue work was authorized un-der a Fish and Wildlife Service researchpermit. However, as methods for captu-ring, transporting, treating, and maintai-ning animals were refined and the poten-tial to successfully treat and release ani-mals has increased, this work has becomemore of a management function. In addi-tion, space and resources for maintainingand treating injured manatees have beco-me a concern because some animalsjudged unreleasable have necessitatedcostly, long-term care and maintenance.Animals judged unreleasable have inclu-ded those whose injuries make survivalin the wild unlikely and calves born in

captivity or brought in as orphans whichhave not learned necessary survivalskills. A soft release facility was develo-ped at Merritt Island National WildlifeRefuge was built in 1994 to provide astaged release alternative for long-termcaptives and orphans. As of mid-1993,nearly 50 animals were in captivity atfive captive maintenance facilities in Flo-rida.

To guide rescue/rehabilitation work, theFish and Wildlife Service recently shiftedresponsibility for this aspect of the reco-very program from its former researcharm to its management staff. The Servicealso established an Interagency/Oceana-ria working group to coordinate captivemanatee management and rehabilitation,and obtained an enhancement permit un-der the Marine Mammal Protection Actto authorize related activities. The Servi-ce also developed a system authorizingthree levels of involvement by coopera-ting organizations: report verificationteams to corroborate reports of distressedanimals and to remain with animals pen-ding arrival of further help; rescue/trans-port teams to undertake hands-on rescueoperations and to transport live animals;and approved rehabilitation facilities tomaintain and treat animals.

To operate the rescue/rehabilitation net-work, the Service has issued letters ofauthorization under its enhancement per-mit outlining responsibilities of coopera-ting groups at each of these three levelsof involvement. The Service also has de-veloped criteria to guide and schedule re-lease of rehabilitated animals and conve-ned meetings of the Interagency/Oceana-ria working group to review and coordi-nate network activities. The Florida De-

partment of Environmental Protection,through the salvage and necropsy pro-gram staff at its Florida Marine ResearchInstitute, has agreed to coordinate rescueresponses by receiving reports of dis-tressed animals and arranging for theappropriate authorized participants to res-pond.

http://bluegoose.arw.r9.fws.gov/NWRSFiles/WildlifeMgmt/Specie-sAccounts/Mammals/FLManatee/FLManateeLiterature.html

Manatee Recovery PlanLiterature Cited and Bibliography

Ackerman, B. B. 1992. Ongoing aerialsurvey programs -- a progress report.Abstract. pp 14-15 in O'Shea, T. J., B. B.Ackerman, and H. F. Percival (eds.). In-terim report of the technical workshop onmanatee population biology. ManateePop. Res. Rept. No. 10. Florida Coopera-tive Fish and Wildlife Research Unit.Univ. of Fla., Gainesville. 83p.

__________, , S. D. Wright, R. K. Bon-de, D. K. Odell, and D. J. Banowetz.1992. Trends and patterns in manateemortality in Florida, 1974-1991. Abs-tract. p 22. in O'Shea, T. J., B. B. Acker-man, and H. F. Percival (eds.). Interimreport of the technical workshop on ma-natee population biology. Manatee Pop.Res. Rept. No. 10. Florida CooperativeFish and Wildlife Research Unit. Univ.of Fla.,Gainesville. 83p.

Beck, C. A. and N. B. Barros. 1991. Theimpact of debris on the Florida manatee.Mar. Pol. Bul. 22(10):508-510.

__________ and J. P. Reid. 1992. An au-

tomated photoidentification catalogue formanatee life history studies. Abstract. pp18-19 in O'Shea, T. J., B. B. Ackerman,and H. F. Percival (eds.). Interimreport of the technical workshop on ma-natee population biology. Manatee Pop.Res. Rept. No. 10. Florida CooperativeFish and Wildlife Research Unit. Univ.of Fla., Gainesville. 83p.

Beeler I. E. and T. J. O'Shea. 1988. Dis-tribution and mortality of the West Indianmanatee (Trichechus manatus) in thesoutheastern United States: A compila-tion and review of recent information.Prepared by the Fish and Wildlife Servi-ce for the U.S. Army Corps of Engineers.PB 88-207 980/AS. Natl. Tech. Inf. Ser.,Springfield, Va. 613p.

Bengtson, J. L. 1981. Ecology of mana-tees (Trichechus manatus) in the St.Johns River, Florida. Ph.D. Thesis. Univ.of Minnesota, Minneapolis. 126 p.

Bonde, R. K., T. J. O'Shea, and C. A.Beck. 1983. A Manual of procedures forthe salvage and necropsy of carcasses ofthe West Indian manatee (Trichechus ma-natus). PB83-25573. Natl. Tech. Inf. Ser.,Springfield, Va. 175p.

__________. 1983. Estimating food con-sumption of free-ranging manatees inFlorida. J. Wildl. Manage. 47:1186-1192.

Domning D. P. and L-A. C. Hayek. 1986.Interspecific and intraspecific morpholo-gical variation in manatees (Sirenia: Tri-chechus). Mar. Mam. Sci. 2(2):87-144.

Etheridge, K. G., G. B. Rathbun, J. A.Powell, and H. A.Kochman. 1985. Con-sumption of aquatic plants by the WestIndian manatee. J. Aquatic Plant Manag.



23:21-25.

Garrott, R. A., B. B. Ackerman, J. R.Cary, D. M. Heisey, and J. E. Reynolds,III. 1992. Assessing population trends atseveral Florida manatee aggregation si-tes. Abstract. pp 15-16 in O'Shea, T. J.,B. B. Ackerman, and H. F. Percival(eds.). Interim report of the technicalworkshop on manatee population bio-logy. Manatee Pop. Res. Rept. No. 10.Fla. Cooper. Fish and Wildlife ResearchUnit. Univ. of Fla., Gainesville. 83p.

Gunter, G. 1941. Occurrence of the ma-natee in the United States, with recordsfrom Texas. J. of Mamm. 22(1):60-64.

Harlan, R. 1824. On a species of Laman-tin resembling the Manatus senegalensis(Cuvier) inhabiting the coast of east Flo-rida. J. Acad. Natu. Sci., Philadelphia3:390-394.

Hartman, D. S. 1979. Ecology and beha-vior of the manatee (Trichechus manatus)in Florida. Am. Soc. MammalogistsSpec. Pub No. 5. 153p.

Hatt, R. 1934. A manatee collected bythe American Museum Congo Expedi-tion, with observations on the recent ma-natees. Bull. Am. Mus. Natu. Hist.66:533-536.

Hernandez, P., J. E. Reynolds, III, H.Marsh, and M. Marmontel. 1992. Ageand seasonality in spermatogenesis ofFlorida manatees. Abstract. p 17. inO'Shea, T. J., B. B. Ackerman, and H. F.Percival (eds.). Interim report of the te-chnical workshop on manatee populationbiology. Manatee Pop. Res. Rept. No. 10.Florida Cooperative Fish and WildlifeResearch Unit. Univ. of Fla., Gainesville.

83p.

Husar, 1977. The West Indian manatee(Trichechus manatus). U.S. Fish andWildlife Service. Wildl. Res. Rept. 7:1-22.

Ketten, D. R., D. K. Odell, and D. P.Domning. 1992. Structure, function, andadaptation of the manatee ear. pp 77-95in J. Thomas et al. (eds). Marine mammalsensory systems. Plenum Press. NewYork.

Laist, D. W. 1987. Overview of the bio-logical effects of lost and discarded plas-tic debris in the marine environment.Mar. Pol. Bul. 18(6B):319-326.

Lefebvre, L. W., T. J. O'Shea, G. B.Rathbun, and R. C. Best. 1989. Distribu-tion, status, and biogeography of theWest Indian manatee. pp 567-610 in C.A. Woods (ed.) Biogeography of theWestIndies. Sandhill Crane Press. Gainesville,Florida. 878p.

__________ and J. A. Powell. 1990. Ma-natee grazing impacts on seagrasses inHobe Sound and Jupiter Sound insoutheast Florida during the winter of1988-89. Final Report for the MarineMammalCommission. PB90-271883. Nat. Tech.Info. Ser. Springfield, Maryland. 36p.

Lowery, J. H., Jr. 1974. The mammals ofLouisiana and its adjacent waters. La.Univ. Press. 565p.

Marine Mammal Commission. 1986. Ha-bitat protection needs for the subpopula-tion of West Indian manatees in the Crys-tal River area of northwest Florida. Nat.

Tech. Inf. Ser. PB86-200 250. SilverSpring, Maryland. 46p.

__________. 1988. Preliminary assess-ment of habitat protection needs for WestIndian manatees on the east coast of Flo-rida and Georgia. Nat. Tech. Inf. Ser.PB89-162 002. Silver Spring, Maryland.120p.

__________. 1993. Marine MammalCommission Annual Report to Congress1992. Marine Mammal Commission.Washington, D.C. 227p.

Marmontel, M. 1992. Age and reproduc-tive parameter estimates in female Flori-da manatees. Abstract. pp 16. in O'Shea,T. J., B. B. Ackerman, and H. F. Percival(eds.). Interim report of the technicalworkshop on manatee population bio-logy. Manatee Pop. Res. Rept. No. 10.Florida Cooperative Fish and WildlifeResearch Unit. Univ. of Fla., Gainesville.83p.

__________. 1993. Age Determinationand population biology of the Floridamanatee, Trichechus manatus latirostris.Ph. D. Dissertation. Univ. of Fla., Gai-nesville. 408p.

__________, D. K, Odell, and J. E.Reynolds III. 1992. Reproductive biologyof South American manatees. pp 293-312in W. C. Hamlett (ed). Reproductive bio-logy of South American vertebrates.Springer-Verlag. New York.

McClenaghan, Jr., L. R, and T. J. O'Shea.1988. Genetic variability in the Floridamanatee (Trichechus manatus). J Mamm.69(3):481-488.

Moore, J. C. 1951. The range of the Flo-

rida manatee. Quart. J. Fla. Acad. Sci.14(1):1-19.

Odell, D. K. 1981. Growth of a West In-dian manatee, Trichechus manatus, bornin captivity. pp 131-140 in R. L.Brownell, Jr. and K. Ralls, eds. The WestIndian manatee in Florida. Proceedingsof aworkshop held in Orlando, Fl. 27-29March 1978. Fla. Dept. of Natu. Res., Ta-llahassee 154p.

__________. 1982. The West Indian ma-natee, Trichechus manatus Linnaeus. pp828-837. in J. A. Chapman and G. A.Feldhamer, (eds.). Wild Mammals ofNorth America. Johns Hopkins Univ.Press, Baltimore, Maryland. 1184p.

__________, J. E. Reynolds, and G.Waugh. 1978. New records of the WestIndian manatee (Trichechus manatus)from the Bahamas Islands. Bio. Conserv.14:289-293.

__________, G. D. Bossart, M. T. Lowe,and T. D. Hopkins. 1992. Reproductionof the West Indian manatee (Trichechusmanatus) in captivity. Abstract. pp 17-18.in O'Shea, T. J., B. B. Ackerman, and H.F. Percival (eds.). Interim report of thetechnical workshop on manatee popula-tion biology. Manatee Pop. Res. Rept.No. 10. Florida Cooperative Fish andWildlife Research Unit. Univ. of Fla.,Gainesville. 83p.

O'Shea, T. J. 1986. Mast foraging byWest Indian manatees (Trichechus mana-tus). J. of Mammalogy. 67(1):183-185.

__________. 1988. The past present, andfuture of manatees in the southeasternUnited States: Realities, misunderstan-



dings, and enigmas. pp 184-204. inOdum, R. R., K. A. Riddleberger, andJ.C.Ozier (eds.). Proceedings of the ThirdSoutheastern Nongame and EndangeredWildlife Symposium. Georgia Dept. ofNatu. Res. Social Circle, Georgia. 253p.

__________, J. F. Moore, and H. I.Kochman. 1984. Contaminant concentra-tions in manatees in Florida. J of Wildl.Manage. 48(3):741-748.

__________, C. A. Beck, R. K Bonde, H.I. Kochman, and D. K. Odell. 1985. Ananalysis of manatee mortality patterns inFlorida 1976-1981. J. Wildl. Manage.49:1-11.

__________, G. B. Rathbun, R. K Bon-de, C. D. Buergelt, and D. K. Odell.1991. An epizootic of Florida manateesassociated with a dinoflagellate bloom.Mar. Mamm. Sci. 7(2):165-179.

__________, and C. A. Langtimm. 1992.Adult survival estimates for Florida ma-natees at Crystal River, Blue Spring, andthe Atlantic Coast. Abstract. pp 21-22. inO'Shea, T. J., B. B. Ackerman, andH. F. Percival (eds.). Interim report of thetechnical workshop on manatee popula-tion biology. Manatee Pop. Res. Rept.No. 10. Florida Cooperative Fish andWildlife Research Unit. Univ. of Fla.,Gainesville. 83p.

__________, B. B. Ackerman, and H. F.Percival (eds.). 1992. Interim report ofthe technical workshop on manatee popu-lation biology. Manatee Pop. Res. Rept.No. 10. Florida Cooperative Fish andWildlife Research Unit. Univ. of Fla.,Gainesville. 83p.

Packard, J. M. 1981. Abundance, distri-bution, and feeding habits of manatees(Trichechus manatus) wintering betweenSt. Lucie and Palm Beach Inlets, Florida.Report to the Fish and Wildlife ServiceSirenia Project. Gainesville, Florida.139p.

__________. 1984. Impact of manateesTrichechus manatus on seagrass commu-nities in eastern Florida. Acta Zool. Fen-nica 172:21-22.

__________, and Mulholland, R. 1983.Analysis of manatee aerial surveys: acompilation and preliminary analysis ofwinter aerial surveys conducted in Flori-da between 1977 and 1982. ManateePopulation Research Report No. 2. Te-chnical Report No. 8-2. Florida Coopera-tive Fish and Wildlife Research Unit.Univ. of Fla, Gainesville. 119p.

__________, R. C. Summers, and L. B.Barnes. 1985. Variation of visibility biasduring aerial surveys of manatees. J. ofWildl. Manage. 49(2):347-351.

__________, R. K. Frohlich, J. E.Reynolds, III, and J. R. Wilcox. 1989.Manatee response to interruption of athermal effluent. J. of Wildl. Manage.53(3):692-700.

Powell, J. A. and G. B. Rathbun. 1984.Distribution and abundance of manateesalong the northern coast of the Gulf ofMexico. Northeast Gulf Science 7(1):1-2

Provancha, J. A. and M. J. Provancha.1988. Long-term trends in abundance anddistribution of manatees (Trichechus ma-natus) in the northern Banana River, Bre-vard County, Florida. Mar. Mamm.Sci. 4(4):323-338.

__________ and C. A. Hall. 1991. Ob-servations of associations between sea-grass beds and manatees in east centralFlorida. Biol. Sci. 54(2):87-98.

Rathbun, G. B., R. K. Bonde, and D.Clay. 1982. The status of the West Indianmanatee on the Atlantic coast north ofFlorida. pp 152-165. in R. R. Odum andJ. W. Guthrie (eds.) Proceedings of theNongame and Endangered Wildlife Sym-posium. Technical Bulletin WL 5. Ga.Dept. of Natu. Res. Social Circle, Geor-gia.

__________, J. P. Reid, and G. Carowan.1990. Distribution and movement pat-terns of manatees (Trichechus manatus)in north-western peninsular Florida. Fla.Mar. Res. Pub. No 48. 33p.

__________, J. P. Reid, R. K. Bonde,and J. A. Powell. 1992. Reproduction infree-ranging West Indian manatees (Tri-chechus manatus). Abstract. pp. 19-20. inO'Shea, T. J., B. B. Ackerman, and H.F. Percival (eds.). Interim report of thetechnical workshop on manatee popula-tion biology. Manatee Pop. Res. Rept.No. 10. Florida Cooperative Fish andWildlife Research Unit. Univ. of Fla.,Gainesville. 83p.

Reid, J. P. and G. B. Rathbun. 1984. Ma-natee identification catalogue October1984 update. Unpublished progress re-port prepared by the U.S. Fish andWildlife Service, Sirenia Project, Gaines-ville,Florida for the Florida Power & LightCompany. 31pp.

__________. 1985. 1985 manatee identi-fication catalogue update. Unpublished

progress report prepared by the U.S. Fishand Wildlife Service, Sirenia Project,Gainesville, Florida for the FloridaPower & Light Company. 31pp.

__________, G. B. Rathbun, and J. R.Wilcox. 1991. Distribution patterns of in-dividually identifiable West Indian mana-tees (Trichechus manatus) in Florida.Mar. Mamm. Sci. 7(2):180-190.

__________ R. K. Bonde, and T. J.O'Shea. 1992. Reproduction, mortality,and tag loss of telemetered and recogni-zable individual manatees on the AtlanticCoast of Florida. Abstract. pp 20-21. inO'Shea, T. J., B. B. Ackerman, and H. F.Percival (eds.). Interim report of the te-chnical workshop on manatee populationbiology. Manatee Pop. Res. Rept. No. 10.Florida Cooperative Fish andWildlife Research Unit. Univ. of Fla.,Gainesville. 83p.

Reynolds, III, J. E. 1992. Distributionand abundance of Florida manatees (Tri-chechus manatus latirostris) around se-lected power plants following winter coldfronts: 1991-1992. Final report preparedfor Florida Power & Light Company.Juno Beach, Florida. 41p.

__________ and J. C. Ferguson. 1984.Implication of the presence of manatees(Trichechus manatus) near the Dry Tortu-gas Islands. Florida Scientist 47:187-189.

__________ and J. R. Wilcox. 1987.People, power-plants, and manatees. SeaFrontiers 33(4):263-269.

__________ and D. K. Odell. 1991. Ma-natees and dugongs. Facts on File. NewYork. 192p.



Snow, R. W. 1991. The distribution andrelative abundance of the Florida mana-tee in Everglades National Park, an an-nual report, October 1, 1991. South Flori-da Research Center. Everglades NationalPark. Homestead, Florida. 26p.

Wright, S. D., B. B. Ackerman, R. K.Bonde, C. A. Beck, and D. J.Banowetz.1992. Analysis of Watercraft-relatedmortality of manatees in Florida, 1979-1991. Abstract. p 23. in O'Shea, T. J., B.B.Ackerman, and H. F. Percival (eds.). In-

terim report of the technical workshop onmanatee population biology. ManateePop. Res. Rept. No. 10. Florida Coopera-tive Fish and Wildlife Research Unit.Univ. of Fla., Gainesville. 83p.

Zoodsma, B-J. 1991. Distribution andbehavioral ecology of manatees insouthern Georgia. M.S. Thesis. Univ. ofFlorida. Gainesville. 202p.



http://refuges.fws.gov/NWRSFiles/Refu-geSystemLeaflets/Species/Manatee/ManateeQA.html

This publication was a cooperative effortof the Save the Manatee Club, the FloridaAudubon Society and the U.S. Fish andWildlife Service. All photos used withthis file are copyrighted by D.R. andT.L. Schrichte, Schrichte UnderwaterPhotography and used with their permis-sion. Information about these graphicscan be obtained from: [email protected]

Manatee Questions andAnswers

Call 1-800-DIAL-FMP (1-800-342-5367)or *FMP on your cellular phone if yousee an injured, dead, tagged, or orphanedmanatee, or if you see a manatee beingharassed. And Keep Our Precious MarineMammals Safe

What's wrong with feeding manatees or -giving them water?

Feeding manatees or giving them water -can result in behavior modification. Be-cause they have approached humans ex-pecting food or water, some manatees -have been harassed or fed dangerous ornon-food items. Manatees' natural fe-edingpatterns may be altered by encouragingthem to "hang around," waiting for foodor water. When hand-fed lettuce or water from a hose is no longer available, ma-natees may not know where to find oridentify natural, reliable sources of food.Feeding and watering may also adverselyaffect manatee juveniles who learn fe-eding, avoidance, migration and otherbehaviors from their mothers.

But I wouldn't harm a manatee.

Of course you wouldn't. But not everyo-ne loves manatees, and feeding manateesor giving them water could encouragethem to swim up to people who might becruel to them. Manatees have beenridden, shot at with guns and bows, hadrakes embedded in their backs, and ini-tials carved into their skin. They havebeen purposely hooked by fisherme

I need to feed the manatees. They lookhungry, and I've heard there may not beenough natural seagrass for them.

Although seagrass beds are decliningfrom pollution in many areas, there ismore than enough vegetation to sustain ahealthy manatee population in the wild inFlorida. Manatees not only eat seagrass,they eat other submerged, floating, andemergent plants.

Don't Take Lettuce Or Water FromStrangers If only we could teach manatees that rule.But we can't so it's up to us to do what'sright for manatees.

Mind Your Manatee Manners

• Practice "passive observation" and ob-serve manatees from a distance.

• Resist the urge to feed manatees or givethem water.

• When swimming or diving, "look, butdon't touch."

• "Stash your trash." Discard monofila-ment line, hooks, and other trash proper-ly.

West Indian manatees are endangeredanimals. At present, it is estimated thereare only about 2,000 of these unique ani-mals left in the United States. Since1989, there bas been an average of 174manatee deaths per year. Fully one thirdof those deaths have been attributed tohuman-related factors. Because human-related manatee deaths are preventable,this area is the most logical place to be-gin in order to reduce mortalities.

I see manatees when I'm out in the boat,and they are so cute. I want to pet them.Besides, they act like they like it.

If manatees swim up to boats, it is likelythey have been fedbefore and are expec-ting the same from you. But think aboutit-watercraft collisions are the numberone cause of human-related manateemortalities. Encouraging manatees toapproach boats makes them prone to en-counters with propellers and entangle-ment in fishing gear. Also, manatees so-metimes like to feed on the vegetationthat gets wrapped around the boat's pro-peller. Before starting up, always checkaround your boat for manatees, especiallyaround the motor area.

I always put out a hose for manatees atthe marina because they look thirsty. Sin-ce they are in salt water, I assume theyneed it.

Manatees can be found in fresh, brackish,or salt water Often, people will leave ho-ses running from their docks because it isknown that manatees are attracted tofresh water. But manatees in salt watercan go for long periods without activelydrinking fresh water. It is still not knownwhat their fresh water requirements are,

but there are many natural sources offreshwater to which they have access.

What should I do when I'm swimming ordiving and I see a manatee?

"Look, but don't touch" is the best policy.You actually have the most to gain by re-maining at a distance. If you approachmanatees, they will most likely swimaway. By quietly observing manatees,you win get a rare opportunity to see thenatural behavior of this unique animal(any other actions might be consideredharassment). When diving, switch to yoursnorkel gear and float on the surface ofthe water, as the sound of bubbles fromscuba gear may cause manatees to leavethe area. When swimming, slowly enterthe water in the presence of manatees,avoiding excessive noise and splashing.Please don't ride, chase or harass mana-tees in any way.

I don't understand how throwing a fewthings in the water can harm a great, biganimal like a manatee.

Debris in waterways, such as discardedplastic bags, six-pack holders, fishinghooks, or monofilament line is dangerousto manatees and other forms of wildlife.Litter, especially plastic litter that doesnot degrade, can get tangled in plants thatmanatees eat, and the manatee can beco-me entangled or accidentally ingest theseplastics. When a manatee swallows aplastic bag or a wad of fishing line, it canchoke them or block their intestines.Fish hooks can puncture their esophagus,stomach or intestinal lining and leads toinfection which, in turn, can lead to ill-ness or death.

My Normal Behavior



Hi, I'm your average manatee. I weighabout 1,000 pounds and am 10 feet long.I can live in fresh, brackish, or salt water.I can get sick and die if I stay too long inwaters with a temperature of less than 68degrees, so in the winter, I find a warmwater source. In the summer, I roamthroughout many of Florida's (andsouthern Georgia's) waterways. What Ineed is a clean water home, lots of natu-rally occurring plants to eat, space to tra-vel, and safe, protected areas. Can youhelp me?

Get Involved!

For more information on manatees, con-tact:

Fish & Wildlife Service,6620 Southpoint Dr., So.,Suite 310, Jacksonville, FL 32216, (904) 232-Z580 Save the Manatee Club,500 N. Maitland Ave.,Maitland, FL 32751,1-800-432-J0IN (5646)

Give To The Emergency Rescue Fund

If you would like to contribute to Savethe Manatee Club's Emergency RescueFund, call 1-800-432-JOIN (5646) for

more details. These funds will only bespent on manatee rescue and rehabilita-tion efforts.

It's The Law

Manatees are protected under federal lawby the Marine MammalProtection Act of1972 and the Endangered Species Act of1973, which make it illegal to harass,hunt, capture or kill any marine mammal.Manatees are also protected by the Flori-da Manatee Sanctuary Act of 1978.Anyone convicted of violating this statelaw faces a possible maximum fine of$500 and/or imprisonment for up to 60days. Conviction on the federal level is

punishable by a fine up of to $100,000and/or one year in prison. Feeding mana-tees, giving them water, or otherwise al-tering their behavior can be consideredharassment.

It is a second degree misdemeanor to in-tentionally discard any monofilamentfishing line or monofilament netting intoor onto the waters of the state of Florida.



The West Indian Manateein Florida

Written for Florida Power & Light Com-pany Miami, Florida By Victoria Brook Van Meter Illustrated by Laura Sartucci Wiegert

Copyright 1989, Florida Power & LightCompany

It is Florida Power & Light Company'sresponsibility to meet our customers'energy needs, and at the same time mini-mize impacts on the environment to helpprotect Florida's natural resources, wildli-fe and scenic beauty.

FPL maintains an active environmentalawareness program to demonstrate to thepublic and regulators that utility powerplants and other facilities can be built andoperated compatibly with the environ-ment.

We also want to help you understandthat industry and the environment canshare resources in a manner beneficial toboth. Plus we ask you to act responsiblyto preserve and protect the environmentand its plants and animals.

That's why FPL produces a series of

educational publications on aspects of theenvironment that we affect through ouroperations, including this one on theWest Indian Manatee in Florida. FPLoperates 13 power plants across its servi-ce territory. Manatees - an endangered

species - congregate in the warm-wateroutflow from five of these plants duringthe winter months. We have the obliga-tion to help protect these manatees for atleast two reasons. One: they are a pre-cious and increasingly rare resource. And

two: we need to prove we can build andoperate the facilities necessary to bringyou the power you demand, and protectthe animals with which we coexist.

Blue indicates general distribution of the West Indian manatee in the Caribbean.



ContentsIntroductionDescriptionEvolutionRelatedSpeciesHabitatDistributionPopulation EstimatesEconomic ImportancePastPresent

PhysiologyReproductionBehaviorActivity CyclesLocomotionFeeding

Resting and Maintenance BehaviorCommunicationSocial BehaviorSexual BehaviorCold-Related Aggregations

MortalityMan-Related CausesFlood-Control StructuresFishing GearPoaching and VandalismLoss of HabitatPollutionHarassment

Natural FactorsCold WeatherRed Tide

Legal Protection and ConservationEfforts

Outlook for the FutureAcknowledgementsAdditional Information Available from

FPLManatee Protection Zones in FloridaBoating Speed ZonesHelp Save the ManateeCitations

Introduction

The West Indian manatee or sea cow(Trichechus manatus) is a large, plant-eating aquatic mammal that can be foundin the shallow coastal waters, rivers, andsprings of Florida. These gentle creaturesare endangered throughout their range.High mortality, primarily associated withhuman activity, as well as a low repro-ductive rate and loss of habitat continueto keep the number of manatees low andthreaten the species' future.

In response to an increased awareness ofthe plight of the manatee, governmentalagencies, universities, private conserva-tion groups and concerned corporationshave joined together to promote researchand identify the actions needed to en-courage the recovery of manatee popula-tions. This work has increased ourknowledge of this species as well asraised many questions that remain unan-swered. The following presents a reviewof the current knowledge concerning thebiology, life history and status of themanatee in Florida.

Description

Manatees are large somewhat seal shapedmammals with flat, rounded tails. Adultsrange in color from gray to brown, whilecalves are darker at birth, changing to agrayish color by about one month.1Adults can reach a length of 3.9 meters(12.7 feet)2 and can weigh up to 1,500kilograms (3,500 pounds). These maxi-mum figures are unusually high. The av-erage length of a manatee is about 3 me-ters (9.8 feet) and the average weight isabout 360-540 kilograms (793-1,190pounds).3 Female manatees may tend toreach greater lengths and weights than

males.4

The Skin of the manatee is finely wrin-kled and the surface layer is continuallysloughing off, possibly to reduce thebuild-up of surface algae and othergrowths. A layer of blubber occurs underthe skin and fat deposits are found amongmuscle tissue and around the intestines.Hair is distributed sparsely over the bodyand stiff whiskers grow around the face.The manatee has no hind limbs and itsforelimbs or flippers are paddle-shaped.The bones are massive and heavy andlack marrow cavities in the ribs and longbones of the forelimbs.4 The West Indianmanatee has three or sometimes fournails at the tip of each flipper.

The face of a manatee is bulbous; thesmall, wide-set eyes give the animal aplacid expression. The nostrils, locatedon the upper surface of the snout, aretightly closed by valves when underwa-ter, and the eyes have inner membranesthat can be drawn across the eyeballs forprotection. The ear openings, located justbehind the eyes, are small and lack exter-nal lobes. The brain of the manatee issmall for a mammal of its size.5

About five hours a day are spent feed-ing on seagrasses, freshwater plants andeven plants growing along the shoreline.Manatees have a flexible upper lip that isused to manipulate food into the mouth.The teeth of manatees are unique becausethey are continually replaced. Grindingmolars form at the back of the jaw, weardown as they move forward, and eventu-ally fall out. Tooth replacement is anadaption to the manatee's diet of abrasiveplants that often are mixed with sand.The wrinkles in the surface enamel of the

molars also may help reduce wear.6 Theextreme wear of the front teeth noted inFlorida's manatees appears to be unusualand may be caused by the quartz-sandsubstrates of the Atlantic and Gulfcoasts.7

The digestive system of the manatee issimilar to that of plant eaters such ashorses, with bacterial digestion of cellu-lose occurring primarily in the hind partof the gut. This digestive system isadapted to processing large amounts ofhigh- fiber low-protein food. The intes-tines of adults can measure up to 40 me-ters (130 feet) in length. A large glandu-lar structure called the cardiac or diges-tive gland protrudes form the curvatureof the stomach. This structure producesmucus which coats swallowed food andprotects the lining of the digestive systemfrom abrasion.8 Digestion is accompa-nied by the formation of large amounts ofgas.9

The lungs of the manatee may exceed 1meter (3 feet) in length in adults and con-tain large amounts of muscle tissue.Manatees and other aquatic mammals ex-change lung air very rapidly as comparedwith similarly sized land mammals.10Both the lungs and diaphragm extend thelength of the body cavity and so are ori-ented in the same horizontal plane as amanatee. This arrangement is importantfor buoyancy control.

The main external difference betweenmale and female manatees is the locationof the urinary and reproductive opening.In the female, this opening is located justin front of the anus; in the male, it is lo-cated further forward, just behind the na-vel. Females also have a prominent teat



located against the body under eachflipper.

Evolution

Manatees belong to the order Sirenia,which also includes the manatee's relati-ve in the Pacific, the dugong. Sireniansevolved from four-footed land mammalsmore than 60 million years ago.11 Thepresence of undeveloped pelvic bones inmanatees is evidence of their terrestrialancestry.12 The closest modern relativesof the Sirenia are the elephants and smallAsian and African mammals known ashyraxes.13,14 More than a dozen sire-nian genera are known from the fossil re-cord, so this order was once much morediverse and widespread than it is to-day.15,7

The fossil record shows that both mana-tees and dugongs were once found in thenew world, but that manatees eventuallyreplaced the dugongs. Manatees mayhave prevailed because they evolvedmore wear-resistant teeth and so werebetter able to exploit developing areas offreshwater vegetation as a food source.7

Forty-five million-year-old sirenian fos-sils have been found in Florida.16 Fossildugong ribs have been discovered in sha-llow-water marine and estuarine sedi-mentary deposits throughout the state,11and manatee bones have been found inpre-Columbian Indian refuse mounds insoutheastern Florida.17

Related Species

The West Indian manatee is one of onlyfour living species in the order Sirenia. Afifth species, Steller's seacow (Hydroda-malis gigas), which grew to almost 10

meters (33 feet) in length and weighedseveral tons, was hunted to extinctionwithin 27 years of its discovery in theBering Sea in 1741. Besides its extraordi-nary size, this species was unique becau-se it inhabited cold water and fed exclusi-vely on marine algae.18

The living sirenians are tropical and sub-tropical in distribution and consist of onespecies of dugong and three species ofmanatees. The dugong (Dugong dugon)was once widely distributed but is nowrestricted to certain regions of the coastalwaters of the Indian and Pacific oceans.The largest surviving populations arefound in northern Australian waters.19

Manatees are found along the tropicalcoasts of both the eastern and westernAtlantic. The West African manatee (Tri-chechus senegalensis) is found in thecoastal waters and rivers of western Afri-ca. Very little is known about this spe-cies, and its numbers have been greatlyreduced by hunting and netting. TheAmazonian manatee (Trichechus inun-guis) is restricted to the fresh waters ofthe Amazon basin. Decimated by huntingover the past few centuries, the Amazo-nian manatee is now protected by law.However, enforcement is ineffective andthe remaining populations are subject toillegal hunting.20

Florida's manatees belong to the thirdspecies of manatee (Trichechus mana-tus), which is found from the southernUnited States to the northeast coast ofBrazil. Recent studies of skull characte-ristics have verified that manatees in thesoutheastern United States are a subspe-cies distinguishable from manatees foundin the West Indies, the Caribbean and

northeastern South America. The coolwinter of the northern Gulf coast and thedeep water and strong currents of theStraits of Florida appear to keep the po-pulation in the United States geneticallyisolated.6 The preferred common namefor the species is the West Indian mana-tee, but the subspecies found in Floridaalso can correctly be called the Floridamanatee.

Habitat

The West Indian manatee lives in fresh-water, brackish and marine habitats andcan move freely between salinity extre-mes. It can be found in both clear andmuddy water. Water depths of at least 1to 2 meters (3-7 feet) are preferred andflats and shallows are avoided unless ad-jacent to deeper water. Along the coastmanatees tend to travel in water that is 3to 5 meters (10-16 feet) deep and are ra-rely seen in areas over 6 meters (20 feet)deep.

High tides are used to reach thoroughfa-res or feeding grounds that are inaccessi-ble at low tide. Currents of over 5 kilo-meters (3 miles) per hour usually areavoided. If the water is deep enough andthe currents are not too strong, these ani-mals will travel great distances up coastalrivers. Manatees living in the upper St.Johns River are more than 200 kilometers(124 miles) from the ocean. Along thewest coast of Florida, the principal sum-mer habitats are the estuaries and grass-beds of rivers. Manatees rarely are seenin the Gulf of Mexico further than 1 kilo-meter (0.6 miles) from the mouth of a ri-ver.21

Distribution

The West Indian manatee currently isdistributed from the southern United Sta-tes through the Caribbean Islands, easternCentral America, Colombia, Venezuelaand south to Brazil's northeast coast.

Manatees can be found in freshwater,brackish and marine habitats throughoutFlorida A maximum of 62 manatees havebeen counted in Puerto Rico.22 Eightmanatees were sighted on the coast ofHaiti and it is estimated that perhaps 32liver there.23 The complete distributionof the species is not known becausemany regions within the range have notbeen surveyed in detail.

Records from the sixteenth and seven-teenth century show that the West Indianmanatee was once found as far south aslatitude 20oS, a few degrees north of Riode Janeiro. This historical range corres-ponds with the limits of the 24oC(75.2oF) mean annual isotherm.24

Florida is essentially the northern end ofthe West Indian manatee's range. Duringthe winter, cold temperatures keep thepopulation concentrated in peninsularFlorida. In the summer, however, mana-tees occasionally are reported from as farnorth as Virginia and the Carolinas. Morecommonly, manatees are seen around in-dustrial warm-water effluents in Georgiaduring the spring.25

Manatees have been sighted as far westas Texas. These individuals are probablyvisitors from Mexico and not part of theFlorida population.6 In Texas manateesightings have become less frequent asthe Mexican manatee population decli-nes, but the numbers in Louisiana andMississippi have increased as the mana-tee population of the Big Bend coast re-



gion of Florida has become more wides-pread.21

During the summer months, manateesrange throughout the coastal waters, es-tuaries, bays, and rivers of both coasts ofFlorida and are usually found in smallgroups. Studies of known individualsshow that many manatees return to prefe-rred summer and winter grounds. Mana-tees can travel great distances as eviden-ced by voyages of more than 850 kilome-ters (528 miles) between Blue Spring onthe St. Johns River and Coral Gables.Another manatee is known to have trave-led more than 230 kilometers (143 miles)from the Indian River to southern Geor-gia in only four days.26 Most traveloccurs seasonally as manatees move bet-ween summer dispersal areas and wintergathering sites but manatees may alsoshift wintering locations during a season.

Manatees inhabit the St. Johns River ba-sin throughout the year, concentrating atBlue Spring during cold winterweather.27,28 The number of manateesgathering at Blue Spring has increaseddramatically over the past 10 years duelargely to reproduction and some immi-gration.26 Some manatees that spend thesummer in the river migrate south in thewinter or congregate at warm-wateroutfalls around Jacksonville.

As many as 245 manatees have beencounted in the Indian and Banana riverarea of Brevard County during the springand 100 to 150 during the summermonths.29 Manatees may prefer the Ba-nana River because boat access is restric-ted as part of security for the KennedySpace Center complex and, therefore, themanatees are free of the harassment and

danger associated with boat traffic.26Many individuals from this region migra-te to south Florida through the Indian Ri-ver and Intracoastal Waterway for thewinter.30 A small number of manateesare reported year-round in the HobeSound and Jupiter Inlet area.31

Along the eastern coast of Florida, ma-natees are found mostly in the Intracoas-tal Waterway and lagoons but they arealso occasionally sighted offshore incoastal waters. About 50 manatees werelandlocked by salinity barriers in BlueLagoon Lake near Miami InternationalAirport until the construction of a flood-control dam allowed escape.32 Manateesare observed throughout southern Floridain the summer, particularly in Monroeand Collier counties.33 Farther north onthe west coast, manatees range up toTaylor and Wakulla counties in thePanhandle area in the summer,34 al-though the Suwannee River generally isconsidered to be the northern limit of therange.

Manatees that roam beyond Florida inthe summer and fail to return by winterrarely survive.26 As winter approaches,these tropical mammals must movetoward sources of warm water. Duringextreme drops in temperature, they re-main as close to a warm-water source aspossible and, during breaks in theweather, travel to nearby feeding areas.

It is believed that the historical winterrange of the manatee was once centeredin southern Florida, with small groupsspending the winter at a few naturalsprings in northern Florida.35,33 Overthe past 30 years, the construction ofpower plants and other industrial sites

that discharge warm water, coupled withthe loss of natural habitats, has caused ashift in manatee winter distribution.

Winter aggregations now center aroundabout 24 warm-water sources, six ofwhich are natural springs.36 As a result,manatees now winter as far north as Du-val County. In the relatively mild winterof 1979-1980, up to 100 manatees usedtwo power plants on the Indian Rivernear Titusville as winter refuges.29However, during the extremely cold win-ter of 1980-1981, only 36 manatees werecounted at the two plants. This decreaseat the northern refuges was offset by anincrease in the winter populations atpower plants farther south on the Intra-coastal Waterway, including plants at Ri-viera Beach and Port Everglades.30

On the west coast, manatees may movesouth to Collier and Monroe counties inthe winter. During aerial surveys of wes-tern peninsular Florida conducted fromJuly through November 1979, 50 to 75percent of the manatees sighted were inthese two counties.33 Manatees use seve-ral man-made warm- water sources onthe west coast; the primary one is FloridaPower & Light Company's (FPL) Ft.Myers plant near the junction of theOrange and Caloosahatchee rivers. Morethan 300 manatees have been counted atthis site during a cold spell. The depen-dence of so many manatees on this siteprompted FPL to dig artesian wells thatprovide an alternative warm-water sourcein case of a plant shutdown during coldspells.37

Several natural springs are used on thewest coast during the winter, the mostimportant of which are at the headwaters

of the Crystal and Homosassa rivers inCitrus County. There are no reports oflarge numbers of manatees in the head-waters of these rivers before the early1960s, but the number of manatees usingthese springs has doubled in less than adecade, More than 200 manatees now usethe Crystal and Homosassa river area aswinter aggregation sites. As with theBlue Spring population on the St. JohnsRiver, this increase is mostly the result ofreproduction and some immigration.26

Manatees form temporary "matingherds" consisting of a female in heat pur-sued by several males. These springs aremanaged for manatee protection andareas are set aside where manatees arefree of danger and harassment. This pro-tection, plus the currently unlimited foodsupply of exotic vegetation, has contribu-ted to the increased number of mana-tees.26 About 90 percent of the same in-dividuals return to the headwaters of theCrystal and Homosassa rivers each win-ter and six manatees have returned toCrystal River for at least 14 years.21

Manatees on Florida's east coast tend totravel farther than those on the westcoast.38 The Gulf coast lacks continuoussheltered areas for travel and the naturalsprings on the west coast provide large,reliable natural sources of warmth andabundant food.21 Manatees do not seemto move from one coast of Florida to theother. Travel across Florida through theOkeechobee Waterway has not been do-cumented nor do manatees appear tocross Florida Bay. However, no regionalgenetic differences have been detectedand so some gene flow must occur acrossthe peninsular.39 The number of mana-tees on the Atlantic and Gulf coasts is



about equal.26

Population Estimates

There is no evidence that manatees wereonce much more abundant in Florida thanthey are now or that they ever nearly be-came extinct. Manatee bones are relati-vely scarce in pre-Colombian Indian re-fuse heaps indicating that manatees wereprobably not abundant.36 Genetic studiesalso show that manatees have relativelyhigh genetic variability as compared withspecies whose numbers have been greatlyreduced.39 During the past 30 years ma-natees have become more widespread,and, possibly even more numerous, inFlorida as a result of protection, the in-crease in winter refuges and the introduc-tion of exotic vegetation.26

No one knows the exact number of Flo-rida manatees but intensive winter aerialsurveys at warm-water refuges in 1992counted a minimum of 1,856. This num-ber is higher than previous estimates be-cause of improved survey methods cou-pled with favorable weather conditionsduring the survey. Manatees are difficultto count because they are often found inareas of poor visibility and they tend tocluster together at warm-water sources.As a result, the size of the total popula-tion is difficult to determine. Manateesare so longlived and reproduce so slowlythat it may take many years before trendsbecome evident. Locally, however, themanatees at a few natural springs havebeen studied for several years and gene-ralizations as to population trends can bemade.

In northeast Florida, the number of ma-natees may be declining as a result of thechronic loss of adult manatees to boat

and barge collisions coupled with low re-productive rates.40 However, on the westcoast of Florida, particularly around theBig Bend region, the population appearsto have increased. Mortality is low com-pared to other parts of the state, there is arelatively large percentage of calves, andsome manatees are emigrating from thesouth. The introduction of exotic fresh-water plants such as hydrilla also has in-creased the amount of food available.This hopeful news must be tempered bythe reports of some researchers that thegrowth of recent decades has slowed inthe past few years.41 With the exceptionof the Everglades, the Big Bend area isthe least developed part of Florida'scoastline, making it critical to the long-term outlook for the manatee in Flori-da.21

The percentage of calves in Florida'smanatee population is relatively low.Surveys in southwest Florida, a center ofmanatee abundance, found that only 4.9percent of the manatees were calves. Thisfigure was lower than that found in ear-lier counts.33 In a survey of northeastFlorida, 7 percent of the manatees werecalves.40 Aerial survey counts of mana-tees at warm-water refuges during coldwinter weather show that from about 9 to13 percent of the animals are cal-ves.30,42 These figures may reflect atendency for females with calves to seekout warm-water refuges more than otheradults. It is not known if the birth rate ishigh enough to offset the 120 or so deadmanatees recovered annually in Floridain recent years.

Economic Importance

Past

The manatee has been hunted for thou-sands of years for meat, bone, hides andfat. Manatees were well-known amongprehistoric Indians as evidenced by theuse of ceremonial pipes in the form ofmanatees.43 Hides were made intoleather shields, cords and shoes, and theivory-like bones were believed to be ofmedicinal value.44 Florida Indians hun-ted manatees as a supplement to their dietand may have sold excess meat to theSpanish.45

In the seventeenth century, shiploads ofdried manatee meat were shipped fromthe Guianas to feed sugar plantation labo-rers in the Caribbean.46 Pioneers arrivingin the nineteenth century shot manateesfor meat, oil and hides, and poaching wascommon in parts of Florida during theDepression and World War II. CowpensKey in the Florida Keys is thought to beso named because manatees were oncepenned in a small cove there as a foodsupply.

Despite many centuries of hunting byprehistoric Indians and, later, by Euro-peans, manatees in Florida were neversubjected to the intense commercial ex-ploitation experienced by South Ameri-can manatee populations.7,26 This hun-ting, which continues today in manycountries, eliminated manatees frommany parts of their former range. Aboutthe only hope for manatees in many poorcountries is that, as hunting expertise di-sappears with the older generation, thesepopulations can grow.23

Present

It has been suggested that manateescould be raised commercially for theirmeat, but their endangered status and lowreproductive rate make this unlikely.Another proposal was that manateescould be of value in controlling aquaticweeds that are a problem in many partsof the world, including Florida.47,48However, recent studies have shown thatmanatees do not eat enough to be effecti-ve plant control agents.49 It has been cal-culated that about 3,000 manatees wouldbe needed just to maintain a constantamount of hydrilla in the 165 hectares(408 acres) of the headwaters of CrystalRiver.50

We now realize that the value of the ma-natee goes beyond its use for meat pro-duction or weed control. The manateehas been an integral part of Florida's eco-logy for millions of years and has theright to survive. The sight of one of theseanimals in its natural habitat is a memo-rable experience, whether for the Floridaresident or the visitor enjoying one ofFlorida's many waterways. It is difficultto put a dollar figure on ecological valueor aesthetic appeal, but, clearly, manateesare an important asset and an attractionunique to Florida.

Physiology

Little is known about the physiology ofmanatees and current studies are restric-ted because of the risk of working withendangered animals. The manatee's meta-bolic rate is unusually low comparedwith other mammals, which in part mayaccount for its susceptibility to cold51and slow healing rate.52 A low metabolicrate is adaptive for a large tropical animal



that must keep cool and that lives on a re-latively poor quality diet. However, thisadaption can be a liability for populationsat the northern edge of the species' rangewhere metabolic heat is needed to main-tain body temperature. The manatee'sbody temperature is reported to be36.4oC (97.5oF) but this may vary seaso-nally or with water temperature.

Manatees ar rest have a relatively lowheart rate of 50 to 60 beats per minute.During a prolonged dive, the rate maydecrease to about 30 beats per minute.53Dives of up to 24 minutes in durationhave been reported,32 although thelength of time between breaths usuallyranges from about four minutes whileresting to half a minute during strenuousactivity.54 The interval between breathsis prolonged by replacing a large percen-tage of the air in the lungs with eachbreath.

It is known that manatees are long-livedbut no adequate method of determiningage has been developed. One manateehas been maintained in captivity for al-most 40 years.

Reproduction

Female manatees may reproduce as earlyas 4 to 5 years of age but at such an earlyage may be unsuccessful at raising cal-ves. Most females breed successfully by7 to 9 years of age.2 The smallest femaleknown to have given birth was 2.6 meterslong (8.5 feet).4

Manatee calves nurse underwater andmay remain with their mothers for morethan two years. The gestation period ofthe manatee is about 13 months and fe-males usually produce one calf with each

pregnancy. Twins occur occasionally andfemales may care for orphaned calves.54The interval between births is probably 3to 5 years, although a female losing hercalf soon after birth could have anothercalf within two years. Calving occursthroughout the year.34 Newborn calvesrange in length from 1.2 to 1.4 meters (4to 4.5 feet) and weigh about 30 kilograms(66 pounds).4

Calves remain dependent on their mo-thers for up to two years. The young nur-se underwater for about three minutes ata time from teats located at the junctionof the forelimbs and the body. Manateemilk contains more fats, proteins and saltthan cow's milk and does not contain lac-tose.55 Manatees are born with premo-lars and molars, and as a calf begins toeat plants, the mechanical stimulation ofchewing causes the teeth to move for-ward about 1 millimeter (.03 inches) amonth. The front teeth wear down andeventually fall out to be replaced by theteeth moving forward.56 Calves beginnibbling on plants within a few weeks ofbirth.

Research suggests that mothers and theiryoung recognize each other beyond wea-ning and the some offspring spend atleast their subadult lives within the rangeof their mother. This may enhance survi-val by enabling manatees to learn migra-tion routes and the location of winter re-fuges and feeding grounds.57

Behavior

The behavior of manatees may appearsimple, but it is well suited to the needsof these animals. Manatees evolved in re-gions with plentiful food supplies andfairly constant temperatures and so have

never needed to develop complex beha-viors to obtain food or protect themselvesfrom the elements. Furthermore, becausemanatees have no natural enemies theironly defense is to swim away. The lackof major environmental stress also is re-flected in social behavior. Since mana-tees do not need to work together to ob-tain food or deter predators they have arelatively unstructured social life.54

Activity Cycles

Manatees do not have any set daily rou-tines and will feed, rest and performother activities throughout the day andnight. However, during winter coldspells, activities such as feeding tripsmay be regulated by diurnal temperaturecycles. Extensive studies at Blue Springrevealed that manatees would leave theconstant- temperature spring run in lateafternoon to feed in the St. John Riverand return in the early morning, thus con-serving energy by leaving the spring runwhen the river was at its warmest. Thisroutine ceased with warm springweather.27 Manatees also have been re-ported to time their activities to avoid ha-rassment by boats or divers.32,58

Locomotion

Manatees move forward by undulatingtheir tails and steering with their tails andflippers. They are neutrally buoyant inthe water and can move vertically in thewater, apparently by changing the volu-me of air in the lungs by muscular con-traction or relaxation.59

Manatees are surprisingly agile under-water and can perform maneuvers suchas somersaults, barrel rolls, head and tailstands and upside-down gliding. Al-

though clocked at speed of up to 25 kilo-meters (15 miles) per hour for shortbursts, manatees generally cruise at spe-eds of 4 to 10 kilometers (2-6 miles) perhour.54

Feeding

Manatees spend about five hours a dayfeeding and in that time consume about 4to 9 percent of their body weight in wetvegetation.69,49 Vegetation is graspedand torn by the lips, which are strengthe-ned with lateral, horny pads, and thenpassed back to the grinding molars. Sto-mach content analyses show that food iswell-chewed.61 Manatees feeding in aseagrass bed either crop the seagrass lea-ves or dig into the sediment with theirflippers to eat the rhizomes or roots aswell as the leaves.31 Much of the bio-mass and carbohydrates in seagrasses isconcentrated in the below-ground portionof the plant. In areas where manatees areconcentrated, such as near warm-waterrefuge, digging up rhizomes can result inthe temporary disruption of seagrassbeds. However, there is no evidence tosuggest that manatees have a damagingeffect on grassbeds.

Manatees are often seen feeding at theedge of seagrass beds, possibly becausenearby deeper areas offer an escape routeif disturbed. Protection from wind andcurrents is preferred, so manatees will of-ten chose feeding sites behind barrier is-lands.62 Birds, such as little blue herons,sometimes feed on the fish and inverte-brates flushed out of vegetation bybrowsing manatees.63 Just before winter,manatees living in the St. Johns Riverand Blue Spring increase the amount oftime spent feeding. Manatees need large



amounts of food in winter because moreenergy is required to maintain body tem-perature in cooler water and winter fora-ge may have a lower caloric value.60Manatees may also fast, especially duringcold weather. Several manatees observedin Blue Spring during a cold spell did notfeed for over a week.27

Manatees are opportunistic feeders andmany kinds of plants are eaten in the wildand in captivity. Some researchers havesuggested that manatees will eat anyplant soft enough to be torn by the mus-cular upper lip, and a varied diet is pro-bably necessary to meet nutritional requi-rements. However, some plants such asspatterdock are clearly avoided, possiblybecause they taste bitter.27 Submerged,emergent and floating vegetation, in thatorder, appear to be the preferred food ofmanatees. The orientation of the mana-tee's mouth is particularly adapted to fe-eding on bottom vegetation.64

Manatees can crawl partway onto a bankto reach shoreline vegetation and, at BlueSpring run, manatees have been observedfeeding on acorns that fall to the river bo-ttom from overhanging live oak trees.Acorns can be a nutritious source of foodin early winter when aquatic vegetation issparse.65 Manatees also incidentally eatinvertebrates, which may supply neededprotein. In captivity, manatees will rea-dily accept fish; in Jamaica they havebeen observed eating fish captured in fillnets.66

Manatees may or may not need freshwa-ter to survive, but they frequently are re-ported drinking freshwater from hoses,sewage outfalls and culverts in salineareas.29

Resting and Maintenance Beha-vior

Manatees rest from 2 to 12 hours a dayeither suspended near the surface or lyingon the bottom, usually for several hoursat a time. If resting on the bottom, theysurface to breathe in an almost hypnoticstate. On cold days when surface watersare warmer, manatees tend to rest at thesurface. Manatees usually spend less thanfive minutes at a time underwater,62 butbottom resting for almost 12 minutes hasbeen reported.54

Manatees often clean their mouths withtheir flippers and root in sand or mud bo-ttoms. They also rub themselves againstlogs, rocks, ropes and even the hulls ofboats. Females tend to rub more than ma-les and the parts of the body rubbed oftenare places where glandular secretionsmay be produced such as the genitals,around the eyes, armpits and chin. Thisscratching may just be to relieve itching,but it has been speculated that it mightserve to leave a scent message as to thepresence and reproductive condition ofresident females. Males traveling overlarge areas could check traditionalrubbing posts to assess the receptivity oflocal females. This would assure that fe-males would have a wide selection ofmates.67

Manatees rest at the surface or on thebottom for many hours each day, surfa-cing only to breathe. While resting on thebottom, some manatees lie on theirbacks.

Communication

Manatees communicate through sound,

sight and probably taste, touch and smell.Despite the absence of external ears andthe small size of the auditory passage,manatees hear very well, including a cer-tain degree of ultrasonic reception.68Manatee cows will respond to the squealsof their calves from more than 60 meters(almost 200 feet) away, and adult mana-tees have been reported to home in onsounds from 50 meters (160 feet)away.54

Manatees emit a range of sounds under-water that are within human auditory ran-ge. These sounds are believed to be usedfor communication and not for echoloca-tion or navigation.69 Indeed, manateesmay bump into objects in murky wa-ter.70 Manatees make sounds when theyare frightened, sexually aroused or pla-ying, and vocalization plays a role inmaintaining contact between adults andbetween cow and calf. A cow and hercalf separated by a flood gate vocalizedconstantly for three hours until the damwas opened.32 Calls are used to maintaincontact while feeding and traveling, par-ticularly in turbid water. Rapid callinghas been noted when a group is startledand flees an area and manatees appear togreet new arrivals with rapid vocaliza-tions.71 Information can be conveyed byvarying the pitch, loudness and durationof calls.67

Manatees will investigate objects visua-lly, although depth perception seemspoor at close range. In very clear water,manatees respond to visual cues fromdistances of 35 meters (115 feet).54 Thepresence of two types of cone cells in theretina suggests that manatees can see incolor.72

Touch, taste and smell also may beforms of communication as manatees fre-quently make body contact and moutheach other.54 Manatees also seem able todiscriminate preferred foods through tas-te.27

Social Behavior

The manatee has been described as "amildly social, essentially solitary ani-mal.54" Except for the relationship bet-ween a cow and her calf, most associa-tions appear temporary. However, conti-nuing research is revealing that social in-teractions may be more complex thanpreviously thought.

Manatees are not territorial or aggressiveand individuals within a group do not do-minate others. Groups seem to form ca-sually without regard to sex or age, withthe exception of cow-calf pairs andgroups of juvenile males that form tem-porary bachelor herds as a result of theirexclusion from reproduction.32

"Kissing" may be a form of communi-cation between manatees.

Although individuals within a group donot exhibit dominance, an individual mayinitiate an activity that others will follow.Manatees in Blue Lagoon Lake wereseen bodysurfing together in flumes crea-ted by a salinity intrusion barrier. Fouradults, following the lead of a fifth mana-tee, bodysurfed for over an hour, withfrequent vocalizations and nuzzling bet-ween rides.32

Other forms of social interaction include"kissing," mouthing, bumping and cha-sing. Juvenile males sometimes instigateplay with juvenile or adult females that



suggests sexual activity. Manatees mayplay for hours but generally only afterthey have fed and are not harassed.

Sexual Behavior

While female manatees do not form per-manent associations with males, duringestrus or heat, a cow will be pursued bycourting bulls. This "mating herd" mayremain together from a week to a month.Juvenile males may join and leave theherd but a nucleus of mature, persistentbulls will remain.54 The males may esta-blish a dominance order for matingrights. Females have a long estrous pe-riod that allows time for many males togather and increases the number of po-tential mates.67 During most of the cyc-le, however, females attempt to flee andavoid the persistent bulls. When the fe-male is receptive, she will copulate withone or more males in succession. Copula-tion is brief and occurs in an abdomen-to- abdomen position with the male be-low; in shallow water, a side-to-side po-sition may be used.

In studies of the summer movements ofmanatees in the St. Johns River system,radio transmitters were used to track indi-vidual manatees.27 Adult males werefound to systematically patrol and searchsections of the river system in "circuits"lasting several days. Adult females,however, unless in estrus, stayed withinrelatively small home ranges along well-traveled routes. These contrasting travelpatterns may serve a reproductive func-tion. The behavior of the males allowsthem to maintain contact with many fe-males and increases the chances of loca-ting a female in estrus. Likewise, the fe-male's behavior increases the likelihood

of contact with males. As the female inestrus travels with males in pursuit, addi-tional males are attracted for mating.

Cold-Related Aggregations

Between November and March eachyear, large numbers of manatees in Flori-da converge on sources of warm water.Individuals may come and go or move toother refuges throughout the winter.Warm-water refuges may be essential tomanatee survival, particularly in northFlorida. However, in winter not all ofFlorida's manatees can be accounted forat warm-water refuges. Some manateesmay take refuge in coastal waters or pro-tected bays where temperature fluctua-tions are minimal; groups of manateeshave been reported in the Everglades Na-tional Park during cold snaps.73

The air and water temperatures associa-ted with the arrival of manatees at warm-water refuges seem to vary with the loca-tion of the refuge and possibly the timeof year. Air temperatures below 10oC(50oF) and water temperatures below 21-22oC (70-72oF) are correlated with thearrival of manatees at Crystal River andBlue Spring.54,27,28 At a power planton the east coast, water temperatures of15oC (59oF) were associated with largemanatee aggregations.31

Irregular feeding of manatees is noted at18-19OC (64-66OF)

Manatees may acclimate to cold tempe-ratures as the season progresses. Re-search has shown that air temperatures of10oC (50oF) prompted aggregations atCrystal River in November, but tempera-tures near 5oC (41oF) were needed befo-re manatees sought warm water in

March.54 A similar seasonal pattern alsohas been noted in studies at power-planteffluents. However, the decrease in thetemperature associated with aggregationsnear warm water may reflect an increasedneed for feeding trips rather than accli-mation.74 Manatees may be able to feedin cold water if they can move to warmerwater for digestion.75 Energy storesappear to decrease over the winter as evi-denced by the thinning of the fat layer.51

The threshold of cold tolerance has notbeen well established, but the 20- 23oC(68-73oF) temperatures found at the win-ter refuges is near the lower thermal neu-tral limit proposed for manatees.75 Workwith captive manatees has shown that ac-tivity decreases with lower water tempe-ratures. Irregular feeding is noted at 18-19oC (64-66oF) and feeding may ceasecompletely as temperatures approach10oC (50oF). The minimum temperaturesuitable for manatees generally is belie-ved to be 19oC (66oF). However, mana-tees have been observed in water as coldas 13.5oC (53oF) with no ill effects.54Undoubtedly, cold tolerance varies withage, health, vigor, activity and reproduc-tive state of the individual.

Mortality

Over the past centuries, the principalsources of manatee mortality have beenopportunistic hunting by man and deathsassociated with unusually cold winters.Today poaching is rare, but high morta-lity rates from human-related sourcesthreaten the future of the species.

A primary focus of research and conser-vation efforts has been to identify andquantify manatee mortality. Since theprogram began in 1974, more than 1,000

dead manatees have been recoveredthrough the Manatee Salvage Program.Additional manatee deaths were verifiedbut carcasses were not recovered and,presumably, other dead manatees werenever found or reported. These statisticssupport the belief that reducing mortalityis the fastest and most direct method ofstabilizing or increasing manatee popula-tions.76

Man-Related Causes

Information gathered through the Mana-tee Salvage Program has led to the identi-fication of some of the causes of manateemortality. Over 30 percent of the deathsfor which a cause was determined wereattributed to human activities. These arediscussed in decreasing level of impor-tance.

Boats and Barges

The largest single mortality factor is co-llision with boats and barges. The pri-mary culprit is large boats over 7.3 me-ters (24 feet) long with inboard motorsand propellers over 38 centimeters (15inches) in diameter.77 However, small,fast-moving boats also kill manatees.Barges moving through shallow water ordocking often crush manatees that haveno room to escape. Most manatees inFlorida bear scars or deformities from be-ing run over by boats. These scars are socommon and distinctive that they areused in research for long-term recogni-tion of individuals. Over 900 individualmanatees have been catalogued by dis-tinctive scars.78.2

About half of the manatees killed byboats do not have fresh propeller marks,indicating that they were killed by impact



rather than propeller cuts. Manateescannot escape fast boats, and there maynot be enough clearance to get out of theway even when a boat is movingslowly.77 Some researchers have notedthat manatees do not necessarily avoidareas with heavy boat traffic and mayeven become habituated to the sound ofboats.31,32 Eighty percent of all deathsfrom boat/barge collisions occur in eas-tern Florida, particularly Brevard Countyand the St. Johns River.40,79

A massive effort by the state of Florida,the U.S. Fish and Wildlife Service(USFWS) and private organizations isunderway to educate the boating public.Regulation of boat speeds and boat ex-clusionary areas are being enforced to re-duce boat-related injuries and harass-ment. However many waterways used bymanatees are not protected. Manatees re-gularly travel through the IntracoastalWaterway and the St. Johns River, inclu-ding the main channels, as they migrateand so must contend with heavy boat andbarge traffic. The effect of boats on ma-natee populations is particularly criticalbecause it is mostly adults that are killed.Manatees need to maintain a high adultsurvival rate because they reproduce soslowly.79 The use of propeller guardsmay reduce injuries and deaths but sinceso many deaths are caused by impactwith large boats, it has been calculatedthat no more than nine deaths a yearwould be prevented.79

Boat-related mortality is probably thegreatest single threat to the manatee.Efforts by the USFWS, the Florida De-partment of Natural Resources and theArmy Corps of Engineers to limit dredgeand fill permits and control the size and

location of marinas are directed towardthis problem.

Flood-Control Structures

Manatees also are killed in flood gatesand canal locks. This problem was parti-cularly acute in Dade County, where au-tomatic flood-control dams were killingmore manatees than was boat traffic.80Investigations of how manatees were ki-lled in these structures led to the imple-mentation of modified operating proce-dures. These inexpensive modificationshave reduced this cause of mortality.79

Boat and barge collisions are responsi-ble for many manatee deaths each year.Almost all manatees in Florida bear scarsor deformities from being hit by boats.

Fishing Gear

Another cause of death is entanglementin or ingestion of fishing gear.81,82 Ma-natees often are seen with fishing hooksand lures imbedded in their lips and,occasionally, crabtrap lines may knot sotightly around their flippers that severeinfections, amputation or death may re-sult. Hoop nets formerly used by com-mercial fishermen in the St. Johns Riverwould sometimes drown calves but theuse of a simple excluder device appearsto have solved this problem.

Poaching and Vandalism

Poaching and vandalism account for afew manatee deaths a year. However,with continued public awareness and lawenforcement, the number of these deathsshould be further reduced.

Loss of Habitat

Loss of habitat is one of the most seriousthreats to the manatee, as it is for all ofFlorida's wildlife. Many freshwater andmarine grassbeds have been reduced oreliminated by water pollution, herbicides,dredge and fill projects and surface ru-noff. Formerly productive areas, inclu-ding north Biscayne Bay and parts ofTampa Bay, have been extensively modi-fied by human activity and many naturalwarm-water areas have been affected byloss or reduction of artesian flows.

Explosives used to widen the Miami Ri-ver in 1943 killed at least 100 mana-tees,35 although the effects of deve-lopment are usually less dramatic. Unpre-cedented human population growth andassociated boat traffic along Florida'scoasts and waterways have degraded andeliminated manatee habitat. There arenow few places where the manatee is freefrom the danger and harassment posed byboats and other human activities.

Pollution

Pesticides, herbicides and industrial che-micals from ingested water and vegeta-tion can accumulate in manatee tissue.Some studies have shown that pesticideresidues in manatee tissue are below thelevels of pathologic significance and thatmanatees are relatively uncontaminatedby organochlorines, lead or mer-cury.83,81

Other analyses, however, have revealedthat some manatees have high concentra-tions of copper in their tissue, probably -as a result of feeding on vegetation trea-ted with copper-based herbicides.83 Thelevel of copper in the diet of manateesnormally is very low so there may be no

physiological regulating mechanism toprevent the accumulation of copper in theliver. Copper-based herbicides were oncewidely used in areas where manateesgather. In one year alone, six tons of ele-mental copper were applied to the CrystalRiver system.83 Herbicide spraying isnow restricted during times when mana-tees gather and the use of alternative con-trol measures such as mechanical harves-ting is encouraged.

Ingestion of pollutants may cause a ran-ge of sublethal effects that can reducemanatee viability. This is of particularconcern in view of the potential for oilexploration on the outer continental shelfof both coasts of Florida. Many impor-tant coastal manatee habitats would bevulnerable to an offshore oil spill.

Harassment

Manatees frequently are disturbed byshin divers, boaters and fishermen. Thenoise pollution associated with boats dis-rupts vocal communication among mana-tees and boat traffic can interrupt matingactivity.67 Although some manatees willseek the attention of divers, most willavoid humans. Harassment, particularlyin warm-water refuges, forces manateesto use less-preferred or marginal habitatand subjects them to the possibility ofcold-related illness.

Manatees cannot escape fast boats, andthere may not be enough clearance to getout of the way even when a boat is mo-ving slowly. Regulation of boat speedsand boat exclusionary areas are being en-forced to reduce boat-related injuries andharassment.

Natural Factors



Cold Weather

Reports of manatee deaths often followunusually cold weather, as occurred inthe winters of 1977, 1981 and 1984.79The presence of man-made warm-watersources in central and northern Floridamay cause some manatees to winter inareas that during severe winters are toocold for their needs. However, winterdeaths are geographically widespreadthroughout Florida and not concentratedaround plants or other winter refuges.79

The reasons for cold-associated deathsstill are not clear. It was once thoughtthat cold made manatees more suscepti-ble to diseases such as pneumonia, butrecent studies suggest that most cold-re-lated deaths are not due to disease. Ins-tead, during severe winters, affected indi-viduals cannot produce enough metabolicheat to make up for heat loss to the envi-ronment. These animals have reduced fatreserves and show general physical was-ting as from malnutrition.84,79 At watertemperatures below 16oC (60.8oF), cap-tive manatees become lethargic and stopeating.85

Young in their first year of independen-ce account for many winter deaths. Thesusceptibility of the young may be due totheir smaller size which causes them tolose more body heat than larger animals.Because of their inexperience with tradi-tional migration routes, they also may be-come stranded in cold water, becomelethargic and stop eating.79

Red Tide

During the spring of 1982, at least 37manatees died in Lee County in the lower

Calooosahatchee River and San CarlosBay in association with an outbreak ofred-tide. Many of the dead manatees hadingested large numbers of small marineanimals, known as ascidians or seasquirts, that may have accumulated to-xins from the red-tide organisms. The seasquirts were probably ingested incidenta-lly as the manatees fed in seagrassbeds.84 These manatees also may havebeen exposed to airborn toxins from redtide as they breathed at the water's surfa-ce.

Legal Protection and Conserva-tion Efforts

Florida was established as a manateesanctuary by the English as early as theeighteenth century. In 1893, a Floridalaw was established to protect manatees,and since 1907 there has been a fine of$500 for a person who kills or molestsone. In July 1978, protection was increa-sed significantly when the "Florida Ma-natee Sanctuary Act" was passed by thestate. This act established the entire stateof Florida as a "refuge and sanctuary forthe manatees" and allowed for enforce-ment of boat speed regulations in desig-nated areas. State responsibility for ma-natee protection is vested with the Flori-da Department of Natural Resources(DNR) and the Florida Game and FreshWater Fish Commission.

Manatees are protected at the federal le-vel by the Marine Mammal ProtectionAct of 1972 and the Endangered SpeciesAct of 1973, as amended. The Endange-red Species Act makes it a violation to"harass, harm, pursue, hunt, shoot,wound, kill, capture, or collect endange-red species." Violations can result in fi-

nes of up to $20,000 and/or up to oneyear in prison. The law also prohibits theimportation or exportation of endangeredspecies or their parts or products. Federallegislation is administered by the U.S.Fish and Wildlife Service (USFWS) incooperation with state agencies. Manystate law-enforcement officers have beenfederally deputized so that they can en-force the federal as well as state laws.

Many federal, state and private groupshave joined in the effort to protect themanatee. The USFWS (through the Na-tional Ecology Center) is directing itsefforts toward research. In 1974, thisagency began the Sirenia Project to planand conduct the basic research needed toprotect the species. The Manatee SalvageProgram, begun as part of this project,provides a network for reporting and re-covering injured or dead manatees. Treat-ment for injured animals is provided byprivate oceanaria and dead manatees aresalvaged for necropsy. This program,which is now under the direction ofDNR, has provided valuable informationon manatee mortality as well as speci-mens for research. The USFWS is alsoresponsible for establishing manatee re-fuges and sanctuaries; these efforts areperformed under the authority of the En-dangered Species Act and the FloridaManatee Sanctuary Act.

Twenty-two manatee wintering sites arenow manatee protection zones includingKings Bay at the headwaters of CrystalRiver and Blue Spring on the St. JohnsRiver. Boat speeds are curtailed in mana-tee protection zones; in areas designatedas refuges, no boats, swimmers or diversare permitted.

To determine how to meet the goals ofrecent legislation, the USFWS led agroup of state and private agencies in de-veloping the "West Indian Manatee Re-covery Plan" to identify the actions nee-ded to "prevent further decline and to en-courage recovery of manatee populationsin U.S. waters.76" This plan sets priori-ties for research and management andpresents a schedule for implementing theobjectives of the plan.

Manatee protection must be addressed atthe regional, county and local levels. TheDNR, in concert with the USFWS, worksclosely with regional planning councils,county planners and city officials to in-clude manatee protection in log-termplanning. Marine industry representativesand boating interests have also been en-listed in determining how to balance theneeds of boaters with manatee safety.

In 1978-1979, radio-tracking was usedto study manatees in the St. Johns Riversystem.27 Later, techniques were develo-ped to monitor the movements of mana-tees in saltwater areas. This method usesa VHF or satellite-monitored transmitterattached to a 2-meter long (6.5 foot)tether that is belted around the tail of amanatee. The long tether allows thetransmitter to float at the surface, thusavoiding the problems of attenuation ofsignals in saltwater. The belt bucklearound the manatee is designed to even-tually corrode and fall off and the tetherwill pop off if a manatee becomes entan-gled. The location of the manatee, acti-vity information, and water temperatureare plotted from satellite information andverified by boat or shore observation.

Satellite radios are expensive but the te-



chnology is improving and much valua-ble information is being gathered on ma-natee movements. VHF radios are not ex-pensive but require extensive man powerto track the animals. One problem en-countered in tracking studies is that manytags are being removed by bystandersunaware of the telemetry research. Theequipment is not dangerous or stressful tothe animals.86

The best plans are ineffective if the pu-blic is not sufficiently informed tosupport conservation efforts. In responseto this, the DNR and conservation orga-nizations conduct a variety of public-awareness programs on manatee conser-vation. The DNR operates a ResourceAlert number to receive reports of mana-tee injuries, deaths, tag sightings or ha-rassment. The number, for the stat of Flo-rida only, is 1-800-DIAL-FMP (342-5367).

Private organizations contribute greatlyto conservative efforts. The Save the Ma-natee Club is located at 500 N. MaitlandAve., Maitland, FL 32751, (407-539-0990). With over 27,000 members, thisgrowing organization focuses on promo-ting public awareness of the manatee andfunding research and conservation pro-jects. Private oceanaria in Florida havespent millions of dollars in rescuing andrehabilitating manatees. This work hasled to an improvement in manatee hus-bandry methods and yielded importantinformation on life history.

Florida Power & Light Company (FPL)is an important contributor to manatee re-search and conservation efforts. Fundedby FPL, the Florida Audubon Society,and, more recently, Eckerd College have

conducted aerial surveys to monitor ma-natee populations and identify importanthabitats. A USFWS investigation of themanatees' winter use of two power planteffluents on the Indian River in BrevardCounty was also funded by FPL. The on-going projects of cataloging distinctivelyscarred manatees and radio-tracking ani-mals are also supported. In addition, FPLsponsors public-awareness and educatio-nal programs, distributes booklets andfilms, and supplies bumper stickers thatdeclare "I Slow for Manatees."

Many manatees take refuge during coldweather in the warm-water discharges ofpower plants.

Outlook for the Future

The extinction of all sirenians is a dis-tinct possibility. The tragedy of this isthat the conservation of the manatee, par-ticularly in Florida, poses such an idealchallenge. The manatee in the UnitedStates does not present the internationalconflicts such as posed by whaling, doesnot conflict with fishing interests, is notused by indigenous people for subsisten-ce, is not dangerous, and in fact, is atourist attraction.87 Manatees are adapta-ble animals that eat a wide range ofplants and move readily between freshand saltwater habitats. They do not requi-re large wilderness areas and, when nothunted, lose their fear of man and caneven live in heavily developed urban en-vironments.26 The primary conflictappears to be with boating-related activi-ties.

As one of the most affluent and conser-vation-minded nations in the world, weshould be able to coexist with this docilemammal.87 If we cannot save the mana-

tee in the United States, it sets a poorexample for Third World countries underpressure to preserve habitat and wildlifewhere the issues can be much more com-plex.

Wildlife management is really peoplemanagement. In Florida the problem isone of preserving habitat and travelwaysin the face of an ever increasing numberof people, marinas, boats, divers and wa-terfront developments.88 Research andconservation efforts by many cooperatingpublic and private groups raise hopes thata way may be found to ensure the survi-val of the manatee. The establishment ofrefuges and sanctuaries, enforcement ofboat speed limits, public education cam-paigns, and the reduction of mortalityfrom specific causes such as flood-con-trol structures and hoop nets are all posi-tive steps. However, the loss of at least37 manatees in the spring of 1982 fromred tide show how tenuous any progresscan be.

In the near future, many of the man-made sources of warm water that mana-tees have come to depend on will beapproaching the end of their operatinglife span. Decisions will have to be madeas to how to compensate or cope withthese losses.26 The struggle to protectthe manatee will have to continue formany years.

As the human population of Florida con-tinues to grow, the competition betweenman and manatee for the use of aquatichabitats will increase. If manatees are tosurvive, ways must be found to minimizethis conflict and sufficient waterfrontproperty must be left undeveloped. Atsome point we must realize that if the hu-

man population of the state is allowed togrow indefinitely, there will be very littlewildlife and few wild places left.

Non-legislative solutions are very im-portant. These include public education,environmental and conservation organi-zations, corporate funding, and land-useplanning that considers the needs of ma-natees.89 Attention also must be directedat cooperative efforts with other nationsto develop research and conservationplans for manatee populations outside ofthe United States. Much still needs to bedone if future generations are to knowthese unique animals.

Acknowledgements

The following specialists areacknowledged for their review of a draftof this manuscript: Dr. Daryl P. Dom-ning, Howard University; Mr. Patrick M.Rose, Florida Department of Natural Re-sources; and Dr. Thomas J. O'Shea, U.S.Fish and Wildlife Service.

Florida Power & Light Company (FPL),in its concern for the environment, hasfunded a series of educational booklets,including this one, as well as many othereducational and research projects. Dr J.Ross Wilcox, chief ecologist with the en-vironmental affairs department at FPL, isresponsible for developing and coordina-ting these projects.

Additional Information Available fromFPL

Publications

Florida's Sea Turtles Florida's Wood Storks Florida's Alligators and



Crocodiles The Florida Panther

16-mm Films

Silent Sirens: Manatees in Peril (a 25-minute film about manatees in Florida)Seasons in the Swamp (a 28-minute filmabout wildlife and seasonal cycles of asouth Florida cypress swamp) These ma-terials may be obtained by writing to:Florida Power & Light Company Corpo-rate Communications P.O. Box 029100Miami, Florida 33102-9100

Manatee Protection Zones in Florida

The numbers refer to counties that aretargeted by the Department of NaturalResources for protection zones. Areas inthe following counties have boating spe-ed limits already in effect or planned:

1.Citrus County 2.Sarasota County3.Lee County 4.Collier County5.Dade County 6.Broward County7.Palm Beach County 8.MartinCounty 9.St. Lucie County 10.. In-dian River County 11.. BrevardCounty 12.. Volusia County 13..Duval County

For site-specific details, consult the localmarine patrol in the appropriate county.

Blue indicates general distribution of theWest Indian manatee in the Caribbean.

Boating Speed Zones

To alert the boater and protect the mana-tee, the law provides a number of cautio-nary and regulatory speed zones. Fo-llowing are some illustrations and a brief

explanation of the various signs:

Safe Operation Zone A sign indicatingthat you may resume safe boating speed;visible as you leave a protected area.

Caution Zone A zone frequently inhabi-ted by manatees, requiring caution on thepart of boaters to avoid disturbing or in-juring the animals.

Slow Speed Zone A no-wake or minimum-wake zone whereboats must not be on a plane and must belevel in the water; generally these signsare posted on the fringe of protectedareas to warn you that you are approa-ching an area frequented by manatees; insome areas the channel is exempt.

Idle Speed Zone A zone inwhich boats are not permitted to go anyfaster than necessary to be steered; gene-rally these signs appear near the center ofa protected manatee zone.

No Entry Zone A protec-ted zone that prohibits boating,swimming and diving for the protectionof manatees. For information on obtai-ning "Caution, Manatee Area" and dis-play signs for your area and boat ramps,please contact the Bureau of ProtectedSpecies Management at 904-922-4330.

Help Save the Manatee

You can help save the manatee. You canmake a donation of $1 or more to the De-partment of Natural Resources to helpprotect the manatee. When filing your

boat registration, simply note the amountyou would like to contribute in the boxmarked "manatee donation."

When renewing or purchasing new autotags, request a "manatee tag." The addi-tional fee you'll pay will fund manateeresearch and conservation activities at thestate and federal levels, in addition to en-vironmental education in Florida schools.Call your local auto tag agency for addi-tional information.

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34.. Irvine, A.B. and H.W. Campbell.1978. Aerial census of the West Indianmanatee, Trichechus manatus, in thesoutheastern United States. Journal ofMammalogy 59(3):613-617.

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38.. Rathbun, G.B. and J.R. Reid. 1985.Cataloging West Indian Manatees in Flo-rida. Abstract No. 0512. Session W03.Abstracts of papers and posters. FourthInternational Theriological Congress. Ed-monton, Canada.

39.. McClenaghan, L.R. and T.J. O'Shea.(in press) Genetic variability in the Flori-da manatee (Trichechus manatus). Jour-nal of Mammalogy.

40.. Kinnard, M.F. 1985. Aerial census ofmanatees in northeastern Florida. Biolo-gical Conservation 32:59-79.

41.. Packard, J.M. 1983. Proposed re-search/management plan for Crystal Ri-ver manatees. Volume 1. Summary. Te-chnical Report No. 7. Florida Cooperati-



ve Fish and Wildlife Research Unit, Uni-versity of Florida, Gainesville, Florida.31 pp.

42.. Reynolds, J.E. and J.R. Wilcox.1986. Distribution and abundance of theWest Indian manatee Trichechus manatusaround selected Florida power plants fo-llowing winter cold fronts: 1984-1985.Biological Conservation 38:103-113.

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46.. Bertram, C.K.R. and G.C.L. Ber-tram. 1968. The Sirenia as aquatic meat-producing herbivores. Symposium of theZoological Society of London 21:385-391.

47.. Allsopp, W.H.L. 1960. The manatee.Ecology and use for weed control. Nature188 (4752):762.

48.. Sguros, P. 1966. Research report andextension proposal submitted to the Cen-tral and Southern Florida Flood ControlBoard on the use of the Florida manateeas an agent for the suppression of aquaticand bank weed growth in essential inlandwaterways Department of BiologicalSciences, Florida Atlantic University. 57pp.

49.. Etheridge, K., G.B. Rathbun, J.A.Powell and I.J. Kochman. 1985. Con-sumption of aquatic plants by the WestIndian manatee Journal of Aquatic PlantManagement 23:21-25.

50.. Haller, W.T. and J.V. Shireman.1982. Vegetation and herbicide monito-ring study in Kings Bay, Crystal River,Florida. Project Report, U.S. Army Corpsof Engineers Contract No. DAC W17-80-6-0062. Jacksonville, Florida. (cited inEtheridge et al. 1985; reference number49)

51.. Odell, D.K., D.J. Forrester and E.D.Asper. 1982. A preliminary analysis oforgan weights and sexual maturity in theWest Indian manatee (Trichecus mana-tus). Pages 52-65 in R.L. Brownell andK. Ralls (eds.). The West Indian manateein Florida Proceedings of a workshopheld in Orlando, Florida, 27- 29 March1978. Florida Department of Natural Re-sources. 154 pp.

52.. Asper, E.D. 1979. Commitment tomanatee health, research: Sea World'srole. Florida Conservation News15(2):14-17.

53.. Scholander, P.F. and L. Irving. 1941.Experimental investigations of the respi-ration and diving of the Florida manatee.Journal of Cellular and ComparativePhysiology 17(2):169-191.

54.. Hartman, D.S. 1979. Ecology andBehavior of the Manatee (Trichechusmanatus) in Florida. The American So-ciety of Mammalogists, Special Publica-tion No. 5. 153 pp.

55.. Bachman, K.C. and A.B. Irvine.

1979. Composition of milk from the Flo-rida manatee, Trichechus manatus lati-rostris Comparative Biochemistry andPhysiology 62A:873-878.

56.. Domning, D.P. and L.C. Hayek.1984. Horizontal tooth replacement in theAmazonian manatee (Trichechus inun-guis) Mammalia 48(1): 105-127.

57.. O'Shea, T.J. and S.H. Shane. 1985.Female-offspring behavior in West In-dian manatees. Abstract No. 0407. Ses-sion W03 Abstracts of papers and pos-ters. Fourth International TheriologicalCongress, Edmonton, Canada.

58.. Powell, J.A. 1981. The manatee po-pulation in Crystal River, Citrus County,Florida. Pages 33-40 in R.L. Brownelland K. Ralls (eds.). The West Indian Ma-natee in Florida. Proceedings of aworkshop held in Orlando, Florida, 27-29 March 1978. Florida Department ofNatural Resources. 154 pp.

59.. Bertram, G.C.L. and C.K.R. Ber-tram. 1964 Manatees in the Guianas.Zoologica 49(6):115-120.

60.. Bengtson, J.L. 1983. Estimating foodconsumption of free-ranging manatees inFlorida. Journal of Wildlife Management47(4):1186-1192.

61.. Best, R.C. 1981. Foods and feedinghabits of wild and captive Sirenia.Mammal Review 11(1):3-29.

62.. Lefebvre, L.W. and R.K. Frohlich.1986. Movements of radio-tagged mana-tees in southwest Florida, January 1985-March 1986 Unpublished interim report.U.S. Fish and Wildlife Service and Flori-da Department of Natural Resources. 86

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63.. Scott, M.D. and J.A. Powell. 1982.Commensal feeding of little blue heronswith manatees. Wilson Bulletin94(2):215-216.

64.. Domning, D.P. 1980. Feeding posi-tion preference in manatees (Trichechus).Journal of Mammalogy 61(3):544-547.

65.. O'Shea, T.J. 1986. Mast foraging byWest Indian manatees (Trichechus mana-tus). Journal of Mammalogy 67(1):183-185.

66.. Powell J.A. 1978. Evidence of carni-vory in manatees (Trichechus manatus).Journal of Mammalogy 59(2):442.

67.. Rathbun, G.B. and T.J. O'Shesa.1984. The manatee's simple social life:scent marking in an aquatic mammal. Pa-ges 300-301 in D. Macdonald (ed.). TheEncyclopedia of Mammals. Facts on FilePublications, New York. 944 pp.

68.. Bullock, T.H., T.J. O'Shea and M.C.McClune. 1982. Auditory evoked poten-tials in the West Indian manatee (Sirenia:Trichechus manatus). Journal of Compa-rative Physiology 148:547-544.

69.. Schevill, W.E. and W.A. Watkins.1965. Underwater calls of Trichechus(manatee). Nature 205(4969):373-374.

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71.. Bengtson, J.L. and S.M. Fitzgerald.1985. Potential role of vocalizations in



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72.. Cohen, J.L., G.S. Tucker and D.K.Odell. 1982. The photoreceptors of theWest Indian manatee. Journal of Mor-phology 173:197-202.

73.. Moore, J.C. 1956. Observations ofmanatees in aggregations. American Mu-seum Novitates 1811:1-24.

74.. Rose, P.M. and S.P. McCutcheon.1980. Manatees (Trichechus manatus):abundance and distribution in and aroundseveral Florida power plant effluents.Prepared for Florida Power & LightCompany. Contract No. 31534-86626.Florida Audubon Society. 128 pp.

75.. Irvine, A.B. 1983. Manatee metabo-lism and its influence on distribution inFlorida. Biological Conservation 25:315-334.

76.. Brownell, R.L. 1980 West IndianManatee Recovery Plan. Prepared by theU.S. Fish and Wildlife Service in coope-ration with the West Indian Manatee Re-covery Team. 35 pp.

77.. Beck, C.A., R.K. Bonde and G.B.Rathbun. 1982. Analyses of propellerwounds on manatees in Florida. Journalof Wildlife Management 46(2):531- 535.

78.. Reid, J.P. and G.B. Rathbun. 1986.1985 manatee identification catalogupdate. Unpublished interim report, Flo-rida Power & Light Company. 14 pp.

79.. O'Shea, T.J., C.A. Beck, R.K. Bon-de, H.I. Kochman and D.K. Odell. 1985.An analysis of manatee mortality patternsin Florida, 1976-81. Journal of WildlifeManagement 49(1):1-11.

80.. Odell, D.K. and J.E. Reynolds. 1979.Observations on manatee mortality insouth Florida. Journal of Wildlife Mana-gement 43:572-577.

81.. Forrester, D.J., F.H. White, J.C.Woodard and N.P. Thompson. 1975. In-tussusception in a Florida manatee. Jour-nal of Wildlife Diseases 11:566- 568.

82.. Beusse, D.O., E.D. Asper and S.W.Searles. 1981. Diagnosis and treatment ofmanatees at Sea World of Florida. Pages111-120 in R.L. Brownell and K. Ralls(eds.). The West Indian Manatee in Flori-

da. Proceedings of a workshop held inOrlando, Florida, 27-29 March 1978.Florida Department of Natural Resour-ces. 154 pp.

83.. O'Shea, T.J., J.F. Moore and H.I.Kochman. 1984. Contaminant concentra-tions in manatees in Florida. Journal ofWildlife Management 48(3):741-748.

84.. Buergelt, C.D., R.K. Bonde, C.A.Beck, T.J. O'Shea. 1984 Pathologic fin-dings in manatees in Florida. Journal ofthe American Veterinary Medical Asso-ciation 185(11):1331-1334.

85.. Campbell, H.W. and A.B. Irvine.1981. Manatee mortality during the unu-sually cold winter of 1976-1977. Pages86-91 in R.L. Brownell and K. Ralls(eds.). The West Indian Manatee in Flori-da. Proceedings of a workshop held inOrlando, Florida, 27-29 March 1978.Florida Department of Natural Resour-ces. 154 pp.

86.. O'Shea, T.J. 1986. Update on satelli-te telemetry efforts with Florida mana-tees. Sirenews 6:4-6.

87.. Ray, C.E. and D.P. Domning. 1986.Manatees and genocide. Marine MammalScience 2(1):77-79.

88.. Domning, D.P. 1986. Review of ma-natees: gentle giants in peril. Sirenews6:11-12.

89.. Packard, J.M. and P.M. Rose. 1985.Strategies for protection of non- exploi-ted sirenian populations. Abstract No.0479. Session W03. Abstracts of papersand posters. Fourth International Therio-logical Congress, Edmonton, Canada.

(Quotations from this booklet of 250words or less are permitted when accom-panied by a credit line reading "Reprin-ted from The West Indian Manatee inFlorida, Copyright 1989, Florida Power& Light Company." Brief excerpts, suchas selected sentences, may be identifiedby a reference to the booklet and FPL.)

Department of Environmental ProtectionBureau of Protected Species Manage-ment 3900 Commonwealth BoulevardTallahassee, FL 32399-3000

Last updated: March 31, 1999


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