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空間分佈 (spatial distribution)
─ 動物行為學 (Ethology)
鄭先祐 (Ayo)
國立 臺南大學 環境與生態學院生態科學與技術學系 教授
Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/
大學部 生態學與保育生物學學程 ( 必選 ) 2010 年 秋冬
Ayo 教材 (動物行為學 2010) 2
10 空間分佈 (Spatial distribution)
Remaining at home versus leaving Habitat selection ( 棲地選擇 ) Migration ( 遷徙 )
Ayo 教材 (動物行為學 2010) 3
Introduction to animal movement
Nearly all of the 25 species of sturgeons ( 鱘魚 ) are endangered
Chinese sturgeon can reach 4 or 5 m in length, weigh more than 550 kg (1,000 lbs.), and live for a century It is anadromous, spending most of its life in the sea But returning to freshwater to breed
Anadromous 由海移棲淡水河產卵的
Ayo 教材 (動物行為學 2010) 4
Humans have disrupted sturgeon spawning
Historically, Chinese sturgeon spawned upstream in the Yangtze River Taking 18 months to migrate 3,000 km to their
spawning grounds The Gezhouba Dam blocked Chinese sturgeon from
their migration route They bred below the dam
The number of spawning adults plummeted Disruption by the dam, water pollution, overfishing,
and heavy boat traffic
Ayo 教材 (動物行為學 2010) 5
Dispersal and philopatry
Natal dispersal: movement between the natal area or social group and the area or social group where breeding takes place Animals are born in one place and move to another to
breed They don’t return to their birthplace
Breeding (post-breeding) dispersal: movement between two successive breeding areas or social groups Occurs after reproduction
Natal philopatry: offspring remain at their natal area and share the home range or territory with their parents
Ayo 教材 (動物行為學 2010) 6
Costs of natal philopatry
Inbreeding: mating between relatives Parents and offspring or between siblings Inbreeding reduces variation among offspring
It is hard to determine the fitness costs of inbreeding Because the frequency of inbreeding is usually low
Mexican jays have fitness costs associated with inbreeding Smaller brood sizes, suggesting hatching failure Fewer of the inbred nestlings survived to the next year
Mexican jay
Ayo 教材 (動物行為學 2010) 7
Other costs of natal philopatry
Reproductive suppression: adult breeders suppress reproductive development of young through chemical means (e.g., pheromones) or behavioral methods (e.g., aggression) Suppressed young may not reproduce Their genes are represented by helping rear other young
Young compete with relatives for food, nest sites, or mates
Ayo 教材 (動物行為學 2010) 8
Benefits associated with philopatry
Populations become adapted to local conditions Genes that work well under local conditions are
favored by selection An animal that disperses may not be as well adapted to
its new home Familiarity with the local physical and social setting
Young are efficient at finding and controlling food and escaping from predators
Reduced levels of aggression and stress associated with social interactions
Ayo 教材 (動物行為學 2010) 9
Another benefit of philopatry
Philopatric young may live longer and leave more offspring Because of the low risks and energy use associated with
living in familiar surroundings Offspring may remain at home due to constraints
A shortage of potential mates A lack of suitable territories to settle in
Ayo 教材 (動物行為學 2010) 10
Costs of natal dispersal
Dispersers face high energy costs and increased predation risk Small mammals in underground burrows have a
constant physical environment and safety from predators (hawks and owls)
Long-distance above-ground dispersal exposes them to harsh weather conditions and predators
Other costs: a lack of familiarity with the terrain High levels of aggression from residents in the new
area
Ayo 教材 (動物行為學 2010) 11
Animals in new homes face challenges
Male prairie voles released at unfamiliar locations move greater distances And take longer to find refuge than those released at
familiar locations In woodland voles and Norway rats, nonresidents
face harsh treatment by residents Dispersal-induced mortality can exceed 50% But dispersal costs can be negligible in some species
Ayo 教材 (動物行為學 2010) 12
Benefits of natal dispersal: avoiding competition
Dispersers avoid competition with kin for critical resources
Wolf spider mothers help their offspring disperse Young climb onto their mother’s abdomen Spiderlings face kin competition if they all left their
mother’s abdomen in the same location They do not simultaneously disperse from mom’s
abdomen
Ayo 教材 (動物行為學 2010) 13
Patterns of natal dispersal and maternal movement in wolk spiders ensure that siblings do not compete with one another.
Ayo 教材 (動物行為學 2010) 14
Not all species avoid competition through dispersal
In other species, avoiding competition with kin cannot explain patterns of natal dispersal
If competition for resources leads to dispersal, dispersal would increase with increases in litter size In brown bears and prairie voles natal dispersal is not
associated with litter size Natal dispersal is more common in small groups of
prairie voles Avoidance of competition for resources at home is not an
important function of natal dispersal in this species
Ayo 教材 (動物行為學 2010) 15
Benefits of natal dispersal: avoiding inbreeding
Some young leave home to avoid breeding with close relatives Young disperse in the presence of an opposite-sex
parent All members of one sex may disperse, no matter what
the ecological or social conditions In Belding’s ground squirrels, all males leave home
Regardless of the competition for mates or resources Nearly all male brown bears leave home regardless of
ecological factors (i.e. population density and sex ratio)
Ayo 教材 (動物行為學 2010) 16
Inbreeding may or may not be important
Some scientists argue that it plays a significant role in dispersal Others argue that animals rely on mate choice rather than a
risky behavior like dispersal to avoid inbreeding Young female mammals avoid selecting their brothers as
mates In response, their brothers disperse from the natal site to
find females willing to mate with them So, individuals do not disperse from home to avoid
breeding with relatives Instead, natal dispersal is the result of females not choosing
male relatives as mates
Ayo 教材 (動物行為學 2010) 17
↑Belding’s ground squirrels
← brown bears
spotted hyenas →
Ayo 教材 (動物行為學 2010) 18
Female mate choice can drive natal dispersal
Female spotted hyenas rarely disperse from the natal clan. Most, but not all, males leave their natal clan
Four hypotheses examine natal dispersal by males 1) competition with other males for mates 2) breeding with close female relatives 3) competition for food resources 4) males disperse in response to patterns of mate
choice by females Competition for mates, inbreeding avoidance, and
competition for food do not cause natal dispersal by males
Ayo 教材 (動物行為學 2010) 19
Female avoid mating with close relatives
Female hyenas follow this rule: “Avoid mating with males that were members of your
clan when you were born and select as mates those males that arrived in your clan (through birth or immigration) after your birth”
Reducing the chances that females mate with their father and older brothers
Ayo 教材 (動物行為學 2010) 20
Another aspect of female choice
Young females select males with short residency times in their clan
Males begin their reproductive career in the clan (natal or otherwise) that had the most young females Females choose them as mates Resulting in long-term fitness benefits for the males
Ayo 教材 (動物行為學 2010) 21
Proximate causes of natal dispersal
Ultimate causes of natal dispersal: avoidance of inbreeding and competition with kin for resources or mates
Proximate causes also trigger natal dispersal Sufficient body size or fat reserves, aggression from
other group members, shortage of food, attraction to opposite sex individuals in other groups, and weaken social bonds with members of the natal group
Androgens may organize dispersal behavior through organizational effects of steroid hormones
Ayo 教材 (動物行為學 2010) 22
Natal dispersal is also linked to personality ( 個性 ) Such as “boldness”( 大膽的 ) or exploratory
behavior Female great tit post-fledging movement distances
correlates with exploratory behavior This positive correlation does not characterize all
species In flying squirrels, long distance dispersers explore
less than short distance dispersers
Ayo 教材 (動物行為學 2010) 23
Sex biases in natal dispersal
Males and females differ in whether or not they disperse from their birthplace In most bird species, females are more likely to disperse In mammals, males are more likely to disperse than
females Hypotheses to explain sex-biased dispersal
(1) inbreeding avoidance (2) local resource competition (3) local mate competition (4) cooperative behavior among kin
Ayo 教材 (動物行為學 2010) 24
Sex bias in dispersal is a compromise
It avoids the genetic costs of inbreeding While enjoying the benefits of familiarity with local
physical and social conditions (philopatry) But, which sex leaves home and why is the direction of
the bias different in birds and mammals? Two explanations suggest the direction of sex bias
The sex most involved in territory acquisition and defense stays home because it benefits most from familiarity with the natal territory
The sex that gets first choice of breeding sites remains in the natal area and the other sex disperses
Ayo 教材 (動物行為學 2010) 25
Male birds are philopatric
Most birds are monogamous (they live in male-female pairs)
A resource-defense mating system: males compete for territories that attract females, rather than competing for females directly Familiarity with an area is more important to males than
to females so males should be philopatric Female birds disperse to avoid the genetic costs of
inbreeding And to choose territories with the best resources
Ayo 教材 (動物行為學 2010) 26
Female mammals are philopatric
Many mammals show mate-defense polygyny: a single male mammal defends a group of females Males compete for females rather than territories Young or subordinate males disperse to increase their
chances of mating Female mammals often live in matrilineal social groups
(groups of mothers, daughters, and granddaughters) The benefits of living with kin are high
Females benefit most by staying home Males disperse to avoid the genetic costs of inbreeding
Ayo 教材 (動物行為學 2010) 27
Sex-based dispersal
Female-biased dispersal in birds is linked to resource-defense mating systems
Male-biased dispersal in mammals is linked to mate-defense mating systems Some mammals display resource-defense (rather than
mate defense) polygyny Natal dispersal is female biased, as predicted
i.e. for sac-winged bats But, in European roe deer, dispersal is not female
biased
Ayo 教材 (動物行為學 2010) 28
Sac-winged bat ( 鞘尾蝠科 )
European roe deer
Ayo 教材 (動物行為學 2010) 29
The sex with the breeding site remains in the natal area
This model assumes that philopatry is more desirable than dispersal
Mating systems affect dispersal patterns of mammals indirectly by influencing whether the father will be present when his daughters are old enough to breed If he is not, females have first choice of the breeding
site, and they choose to stay at home If the father is still around when his daughters reach
sexual maturity, he has first choice of the breeding site, and so females disperse to avoid inbreeding
Ayo 教材 (動物行為學 2010) 30
A male mammal’s parental role is limited
Female mammals nurse their young Males have little involvement in offspring care
So, males can avoid long-term pair bonds They can wander over large areas
With intense competition over mates (i.e. elephant seals, red deer) a male’s opportunity to breed may be limited He leaves before his daughters are old enough to reproduce
So, daughters don’t have to disperse to avoid inbreeding If a male’s reproductive life span is long and he is present
when his daughters are old enough to breed (i.e. chimpanzees) Females usually disperse
Ayo 教材 (動物行為學 2010) 31
Another hypothesis for dispersal: local mate competition
Competition for mates is intense in polygynous male mammals Dispersal should be more common in males
In monogamous species, competition for mates is more equal Males and females should disperse in similar proportions
Reducing competition for mates can’t explain all sex differences in natal dispersal Avoiding inbreeding influences natal dispersal i.e. females disperse in monogamous bird species
Ayo 教材 (動物行為學 2010) 32
Kin cooperation hypothesis
Cooperative behavior contributes to sex biases in dispersal If kin exhibit cooperative behavior, it is beneficial to stay
home If cooperation benefits one sex more than the other
The cooperative sex is philopatric The other sex disperses to avoid inbreeding
The magnitude of sex-biased dispersal increases with increases in social complexity Dramatic sex differences in natal dispersal characterize
highly social polygynous mammals
Ayo 教材 (動物行為學 2010) 33
Sex bias in natal dispersal and social complexity
There is a relationship between sex-biased dispersal and social complexity
In polygynous ground-dwelling sciurids (ground squirrels, marmots, prairie dogs) Social structures range from solitary to large social
groups Male-biased natal dispersal increased with social
complexity Not from expected decreases in female dispersal
Ayo 教材 (動物行為學 2010) 34
ground squirrels
marmots
prairie dogs ( 土撥鼠 )
Ayo 教材 (動物行為學 2010) 35
In polygynous ground-dwelling sciurids (members of the squirrel family), the degree of sex bias in natal dispersal increases with social complexity.
Ayo 教材 (動物行為學 2010) 36
Understanding natal dispersal: implications for conservation
Dispersal affects the genetic structure of populations It promotes gene flow within and between populations And maintains genetic diversity
Habitat destruction fragments populations and hinders dispersal Areas between habitat fragments are inhospitable
To conserve threatened populations Preserve dispersal corridors( 廊道 ) to connect larger
areas and promote gene flow
Ayo 教材 (動物行為學 2010) 37
Stop and think
Natal dispersal and philopatry are measured by mark and recapture methods Genetic methods examine how dispersal translates into
gene flow What are some potential problems in using mark-
recapture methods to study dispersal? How could you know if an animal dispersed or died? How could you design a study to minimize this issue?
Ayo 教材 (動物行為學 2010) 38
Mark-recapture methods are often used to monitor natural populations of small mammals.
Ayo 教材 (動物行為學 2010) 39
Habitat selection
Animals that disperse from their natal site or breeding site must select a new location in which to settle
The process of habitat selection has three phases: (1) search (animal searches for a new habitat) (2) settlement (animal arrives in a new habitat and
begins to establish a home range or territory) (3) residency (animal lives in the new habitat)
The phases of search and settlement are costly The benefits of habitat selection accrue during
residency
Ayo 教材 (動物行為學 2010) 40
Indicators of habitat quality
Animals have clear habitat preferences Forest buffalos of Africa prefers grassy clearings and
open stands of forest with large trees Even though clearings are rare Herd members can maintain visual and physical contact
When selecting a habitat, animals evaluate The presence of resources (e.g., food, nest and rest sites) The presence of conspecifics, and heterospecifics
(members of another species)
Ayo 教材 (動物行為學 2010) 41
Its native habitat is the equatorial forest found in central and western Africa, and its diet consists primarily of grasses, twigs, and young shoots. African Forest Buffalo are sought after by hunters for their meat and horns. In the wild, leopards are its primary predator.
The African Forest Buffalo (Syncerus caffer nanus) is usually weighing 265–565 kilograms (580–1,250 lb), they are reddish brown in color.
Ayo 教材 (動物行為學 2010) 42
How do animals evaluate real estate?
Young lizards searching for feeding territories spend only hours evaluating a location Do not conduct a detailed assessment of prey availability They assess habitat characteristics (i.e. light intensity
and amount of leaf litter) that correlate with prey availability
A disperser evaluates the presence or absence of conspecifics in the vicinity of a prospective home By settling in an unoccupied site, it avoids intraspecific
competiton
Ayo 教材 (動物行為學 2010) 43
Fitness correlates with numbers of conspecifics
The ideal free distribution: individual fitness declines as the number of conspecifics increases
The Allee effect: individual fitness increases with number of conspecifics at low to moderate densities Having a few neighbors is beneficial Enhanced detection of predators or access to mates
Two explanations for conspecific attraction regarding habitat selection 1) Allee effect 2) conspecifics indicate habitat quality
Ayo 教材 (動物行為學 2010) 44
Conspecifics indicate habitat quality
Juvenile lizards use conspecfic presence as an indirect cue to habitat quality
Individuals evaluate characteristics of resident conspecifics Breeding birds monitor the reproductive success of
conspecifics in their local area And use this information to decide where to nest during future
breeding efforts Public information: information concerning local
conspecifics Personal information: the bird’s own breeding success also
affects whether it remains at that site or leaves
Ayo 教材 (動物行為學 2010) 45
The presence of heterospecifics has costs and benefits
For an animal considering whether to settle in an area Interactions between species that share mutual resources
could be negative due to interspecific competition Interactions between heterospecific individuals can be
beneficial Mixed species flocks of birds experience the benefits of
enhanced food acquisition and antipredator behavior The heterospecific attraction hypothesis: individuals
choose habitat patches based on the presence of established residents of another species
Ayo 教材 (動物行為學 2010) 46
The heterospecific attraction hypothesis
Predicts that individuals searching for a new home display the strongest attraction to heterospecifics When the benefits of social aggregation outweigh the
costs of competition, and When the costs of independent sampling of habitats
(evaluating habitat quality on one’s own rather than using the presence of heterospecifics as a cue) are high
Ayo 教材 (動物行為學 2010) 47
Testing the heterospecific attraction hypothesis
Several possible explanations exist for the attraction of migrant birds of one species to resident birds of other species First, residents indicate high quality habitat Second, migrants may experience food or safety benefits
from grouping with heterospecific residents Third, using presence of heterospecific residents to
indicate habitat quality may be a fast, accurate method of habitat assessment
Residents have all year to assess the quality of habitat patches
Ayo 教材 (動物行為學 2010) 48
Resident titmice influence pied flycatcher presence and fitness
Titmice and pied flycatchers both nest in cavities and forage for arboreal arthropods
Flycatchers are attracted to the vicinity of titmice Flycatchers arrive earlier on forest patches with more
titmice They prefer nest boxes placed near an active titmouse
← Titmice Pied flycatchers →
Ayo 教材 (動物行為學 2010) 49
The fitness effects of habitat selection
Brood sizes of flycatchers were larger in patches with more titmice Flycatchers breeding closer to titmice had larger nestlings
Interspecific competition is not the defining interaction between titmice and flycatchers
← Titmice Pied flycatchers →
Ayo 教材 (動物行為學 2010) 50
Two search tactics for selecting habitat
Comparison (best-of-N strategy): the animal visits several areas, revisits some, and chooses the highest quality area
Sequential search: the animal visits habitats and selects the best one An animal accepts or rejects
a location If rejected, it keeps searching
Both tactics can occur within a single population
Ayo 教材 (動物行為學 2010) 51
Sequential searches
Searchers do not return to areas they have already visited (except by chance) They may travel long distances before establishing residence
Decisions by dispersers are influenced by: The time available for the search, quality of available
habitats, and how often high quality habitats are encountered Dispersers may have an acceptance threshold
Which declines as the search continues (i.e., an animal may be selective at the start of the search and less selective later)
Ayo 教材 (動物行為學 2010) 52
Effects of natal experience
Experience in the natal environment influences habitat selection
Host preferences exhibited by the parasitoid wasp A parasitoid: an organism whose offspring
develop on or within a host, eventually killing the host
The host of a parasitoid is the equivalent of a habitat
Female parasitoids select hosts on (or within) which their offspring will develop
Ayo 教材 (動物行為學 2010) 53
Host preference in parasitoid wasps
Female wasps reared on fruit flies preferred fruit flies as hosts But only when allowed to gain experience attacking them
Cues from the natal host prime females to respond to these cues if encountered again When re-encountered, the cues are learned by females,
establishing host preference The natal environment (here, the natal host) influences
selection of a site for reproduction
Ayo 教材 (動物行為學 2010) 54
The natal habitat preference induction
NHPI: An animal’s experience in its natal habitat induces a preference for a post-dispersal habitat with similar qualities The search phase of habitat selection is costly in time,
energy and predation risk NHPI helps a disperser to more quickly and efficiently
recognize a suitable habitat Minimizing the costs of the search phase
A habitat similar to the one in which the disperser grew up would be of sufficient quality to settle in Because the individual has survived to leave home
Ayo 教材 (動物行為學 2010) 55
Another explanation for NHPI
Dispersers have greater fitness if they settle in a habitat similar to their natal habitat Because their particular phenotype has been shaped by
this type of habitat While living at home, individuals develop specific
methods for finding and capturing prey These methods might work best in post-dispersal habitats
similar to their natal habitat NHPI has been documented in diverse taxa
Insects, fishes, amphibians, birds, and mammals
Ayo 教材 (動物行為學 2010) 56
Habitat selection and conservation biology: translocation and captive-release programs
Conservation efforts using translocation (moving animals from one part of their natural range to another) and captive-release programs (breeding animals in captivity and then releasing them to the wild) often fail Animals travel long distances away from the release site Survivors may exhibit decreased condition and
reproduction Movement away from the release site make provisioning
and monitoring extremely difficult
Ayo 教材 (動物行為學 2010) 57
Many translocated animals travel long distances from the site of release. In cougars ( 美洲獅 ) , this is especially true for adult males.
Ayo 教材 (動物行為學 2010) 58
Making captive-release programs and translocations work
Movement from a release site suggests that the animal rejects the habitat and is searching for suitable habitat
Understanding habitat selection and natal habitat preference induction may inspire modifications to programs And help animals find the release site more acceptable Providing captive animals with stimuli and cues similar to
those at the release site May make them more inclined to stay at the release site
Placing stimuli and cues from the original habitat at the release site might reduce the disparity between the two habitats
Ayo 教材 (動物行為學 2010) 59
Habitat selection and conservation biology: ecological traps
Ecological trap ( 生態陷阱 ): a low quality habitat that animals prefer over a high quality habitat
Cooper’s hawks in Arizona select Tucson because of its plentiful nest sites and prey (pigeons and doves) Urban hawks nest earlier and have larger clutches But nestling mortality is higher in Tucson than rural areas Prey carry trichomoniasis ( 滴蟲病 ) , which kills nestling
hawks The hawks selected an inferior habitat – an ecological trap
Populations in an ecological trap move toward extinction
Ayo 教材 (動物行為學 2010) 60
Cooper's Hawk
Cooper's Hawk (Accipiter cooperii) is a medium-sized hawk native to the North American continent and found from Canada to Mexico.
As in many birds of prey, the male is smaller than the female. The birds found east of the Mississippi River tend to be larger on average than the birds found to the west.
Ayo 教材 (動物行為學 2010) 61
Migration
Migration: movement away from the home range that does not stop upon encountering the first suitable location Animals move until they respond to the presence of
resources (nest sites and food), and then they stop Migratory movements occur over greater distances than
dispersal
Ayo 教材 (動物行為學 2010) 62
Migrating caribou marching through Alaska in July. During the spring, many caribou breed in the tundra. Beginning in July, they migrate south, where food will be available through winter.
Ayo 教材 (動物行為學 2010) 63
Migration: one-way or round trip
In some species, migration involves movement away from an area and the subsequent return to that area Migration between breeding areas and over wintering,
or feeding, areas Associated with long-lived species (e.g., vertebrates)
In other species, migration is a one-way affair Migratory insects permanently abandon their site of
origin Associated with short-lived species (e.g., insects)
Ayo 教材 (動物行為學 2010) 64
Animals vary in the distance they migrate
A salamander travels less than a kilometer from its woodland home to its breeding pond
Northern elephant seals migrate twice a year from beaches in southern California to northern feeding grounds in the Aleutian Islands - 8000 kilometers each year
The arctic tern migrates 20,000 kilometers one-way, between its southern wintering area and northern breeding area
Long distance migrants insects: desert locusts and monarch butterflies have one-way migration distances of 5,000 km and 3,600 km, respectively
Ayo 教材 (動物行為學 2010) 65
desert locusts monarch salamander
elephant seals arctic tern
Ayo 教材 (動物行為學 2010) 66
Migration can take several forms
Migration can be obligate: an individual always migrates Facultative migrants migrate only if local conditions
deteriorate Differential migration: migration of individuals differs
by age or gender Small passerines (perching birds) may migrate in their first
year but remain on breeding grounds in subsequent years Female and juvenile blue tits migrate because they are less
able to compete for food on the breeding grounds when it becomes scarce during the nonbreeding period
Ayo 教材 (動物行為學 2010) 67
Costs of migration
Animals migrate because they produce more offspring this way then if they stayed put
But, migration takes a tremendous toll Less than half of the waterfowl in North America that
migrate south each fall return to their breeding grounds The mortality rate of black-throated blue warblers is
15 times higher during spring and autumn migration than during periods when individuals are not migrating
Ayo 教材 (動物行為學 2010) 68
Costs of migration: energy
Traveling long distances requires a great deal of energy Bird use 6-8 times more energy when flying than resting
Natural selection favors behaviors that reduce the risk of starvation during migration
Storing fat before the journey begins Fat provides more energy than carbohydrates or proteins Insects, fish, birds, and mammals put on fat reserves The body mass of long-distance migratory birds can double
Increasing body mass to avoid starvation must be balanced against the negative effects of a heavy fuel load while flying
Ayo 教材 (動物行為學 2010) 69
Saving energy during migration: stopovers
Some animals do not have sufficient fat stores to migrate without stopping
Small birds reduce their risk of starvation by refueling along the way They alternate flight and stopovers Spending more time in stopover than in flight
How do they know where to stop for food? They use landscape features (i.e. amount of hardwood
forests) which are positively correlated with arthropod abundance
Ayo 教材 (動物行為學 2010) 70
Fly-and-forage migration
Ospreys combine foraging and migration Individuals forage for fish in nearby bodies of water They move on in less than 12 hours
Other birds (i.e. falcons and seabirds) that fly extensively also use this strategy Birds that feed on the ground or in vegetation have longer
stopovers
Ayo 教材 (動物行為學 2010) 71
← 鶚(學名: Pandion haliaetus )或稱作魚鷹,是一種善於捕魚的猛禽。
鶚在隼形目中屬於鶚科,這個科只有一屬一種。
隼屬(學名 Falco )在生物分類學上是隼形目隼科中的一個屬,屬於小型猛禽,現存共有三十多種。→
Ayo 教材 (動物行為學 2010) 72
Costs of migration: risk of predation
Migrants experience heavy predation Predation risk has shaped timing and routing of migration
The predator landscape for migrants has two components Non-migratory predators along the route and the endpoints Migratory predators
Lions, cheetahs ( 獵豹 ) , and hyenas ( 鬣狗 ) track African ungulates( 有蹄類 ) Wolves follow North American caribou Water pythons( 蟒蛇 ) migrate seasonally to follow dusky
rats Songbirds flying south face five million raptors ( 猛禽
類 ) that are also making the trip
Ayo 教材 (動物行為學 2010) 73
Costs of migration: inclement weather ( 險惡的天氣 )
Migration occurs during the spring and fall Unstable weather drastically raises the cost of migration Severe rainstorms and snowstorms kill millions of migrating
monarch butterflies In birds, the most devastating mortality occurs when land
species encounter storms over water A sudden snowstorm in Minnesota killed 1.5 million
Lapland longspurs ( 鐵爪鵐 ) Unseasonably cold temperatures after arriving at breeding
areas or before departing from such areas kills migrants
Ayo 教材 (動物行為學 2010) 74
Costs of migration: obstacles
Birds crash into lighthouses, skyscrapers, and TV towers In a single night, seven towers in Illinois felled 3,200
birds Wind-powered turbines that generate electricity have
been erected in many locations Both on a small scale and large-scale wind farms
Ayo 教材 (動物行為學 2010) 75
Wind turbines kill migrants
Particularly for nocturnally active birds and bats Direct problems: animals collide with wind turbines Indirect problems result from changes to the landscape
(e.g., construction of roads, buildings, and electrical transmission lines)
Monitoring fatalities at wind facilities is hard Issues of searcher efficiency Removal of carcasses by scavengers before they can be
counted
Ayo 教材 (動物行為學 2010) 76
Benefits of migration: energy profit
Animals trade a less hospitable habitat for a more hospitable one Each fall, millions of monarch
butterflies migrate southward from Canada and the United States to fir forests in central Mexico
Ayo 教材 (動物行為學 2010) 77
Monarch butterflies settle in forests
The forest is cool but not freezing Freezing temperatures kill
monarchs Warmer temperatures elevate
metabolic rates and waste energy reserves
Tall trees provide branches on which the butterflies can roost Their thick, protective canopy
shields them from rain, snow, or hail
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Forests protect migrating monarchs
A dry monarch withstands colder temperatures better than one with water on its body
The forest canopy also serves as a blanket that keeps the butterflies warm
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Climate changes affect food supply
Migration permits exploitation of temporary or moving resources
Larvae of monarch butterflies feed only on milkweed ( 乳草 ) In the eastern United States, the plants grow during
spring and summer Despite the energy required for migration, energy is
saved By avoiding temperature stresses of northern winters,
species compensate for the energy spent on migration
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Benefits of migration: reproductive benefits
If there is so much food in the warmer winter habitats, why do species migrate?
There are advantages in rearing broods in the summer habitats Long days in the far north Birds can bring more food to
their offspring Species that breed farther north
have larger broods
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Areas provide conditions for breeding
Species migrate to areas that provide the necessary conditions for breeding or that offer protection from predators
Gray and humpback whales breed in warm coastal bays and lagoons which help protect the calves from predation
Seals( 海狗 ), sea lions( 海獅 ), and walrus( 海象 ) migrate to protected rookery sites
Sea turtles migrate thousands of kilometers between feeding grounds and breeding areas Isolated beaches have fewer predators
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座頭鯨
座頭鯨(學名: Megaptera novaeangliae ),又名大翅鯨、駝背鯨、巨臂鯨,屬於鬚鯨亞目的海洋哺乳動物。該物種為大型鯨魚:成年鯨身長可達 12 至 16 米之間( 40 至 50 英尺),目前最大記錄的雌性可達 18 米。體重 25 至 35 噸( 36 噸合 79,000 磅)。座頭鯨以其躍出水面姿勢、超長的前翅與複雜的叫聲而聞名。全世界各大海洋都有座頭鯨的蹤跡,是賞鯨者的最愛之一。已列入《瀕危野生動植物種國際貿易公約》目錄。
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灰鯨
灰鯨( Eschrichtius robustus ),現又稱東太平洋灰鯨,是一種每年來往攝食區和繁殖區的鯨。
在中國,分布於黃海、東海等海域,多棲息於熱帶及暖溫帶海域。
該物種的模式產地在瑞典。牠們約有 16 米長, 36 公頓重,一般可活到 50–60 歲。
灰鯨曾一度被稱為「魔鬼魚」,因為當牠們被追獵時會奮力搏鬥。
灰鯨是灰鯨屬中唯一的物種,亦是灰鯨科中唯一的物種。這種動物是最古老的物種之一,在地球上已有約 3000 萬年的歷史。在很久之前牠們一度是巨牙鯊的捕食對象(巨牙鯊現已滅絕)。
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海龜
Some green turtles migrate from their feeding ground off the coast of Brazil to Ascension island to breed on sheltered beaches, where it is safe from predators.
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Benefits of migration: reduced competition and predation
Animals returning to the temperate zone escape the intense competition found in warmer, more densely populated areas Without competition from nonmigrants in the tropics
Returning to temperate zones to breed reduces predation In the far north, breeding periods are very short
Birds nest simultaneously, reducing the likelihood of any single individual being taken by a predator
With decreased food, predator numbers are kept low Migratory species deprive parasites and microorganisms
of permanent hosts
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Migration and conservation biology
Long distance migrations, one of the most spectacular of biological phenomena, are becoming increasingly rare events
The Greater Yellowstone Ecosystem is a 19 million acre temperate ecosystem in Idaho, Wyoming, and Montana All 14 bison(北美野牛 ) migration routes have been lost And 78% of the pronghorn(叉角羚 ) and 58% of elk ( 駝鹿 )
routes are gone Causes include: increased human population and habitat loss
Fences, highways, and housing subdivisions block routes One solution: create a protected network of wildlife
migration corridors ( 遷徙廊道 )
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Summary
Natal dispersal: permanent movement away from the natal area or social group
In natal philopatry, offspring remain at their birth place Breeding dispersal: movement between two breeding areas or
social groups Costs of philopatry: inbreeding, reproductive suppression, and
competition with relatives for mates or resources Advantages of philopatry: genes are suited to local
conditions, familiarity with the local physical and social setting Dispersers face high energy costs and risks of predation,
increased movement and lack of familiarity with the environment
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Summary
Patterns of dispersal are due to: inbreeding avoidance, resource competition, mate competition, and cooperative behavior
Habitat selection involves search, settlement, and residency Habitat selection uses comparison (best of N) strategies and
sequential search strategies Migration occurs over greater distances than dispersal Costs of migration: energy expenditure, risks of predation,
unfamiliar and inhospitable terrain, and severe weather Advantages of migration: favorable energy balance, escaping
harsh temperatures, avoiding competition from reduced food, and reduced predation and parasitism