MAMALIA AIR

Water Mammal yaitu mamalia yang hidup di laut maupun di air tawar. Contoh hewan ini adalah Sea

Lions, The Walrus, Sperm Whale, Beluga Whale, Blue Whale, Manatees, Narwhal, The Platypus,

Dolphins, Dugong, Elephant Seal, Northern Fur Seal, Gray seal, Leopard Seal,Sea Otters.

Ciri-ciri mamalia

a. Mempunyai kelenjar susu yang terletak disisi bawah tubuh (di ketiak). Betina dapat

mengeluarkan susu setelah melahirkan. Kelenjar ini seperti kelenjar keringat, jadi diatur oleh

hormon. Air susu marine mammal mengandung 40-50% lemak untuk mensupport pertumbuhan

bayinta agar memiliki lapisan lemak yang cukup.

b. Melahirkan (viviparous), menyusui.

Dugong with attached remora (Lamen Island, Epi, Vanuatu).

c. Bulu, sedikitnya ada dalam satu siklus hidup. Bulu ikan paus hanya beberapa helai di sekitar

tenggorokan dan hilang setelah dewasa. Bulu tumbuh dari kantong bulu di dalam kulit yang

dilengkapi dengan kelenjar palit yang mengeluarkan minyak sehingga nampak mengkilat. Bulu

berperan sebagai termoregulasi (pengatur suhu / memper -tahankan suhu tubuh pada tingkat

tertentu.

d. Jantung terdiri dari 4 bilik

e. Eritrocit tanpa inti dan bi concaf

f. Otak relatif besar

g. Pada rongga dada terdapat iga dan diaphragma.

h. Marine mammal bernafas dari udara sedangkan hewan laut bernafas dari udara yang terlarut di

air.

i. Suhu tubuh relatif lebih tinggi dari suhu lingkungannya, karena dibantu oleh lapisan lemak dan

bulu di tubuhnya.

j. Mempunyai kemampuan melawan arus (countercurrent exchange) seperti gerakan hauling

(menggulung) untuk mengurangi penurunan panas tubuh.

Marine Mammal/ Mamalia laut

Adalah mamalia yang hidup di laut atau mencari makannya di laut. Merupakan evolusi dari nenek

moyang nya yang hidup di daratan kemudian beradaptasi hidup di air. Umumnya besar-besar

(charismatic megafauna), bentuk tubuhnya hydrodynamis, ekstremitas nya termodifikasi untuk

bergerak di air dan mengalami adaptasi untuk berbagai suhu (termoregulasi) karena beberapa

species dapat beradaptasi untuk berbagai tingkat suhu karena memiliki lapisan lemak yang tebal (tick

layer blubber) untuk mencegah hilangnya panas tubuh.

Hewan laut yang beradaptasi penuh hidup di air adalah ordo Cetacea dan Sirenia yang

seluruh siklus hidupnya di dalam air. Sedangkan ordo lainnya memanfaatkan sebagian waktunya di

daratan. Beruang kutub sebagian besar hidupnya dimanfaatkan di laut meskipun lautnya beku.

sangat pandai berenang di laut terbuka dalam satu hari dapat mencapai 74 km, sehingga beruang

kutub oleh ilmuwan digolongkan dalam marine mammal.

Beberapa jenis mamalia ini menuju kepunahan, bahkan banyak yang saat ini sudah punah.

karena dulunya di eksploitasi untuk diambil lemak, daging, taring dan bulunya. Sehingga saat ini

banyak dilindungi. Mamalia air tedapatasi untuk berenang memanfaatkan sirip-nya untuk bergerak.

Ikan juga berenang menggunakan sirip-2nya. Ikan umumnya mempunyai sirip caudal yang tegak

sedangkan marine mamalia mempunyai sirip caudal yang horisontal.

Kelompok marine mamalia

Diperkirakan terdapat 120 species yang dikelompokkan menjadi 3 ordo.

1. Sirenia / sirenians : Famili Trichechidae : manatee (3 species)

Famili Dugongidae / dugong (1 species)

2. Cetacea (, dolphins dan Lumba-lumba / porpoises)

Sub ordo Mysticeti : Baleen whales/ Paus ( 14 atau 15 species)

Sub ordo Odontoceti : Toothed whales (± 73 species)

3. Carnivora

Super famili : Pinnipedia (berasal dari nenek moyang ber gigi taring)

Famili Phocidae : true seals / anjing laut (± 20 species)

Famili Otariidae : eared seals (± 16 species)

Famili Odobenidae : walrus (1 species)

Famili Mustelidae : sea otter (Enhydra lutris)

Marine otter (Lontra felina)

Famili Ursidae : Polar bear (beruang kutub) Ursus maritimus

Sea Lions

The Walrus

Platypus

The platypus lives in small streams and rivers over a large area of eastern Australia. The map above shows this with dark purple. It has been seen in alpine lakes in Tasmania in the south, and north in Queensland as far as the Cape York Peninsula in tropical rain forest rivers.[3]

In the past, platypuses lived in South Australia but they no longer live there. There are platypus on Kangaroo Island, but these were brought to the island in an attempt to save animals people thought might become extinct.[5] There are very few if any platypuses left in most the Murray-Darling Basin.[6] The water there is no good because people used it to grow plants, and cleared the trees from the land. It is strange that the platypus does not live in some healthy rivers. It does live in some less healthy coastal rivers, for example the Maribyrnong River in Victoria.

Platypus are difficult to see in the wild. They dislike areas with people, spend most of their time underground or under water, and sleep during the day. At Eungella National Park in Queensland, there are spots on the river with viewing areas where wild platypus can usually be seen each evening.[4]

Platypus

Reproduksi nya bertelur The eggs develop in utero for about 28 days with only about 10 days of external incubation (in contrast to a chicken egg, which spends about 1 day in tract and 21 days externally).[34] After laying her eggs in its nest, the female curls around them. The incubation period is separated into three parts. In the first, the embryo has no functional organs and relies on the yolk sac for sustenance. The yolk is absorbed by the developing young.[44] During the second, the digits develop, and in the last, the egg tooth appears.[45]

When the babies come out of the eggs after about ten days, they hold on to the mother. The mother makes milk for the new babies. The platypus does not have nipples or teats (puting susu), but milk comes through small openings in the skin( milk is released through pores in the skin). There are grooves on her abdomen that form pools of milk, allowing the young to lap it up (memudahkan anaknya untuk meminum susu tsb). The young platypus drinks the milk from the mother's skin while she lies on her back. At six weeks the babies have fur and are able to leave the burrow for short trips , the offspring are suckled (menyusu) for three to four months. After four months they no longer need their mother's milk.[3]

During incubation and weaning, the mother initially only leaves the burrow for short periods to forage (cari makan). When doing so, she creates a number of thin soil plugs along the length of burrow possibly to protect the young from predators; pushing past these on her return forces water from her fur and allows the burrow to remain dry.[46] After about five weeks, the mother begins to spend more time away from her young and at around four months the young emerge (muncul) from the burrow.[33] A platypus is born with teeth, but these drop out at a very early age, leaving the horny plates they grind their food with.[47]

The fossil is thought to be about 110 million years old, which means that the Platypus-like animal was alive during the Cretaceous period, making it the oldest mammal fossil found in Australia. Monotrematum sudamericanum, another fossil relative of the Platypus, has been found in Argentina, indicating that monotremes were present in the supercontinent of Gondwana when the continents of South America and Australia were joined via Antarctica (up to about 167 million years ago).[16][51]

When on land, the platypus lives in a short, straight, oval holes, like a rabbit burrows. These holes are between 3 m (10 ft) and 8 m (26 ft) long. It makes these holes in the riverbank a little above the water. It likes them hidden under roots. When a female platypus is pregnant (ready to have babies), the female makes much larger holes, up to 20 m (66 ft) long. She blocks the tunnel with earth at several places. At the end of the tunnel, she builds a nest out of reeds (river grass) for her eggs.[4]

Europeans saw the first platypus in the 18th century. They sent the skin of a dead platypus to Britain, so scientists could study it. At first, the scientists thought the skin was a joke, because they thought no animal could look so strange. They thought an Asian had made it from pieces of different animals.

National Geographic magazine had a story on the platypus in 1939. Many people all over the world had never heard of the platypus. The story told how hard it is to raise

platypus babies in zoos. (Raising is helping little babies to grow.) Even today, humans have raised only few platypuses. David Fleay at the Healesville Sanctuary in Victoria had the first successful zoo raised platypus in 1946. He nearly did it again in 1972 at the David Fleay Wildlife Park at Burleigh Heads, Queensland, but it died at 50 days.[7] Healesville raised another in 1998 and again in 2000. Taronga Zoo in Sydney bred twins in 2003, and had another birth in 2006.[8]

The platypus will probably not die out completely in the near future. Ecologists say that it is secure but faces future threat (safe now but not in the future) or common but vulnerable (there are a lot now but they are not safe). They say this because people can make the water unsafe for the platypus.

DolphinFor other uses, see Dolphin (disambiguation)

.

Bottlenose Dolphinbreaching in the bow wave of a boat

Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's Dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 LT; 11 ST) (the Orca or Killer Whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating fish and squid. The family Delphinidae is the largest in the Cetacea, and relatively recent: dolphins evolved about ten million years ago, during the Miocene. Dolphins are considered to be amongst the most intelligent of animals and their often friendly appearance and seemingly playful attitude have made them popular in human culture.

Common Dolphin

Spotted Dolphin

Commerson's Dolphin

Dusky Dolphin

Killer Whales, a lso known as Orcas

Origin of the name

The name is originally from Ancient Greek δελφίς (delphís; "dolphin"), which was related to the Greek δελφύς (delphys; "womb"). The animal's name can therefore be interpreted as meaning "a 'fish' with a womb".[1] The name was transmitted via the Latin delphinus, Middle Latin dolfinus and the Old French daulphin, which reintroduced the ph into the word.

The word is used in a few different ways. It can mean:

Any member of the family Delphinidae (oceanic dolphins), Any member of the families Delphinidae and Platanistoidea (oceanic

and river dolphins), Any member of the suborder Odontoceti (toothed whales; these

include the above families and some others), Used casually as a synonym for Bottlenose Dolphin, the most

common and familiar species of dolphin.

In this article, the second definition is used. Porpoises (suborder Odontoceti, family Phocoenidae) are thus not dolphins in this sense. Orcas and some closely related species belong to the Delphinidae family and therefore qualify as dolphins, even though they are called whales in common language. A group of dolphins can be called a "school" or a "pod". Male dolphins are called "bulls", females "cows" and young dolphins are called "calves".[2]

The Boto, or Amazon River Dolphin Suborder Odontoceti, toothed whales

o Family Delphinidae, oceanic dolphins Genus Delphinus

Long-Beaked Common Dolphin , Delphinus capensis Short-Beaked Common Dolphin , Delphinus delphis

Genus Tursiops Common Bottlenose Dolphin , Tursiops truncatus Indo-Pacific Bottlenose Dolphin , Tursiops aduncus

Genus Lissodelphis Northern Rightwhale Dolphin , Lissodelphis borealis Southern Rightwhale Dolphin , Lissiodelphis peronii

Genus Sotalia Tucuxi , Sotalia fluviatilis Costero , Sotalia guianensis

Genus Sousa Indo-Pacific Hump-backed Dolphin , Sousa chinensis

Chinese White Dolphin (the Chinese variant), Sousa chinensis chinensis

Atlantic Humpbacked Dolphin , Sousa teuszii Genus Stenella

Atlantic Spotted Dolphin , Stenella frontalis Clymene Dolphin , Stenella clymene Pantropical Spotted Dolphin , Stenella attenuata

Spinner Dolphin , Stenella longirostris Striped Dolphin , Stenella coeruleoalba

Genus Steno Rough-Toothed Dolphin , Steno bredanensis

Genus Cephalorynchus Chilean Dolphin , Cephalorhynchus eutropia Commerson's Dolphin , Cephalorhynchus commersonii Heaviside's Dolphin , Cephalorhynchus heavisidii Hector's Dolphin , Cephalorhynchus hectori

Genus Grampus Risso's Dolphin , Grampus griseus

Genus Lagenodelphis Fraser's Dolphin , Lagenodelphis hosei

Genus Lagenorhyncus Atlantic White-Sided Dolphin , Lagenorhynchus acutus Dusky Dolphin , Lagenorhynchus obscurus Hourglass Dolphin , Lagenorhynchus cruciger Pacific White-Sided Dolphin , Lagenorhynchus obliquidens Peale's Dolphin , Lagenorhynchus australis White-Beaked Dolphin , Lagenorhynchus albirostris

Genus Orcaella Australian Snubfin Dolphin , Orcaella heinsohni Irrawaddy Dolphin , Orcaella brevirostris

Genus Peponocephala Melon-headed Whale , Peponocephala electra

Genus Orcinus Killer Whale (Orca), Orcinus orca

Genus Feresa Pygmy Killer Whale , Feresa attenuata

Genus Pseudorca False Killer Whale , Pseudorca crassidens

Genus Globicephala Long-finned Pilot Whale , Globicephala melas Short-finned Pilot Whale , Globicephala macrorhynchus

Genus †Australodelphis †Australodelphis mirus

o Superfamily Platanistoidea Family Platanistidae

Ganges and Indus River Dolphin , Platanista gangetica with two subspecies

Ganges River Dolphin (or Susu), Platanista gangetica gangetica

Indus River Dolphin (or Bhulan), Platanista gangetica minor Family Iniidae

Amazon River Dolphin (or Boto), Inia geoffrensis Family Lipotidae

Chinese River Dolphin (or Baiji), Lipotes vexillifer (possibly extinct, since December 2006)

Family Pontoporiidae La Plata Dolphin (or Franciscana), Pontoporia blainvillei

Six species in the family Delphinidae are commonly called "whales" but are strictly speaking dolphins. They are sometimes called blackfish.

Melon-headed Whale , Peponocephala electra Killer Whale (Orca), Orcinus orca Pygmy Killer Whale , Feresa attenuata

Wolphin Kawili'Kai at the Sea Life Park in Hawaii.

False Killer Whale, Psudorca crassidens Long-finned Pilot Whale, Globicephala melas Short-finned Pilot Whale, Globicephala macrorhynchus

Hybrid dolphins

In 1933, three strange dolphins were beached off the Irish coast; these appeared to be hybrids between Risso's Dolphin and the Bottlenose Dolphin.[3] This mating has since been repeated in captivity and a hybrid calf was born. In captivity, a Bottlenose Dolphin and a Rough-toothed Dolphin produced hybrid offspring.[4] A Common-Bottlenose hybrid lives at SeaWorld California [5] Various other dolphin hybrids live in captivity around the world or have been reported in the wild, such as a Bottlenose-Atlantic Spotted hybrid.[6] The best known hybrid however is the Wolphin, a False Killer Whale-Bottlenose Dolphin hybrid. The Wolphin is a fertile hybrid, and two such Wolphins currently live at the Sea Life Park in Hawaii, the first having been born in 1985 from a male False Killer Whale and a female Bottlenose. Wolphins have also been observed in the wild.[7]

Dugong Not to be confused with Dewgong or Dougong

Fossil range: Early Eocene–Recent

Conservation status Binomial name

Vulnerable (mudah diserang) (IUCN 3.1)[2] Dugong dugon (Müller, 1776)

Scientific classification Natural range of D. dugon.

Kingdom: Animalia Subfamily: DugonginaeSimpson, 1932

Phylum: Chordata

Class: Mammalia Genus: DugongLacépède, 1799

Order: Sirenia Species: D. dugon

Family: DugongidaeGray, 1821

Beruang Kutub

Whale

Sperm Whale

Sperm whales are sociable animals that live in groups. The group structure varies according to the

age and sex of the whale. Males live apart from females. The females form groups together with their

young, numbering from five to 30 animals. There are also smaller bachelor pods of young, non-

breeding whales, as well as much larger groups, consisting of many females, young, and a dominant,

sexually mature bull. The whales, dive, swim, feed, and sleep together within their group. They also

have a language of sonar clicks which they use to communicate. In summer, the whales migrate to

feed in the Arctic and Antarctic.

The sperm whale has been ruthlessly hunted by man for centuries, and continues to be persecuted.

Whalers have taken advantage of the whale's protective instinct, whereby all members of a group will

surround an injured animal in what is known as the Marguerite formation. Whalers harpoon a single

sperm whale to attract other whales who come to its rescue and then kill them as well. Man hunts the

sperm whale for food, and for the oil its blubber provides. It is also hunted for the spermaceti wax

found in its head and for a substance called ambergris, found in its intestines.

Groups of sperm whales begin their migration to the equator from the Arctic and Antarctic every fall for

the winter breeding season. The bulls attempt to form groups of up to 30 adult females. Fierce fights

between males for females are not uncommon. Once the group is established, the bull mates with any

female not already pregnant or with young. After mating, the female gives birth 14-16 months later.

The other females protect her while she is giving birth, and then help the calf to the surface to take its

first breath. The mother feeds her calf with fat-rich milk for as long as two years, by which time it has

grown to a length of about 23 feet.

The sperm whale feeds on bottom-dwelling organisms, such as squid. Sometimes, giant squid put up

such a struggle that scars are made on the whale's head by its tentacles. Scientists are not certain

how the sperm whale catches its prey, but it is believed that the whale stuns it with very loud sound

waves. The sperm whale will also eat snapper, lobster, and even shark. It swallows its prey whole. An

adult whale will eat up to 1 ton of food every day.

Sperm whales live in the oceans of the world in two groups--one migrates north of the equator to the

Arctic and the other south of the equator to the Antarctic. Despite protection from the International

Whaling Commission, numbers have dropped from 170,000 males and slightly fewer females to only

71,000 males and 125,000 females.

Beluga Whale

The beluga is a vocal whale; it makes a lot of different sounds from bird-sounding chirps to mighty roars. Like all whales, the beluga whale uses these sounds to communicate with each other.. It also has a all kinds of facial expression; these, too, may be also used for communication. The beluga whale once roamed the oceans in herds of ten-thousands. Too much hunting by humans hunting has reduced its numbers. Now large herds of beluga whales gather only when returning to the shallow waters where they live. Each herd is divided into smaller groups, or pods, of breeding or bachelor males and females with young. Pods spread out in the places where they feed but join up again for the yearly migration to the places where they breed. The beluga hunts in small groups, eating worms, crustaceans, and fish that live in schools or on the seabed. Working in small groups of five or six, the whales herd their prey into shallow waters, or toward the shore. The beluga whale "talks" to other whales in the hunting group. The beluga's teeth, which appear when the mammal is about two to three years old, are not used for feeding, since the beluga whale swallows its prey whole. All the same, they wear down, probably because the beluga whale rubs them together to make sounds--another way to communicate. Unlike other kinds of whales, the beluga has a very flexible neck and is able to move its head from side to side. This flexibility allows the beluga whale a wide sweep of the ocean floor when hunting for prey. Its flippers are very flexible too; they enable it to move very easily in all kinds of tight situations, even backwards if it is necessary. Mating occurs from April to June. The dominant male mates with more than one female. After the mating season, the beluga whale migrates south to warmer coastal waters and arrives in June to July. A female, pregnant from last year's mating, will split into a small nursing pod. She gives birth to one single calf, who arrives tail first, underwater, and then swims to the surface of the water to breathe. The newborn calf is grayish brown and turns a lighter gray after a couple of years. It does not turn white until it becomes an adult. After about a month, when the calf is strong enough, all the beluga whales migrate back to the colder Arctic waters. The young beluga suckles from its mother for about two years. The beluga whale was easy prey for whalers of the nineteenth century. Whalers forced the belugas onto beaches, stranding them. Thousands of whales died this way. The beluga is no longer killed for its meat in Western waters, since it contains toxic levels of poisonous marine pollution. Now, the main threats to its survival are pollution of shallow coastal waters, the building of hydroelectric dams that alter its habitat, and the widespread disturbance of its breeding grounds. It lives in the coastal waters of Arctic and sub-Arctic regions of North America, Greenland, Europe and Asia. Present population of the beluga whale is unknown but thought to be recovering from heaby causualties as a result of eighteenth and nineteenth century whaling. Modern threats include pollution and disturbance of breeding grounds.

The Manatee

The manatee, Trichechus manatus, is a grayish-brown, walrus-like animal weighing on average between 800-1200 pounds and growing approximately 12.7 feet in length. They are mammals, hence they breathe air, have body hair and nurse their young. Manatees have a round, flattened tail, and 2 front flippers. These flippers are used in steering while swimming, as well as for holding their food. While underwater, flaps close over their nostrils, to prevent water from interfering with breathing. The newborn calves range from 3 to 5 feet long, and beginning only several weeks after birth, they start eating plants such as seagrasses and algae. Manatees are completely harmless and nonaggressive and are often shy and reclusive. There are approximately 2,247 manatees remaining in the southeastern U.S. and they are concentrated in Florida year-round. During cold weather, manatees are attracted to the warm-water discharges of five FPL plants. Approximately 1200 animals have been counted with serial surveys at these facilities. The waters throughout the Caribbean, Central America, Colombia, Venezuela, and the northern coast of Brazil, as well as peninsular Florida, are home to the West Indian Manatee. Two subspecies of the West Indian Manatee exist today. One is found only in Florida and the other is located throughout the northern region of the Caribbean, and the coastal waters of North and South America. In the winter months, cold weather shortens their northernmost range to Florida, while in the summer time, some swim as far north as Virginia and as far west as Texas. In a few cases, manatees have been observed to cover over 520 miles, each way, during their migrations. One manatee was known to swim 143 miles in only four days! Manatee deaths throughout Florida have become an issue of serious concern. The primary causes of death are collisions with boats, cold weather, and red tides as well as entanglement in fishing line, loss of habitat, and chemical pollution. These ancient creatures need our help in order to survive into the next century and beyond.

The Narwhal is unlike any other cetacean. The male has a long spiralling tusk which is not normally possessed by the female. The tusk which grows to a length of 1.5-3m (5-10ft) is actually a modified tooth and looks like a twisted and gnarled walking stick. During the 17th century the Narwhal tusk was thought to have been the horn of the legendary unicorn. Studies suggest that males engage in

The Narwhal

aggressive behavior when competing for females. Scars attributed to tusk action have been found on the heads of adult males which are more likely to have broken tusks. The Narwhal shares many physical characteristics with the Beluga (Delphinapterus leucas). They are similar in shape and size, they have short beaks, rounded heads, lack dorsal fins and have a thick layer of blubber. An adult Narwhal will grow to a length of 4-5m (13-16ft) and weigh 0.8-1.6 tonnes. The head of the Narwhal is proportionately small with a bulbous forehead. While almost all males develope a single tusk from the tooth on the left-hand side of upper jaw, only 3% of females grow a thin tusk. All have a very slight beak, short flippers and flukes which appear to be on 'backwards'. The Narwhal lives mainly in the High Arctic, often amongst the pack ice and generally offshore. There are large concentrations in the Davis Strait, around Baffin Bay and in the Greenland Sea. The advance and retreat of the ice initiates migration. The Narwhal is seldom found further south than 70 deg North and spends its summer in deep, cold fjords and bays. The Narwhal has a varied diet, feeding upon squid, fish and crustaceans. With few functional teeth this animal must use suction and the emission of a jet of water to dislodge prey such as bottom-living fish and molluscs. Its highly flexible neck aids the scanning of a broad area and the capture of more moblie prey. Although the Narwhal is preyed upon by Polar Bears, Walruses, Orcas and a number of sharks its major enemy is man. It has been hunted by the Inuit people for centuries for its tusk, flesh and other edible parts. Its thick skin is traditionally eated raw as a delicacy, much of the meat is fed to sled dogs and the blubber is rendered down for heating and lighting. In the Thule district Narwhal are still traditionally harpooned from kayak but most modern Inuit hunters use fast motor boats and high-powered rifles. Subsistance hunting communities have a long tradition of established rules but they clearly need to take account of developments that alter their operation from an 'aboriginal' manner. The world total for Narwhal's stands at between 25,000 and 45,000 animals.

Elephant seal From Wikipedia, the free encyclopedia

Elephant Seal Contents

Male and female Northern Elephant Seals

[hide] 1 Appearance

2 Ecology 3 Lifespan 4 Gallery

5 See also 6 References

7 External links

Scientific classification Appearance

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Carnivora

Suborder: Pinnipedia

Family: Phocidae

Genus: Mirounga

Species

M. angustirostrisM. leonina

Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the Northern Elephant Seal (M. angustirostris) and the Southern Elephant Seal (M. leonina). Both were hunted to the brink of extinction by the end of the nineteenth century, but numbers have since recovered. The Northern Elephant Seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S., Canada and Mexico. The Southern Elephant Seal is found in the southern hemisphere on islands such as South Georgia, Macquarie Island, and on the coasts of New Zealand, South Africa, and Argentina in the Peninsula Valdés, which is the fourth largest elephant seal colony in the world.

Male Southern Elephant Seal in Kerguelen Islands

Elephant seals take their name from the large proboscis of the adult males (bulls) which resembles an elephant's trunk[1]. The bull's proboscis is used in producing extraordinarily loud roaring noises, especially during the mating season. More importantly, however, the nose acts as a sort of rebreather, filled with cavities designed to reabsorb moisture from the animals' exhalations. This is important during the mating season when the male seals rarely leave the beach to feed, and therefore must conserve body moisture, as they have no incoming source of water. Bulls of both the northern elephant seal and the southern elephant seal reach a length of 16 ft (5 m) and a weight of 6,000 lb (2,700 kg), and are much larger than the cows, which typically measure about 10 ft (3 m) and 2,000 lb (900 kg)[2]

[3]. The largest known bull elephant seal weighed 11,000 lb (5,000 kg) and measured 6.9 m (22.5 ft) in length. This makes the elephant seal the largest member of the order Carnivora.

Ecology

Male Northern Elephant Seals fighting in California

Elephant seals spend upwards to 80 percent of their lives in the ocean. They can hold their breath for over 120 minutes—longer than any other non-cetacean mammal. Elephant seals dive to 1550 m beneath the ocean's surface[4][5] (the deepest recorded dive of an Elephant Seal is 1,581m by a male in 1989[6]). The average depth of their dives is about 300 to 600 meters, typically for around 20 min for females and 60 min (1 hour) for males, as they search for their favorite foods, which are skates, rays, squid, octopuses, eels, penguin (Southerns only), and small sharks. Their stomachs also often contain gastroliths. While excellent swimmers, they are even more surprising on land, where they have a higher velocity than the average human when moving over sand dunes.

Elephant seals are shielded from extreme cold by their blubber, more so than by fur. The animals' hair and outer layers of skin molt periodically. The skin has to be re-grown by blood vessels reaching through the blubber. When molting occurs, the seal is susceptible to the cold, and must rest on land, in a safe place called a "haul-out." While the molt is taking place the bulls cease fighting with one another as there are not breeding harems and females in estrous to protect. In fact, northern males haul out in August, and females in May-June.

Elephant seals have evolved to have a very large volume of blood, allowing them to hold a large amount of oxygen for use when diving. They have large sinuses in their abdomens to hold blood and can also store oxygenated blood in their muscles with increased myoglobin concentrations in muscle. In addition they have a larger proportion of oxygen-carrying red blood cells. All these adaptions enable them to dive for periods up to two hours.[7]

[edit] Lifespan

Female elephant seals have an average life expectancy of about 23 years, and can give birth starting at the age of 4-5. Males reach maturity at five years, but generally don't achieve alpha status until the age of 8, with the prime breeding years being between ages 9 and 12. The average life expectancy of a male elephant seal is 20 years.[8] Only 1 in 10 males will become an alpha or beta male.

[edit] GalleryWikimedia Commons has media related to: Mirounga angustirostris

Elephant seals (Mirounga angustirostris) on a beach, San Simeon, California

Northern Elephant Seals during moulting season near San Simeon, California, USA