Information about Pinniped

Pinnipedia Fossil range: Late Oligocene - Recent
Common Seal (Phoca vitulina)
Scientific classification
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Mammalia Order: Carnivora Suborder: Caniformia Superfamily: Pinnipedia
Families
Odobenidae Otariidae Phocidae

Pinnipeds ("fin-feet", lit. "winged feet") are marine mammals belonging to the former biological suborder Pinnipedia (sometimes now a superfamily) of the order Carnivora. The pinnipeds now fall within the suborder Caniformia and comprise the families Odobenidae (walruses), Otariidae (eared seals, including sea lions and fur seals), and Phocidae (true seals). Recent molecular analysis reveals that the closest living relatives of the pinnipeds are the bears, which was already suspected for some time.^[1] An alternative hypothesis held that pinnipeds are polyphyletic, with the true seals derived from otterlike creatures and the walruses and eared seals from bearlike creatures, but the aforementioned molecular study established that the pinnipeds are indeed monophyletic (derived from a common ancestor).

Pinnipeds apparently evolved from a bearlike ancestor about 23 million years ago, at the transition between the warmer Paleogene period and the cooler Neogene period. First true seals and then walruses branched off, forming new families.

Morphology

Pinnipeds are typically sleek-bodied and rather large. Their bodies are well adapted to their aquatic habitat, in which they spend most of their lives. In place of hands, their forelimbs are large flippers (hence the name "featherfoot"), and their bodies narrow out into a tail. The smallest pinniped, the Galapagos fur seal, weighs about 30 kg (66 lb) when full-grown and is 1.2 m (4 ft) long; the largest, the male southern elephant seal, is over 4 m (13 ft) long and weighs up to 2,200 kg (4,850 lb, more than 2 tons).

Eared seals also called "walking seals" are made of sea lions and fur seals and communicate by "barking." They have large foreflippers compared to earless seals and use them as their main source of maneuverablity in the water. They are also more agile on land than earless seals. As their name suggests, eared seals have external ears. As a group, sea lions are larger than fur seals. Fur seals have more underfur. It has been argued that dividing fur seals and sea lions into subfamilies (Arctocephalinae and Otariinae) is unjustified, noting that Northern fur seals and Cape fur seals are more related to sea lions than other fur seals.

The Walrus is the sole member of its family. They are easily recognized by their long tusks and large bodies. They are more closely related to eared seals than to earless seals.

Earless seals, also called “true seals,” lack external ears. They have more developed hind limbs and swim by powerful sideways movements of these, yet are more cumbersome on land than the eared seals. Earless seals are better built for diving. They are more streamlined than eared seals, and can therefore swim more effectively over long distances. However, because they cannot turn their hind flippers downward, they are very clumsy on land, having to wriggle with their front flippers and abdominal muscles; this method of locomotion is called galumphing. True seals do not communicate by "barking" like eared seals. They communicate by slapping the water and grunting.

Adaptations

Flippers

Pinnipeds have shorter limbs than most other mammals. As noted above, their limbs have evolved into flippers with true seals having more developed hind flippers and eared seals having more developed fore flippers. The walrus is intermediate between the two. A pinniped’s fingers and toes are bound together by a web of skin . They also have claws are can either be in the on the front flippers (earless seals) or back flippers (eared seals). Pinnipeds can move weightlessly in the water and thus their flippers can be smaller in relation to their size than the wings of a bird or bat.

Oxygen conservation

Pinnipeds can conserve oxygen for long period of time underwater. When the animal starts diving its heart rate slows to about one-tenth of the norm. The arteries squeeze shut and the sense organs and nervous system are the only organs to continue to receive a normal flow of blood. Pinnipeds are able to resist more pain and fatigue caused by lactic acid accumulation than other mammals. However once they return to the water surface, they need time to recover and bring their body chemistry back to normal. ^[2]

Warmth

To keep warm in cold waters, pinnipeds have a layer of blubber under their skin (which also provides buoyancy). The thickness depends on the species. Their blubber can also provide food for the animal. Newborn pinnipeds have no blubber. Some pinnipeds can also can get warm from their fur. The white coat of the infant harp seal, may trap the energy of sunlight as heat near the skin. As noted above, fur seal have underfur.

Moulting

Like other mammals, pinnipeds have to shed their fur once in a while. Eared seals shed more slowly than earless seals. Most earless seals spend time in the water while moulting.

Other adaptations

A pinniped’s eyes are well adapted for seeing both above and below the water. When diving the animal has a clear membrane that covers and protects its eyes. In addition, its nostrils close automatically. Testicles and mammary glands are located in slits under the skin to keep the pinniped’s streamlined shape. They also have whiskers to help navigate and sensors in their skull to absorb sounds underwater and trasmit them to the cochlea.

Evolution

Pinnipeds appear to have diverged from their bear-like ancestors during the Latest Oligocene. The earliest fossil pinniped that has been found is Enaliarctos, which lived 24 – 22 million years ago, at the boundary between the Oligocene and Miocene periods. It is believed to have been a good swimmer, but to have been able to move on land as well as in water, more like an otter than like modern pinnipeds. DNA evidence suggests that all modern pinnipeds descend from a common ancestor that lived sometime in the earliest Miocene, possibly an Enaliarctos-like mammal. ^[3]

Feeding

All pinnipeds are carnivorous, eating fish, shellfish, squid, and other marine creatures. Most are generalist feeders, but some are specialists. For example; Ross Seals and Southern elephant seals mainly feed on squid. Crabeater seals eat mostly krill and Ringed seals feed almost exclusively on crustaceans. Additionally, the Walrus consumes molluscan prey items by sucking the soft parts from the shell.

Some seals will even eat warm-blooded prey including other seals. The leopard seal, which is probably the most carnivorous and predatory of all the pinnipeds, will eat penguins and well as Crabeater and Ross Seals. The South American sea lion also eats penguin as well as flying seabirds and young South American fur seals. Steller sea lions have been recorded eating Northern fur seal pups, Common seal pups and birds.

Reproduction

Pinnipeds often come ashore or haul out on ice to breed, often travelling long distances from their feeding grounds to suitable mating grounds with a high level of reproductive synchrony. Almost all pinnipeds are polygynous, i.e. males breed with up to several dozen females in a season. Males of many species, (e.g. elephant seals and Northern fur seals) aggressively defend groups of specific females, referred to as harems. Males of other species (e.g. most sea lions) defend territories on reproductive rookeries while females move freely between them. Some form of competition, either for females or territories, some of which can be violent, is an integral part of the male breeding strategy among most pinnipeds. Otariids, which are generally more land-adapted, tend to form major aggregations in the summer months on beaches or rocky outcrops. Consequently, their reproductive behavior is easier to observe and well studied. Walruses and many phocids, on the other hand, tend to form smaller aggregations, often in remote locations or on ice, and copulate in the water. Their reproductive behavior is therefore generally less well known.

Females have a postpartum oestrus allowing them to mate soon after giving birth. Subsequent implantation of the embryo is delayed (embryonic diapause) thus removing the need to come ashore (haul-out) twice, once to give birth and again later to mate. After giving birth mothers suckle their young for a variable length of time. Amongst the phocids, lactation varies from 4 to 50 days, whereas the otarids may lactate from 4 to 36 months. This reflects the fact that phocid feeding grounds tend to be a long way off-shore so lactation is associated with maternal fasting. To compensate for the short lactation period, the fat content of phocid milk is higher than in any other species of marine mammal (45 – 60% fat). After lactation most female phocids make extensive migratory movements to feeding grounds for intensive foraging to recoup depleted energy reserves. On the other hand, otarid feeding grounds are generally closer to shore and females go on foraging trips to maintain lactation. Fat content of otarid milk is lower than that of the phocids owing to the protracted lactatory period (typically 25 – 50%). Protracted nursing also leads to the formation of social bonds.

Taxonomy

• Family: Odobenidae
• Walrus, Odobenus rosmarus
• Imagotaria downsi (extinct)
• Family Otariidae
• Northern Fur Seal, Callorhinus ursinus
• Antarctic Fur Seal, Arctocephalus gazella
• Guadalupe Fur Seal, Arctocephalus townsendi
• Juan Fernandez Fur Seal, Arctocephalus philippii
• Galapagos Fur Seal, Arctocephalus galapagoensis
• Cape Fur Seal, Arctocephalus pusillus
• New Zealand Fur Seal or Southern Fur Seal, Arctocephalus forsteri
• Subantarctic Fur Seal, Arctocephalus tropicalis
• South American Fur Seal, Arctocephalus australis
• Steller's Sea Lion, Eumetopias jubatus
• California Sea Lion, Zalophus californianus
• Japanese Sea Lion, Zalophus (californianus) japonicus - extinct (1950s)
• South American Sea Lion, Otaria flavescens
• Australian Sea Lion, Neophoca cinerea
• New Zealand Sea Lion, Phocarctos hookeri
• Family Phocidae
• Subfamily Monachinae
• Tribe Monachini
• Monachopsis (extinct)
• Pristiphoca (extinct)
• Properiptychus (extinct)
• Messiphoca (extinct)
• Mesotaria (extinct)
• Callophoca (extinct)
• Pliophoca (extinct)
• Pontophoca (extinct)
• Hawaiian Monk Seal, Monachus schauinslandi
• Mediterranean Monk Seal, Monachus monachus
• Caribbean Monk Seal, Monachus tropicalis (probably extinct around 1950)
• Tribe Miroungini
• Northern Elephant Seal, Mirounga angustirostris
• Southern Elephant Seal, Mirounga leonina
• Tribe Lobodontini
• Monotherium wymani (extinct)
• Ross Seal, Ommatophoca rossi
• Crabeater Seal, Lobodon carcinophagus
• Leopard Seal, Hydrurga leptonyx
• Weddell Seal, Leptonychotes weddellii
• Swan-necked Seal, Acrophoca longirostris (extinct)
• Piscophoca pacifica (extinct)
• Homiphoca capensis (extinct)
• Subfamily Phocinae
• Kawas benegasorum (extinct)
• Leptophoca lenis (extinct)
• Preapusa (extinct)
• Cryptophoca (extinct)
• Bearded Seal, Erignathus barbatus
• Hooded Seal, Cystophora cristata
• Tribe Phocini
• Common Seal or Harbor Seal, Phoca vitulina
• Spotted Seal or Larga Seal, Phoca largha
• Ringed Seal, Pusa hispida (formerly Phoca hispida)
• Nerpa or Baikal Seal, Pusa sibirica (formerly Phoca sibirica)
• Caspian Seal, Pusa caspica (formerly Phoca caspica)
• Harp Seal, Pagophilus groenlandica (formerly Phoca groenlandicus)
• Ribbon Seal, Histriophoca fasciata (formerly Phoca fasciata)
• Phocanella (extinct)
• Platyphoca (extinct)
• Gryphoca (extinct)
• Grey Seal, Halichoerus grypus

In culture

Seals and sea lions are popular animals in the media. They are often portrayed balancing beach balls on their noses and clapping with their flippers.

Notable fictional seals include:

• Lou Seal: mascot for the San Francisco Giants
• Kotick: the main character in Rudyard Kipling's short story The White Seal, later made into a cartoon by Chuck Jones
• Salty a seal that appears in the Disney cartoons Pluto's Playmate and Mickey and the Seal and later in Mickey's Mouseworks and House of Mouse.
• The title character of Andre
• Slappy the sea lion from Slappy and the Stinkers
• Whiskers from Manta and Moray
• Esmeralda the sea lion from the Disney version of 20,000 Leagues Under the Sea
• The San-X company characters Mamegoma
• The main characters of

See also

• Cetaceans
• Sirenians
• Seal (disambiguation)
• Nothosaur

References