Pinnipeds: Seals and Sea Lions
Seals, Sea lions and Walrus are currently placed in a Sub-order, the Pinnipedia, of the Order Carnivora which also includes the bears, dogs, raccoons, weasels (including otters), hyenas, cats, and mongooses. There have many recent studies on the genetic and fossil history of these groups and their place in the scheme of mammalian classification may well change in the near future.
Three families of living pinnipeds are recognized, the Phocidae (hair seals or true seals), the Otaridae (fur seals and sea lions) and the Odobenidae (walrus). The term pinnipedia translates from Latin as "fin foot." All of these animals must come ashore to breed, give birth and nurse their young, though some species are at sea for several months at a time while others return to the shore every day.
Phocid seals include elephant seals, several species of ice seals (some are found in fresh water lakes) and the harbor seal of temperate coastlines. The monk seals are found in the Mediterranean Sea and Hawaii. Four phocid species inhabit the Antarctic ice pack. All of these seals have a vertical undulating motion when they move on land. The pelvic architecture does not provide a stable anchor point for the rear flippers to engage the ground for propulsion and the rear flippers are directed rearward.
The Otarids, fur seals and sea lions, are found in temperate colder waters and are associated in tropical latitudes with cold water upwelling currents. They have external ear flaps. The arm pit or axilla encloses the forelimbs to about the level of the forearm. In all the pinnipeds the hind limb e.g. rear legs are enclosed to the level of the ankle. Sea lions and fur seals can rotate their hind feet forward and therefore use the pelvic architecture in propelling themselves forward with considerable speed.
The walruses, Odobenidae, are found in recent times in Arctic ice pack areas, both Pacific and Atlantic but in colonial times were found as far south as Sable Island off Nova Scotia. They are very similar to the Otarids in locomotion. Under the Marine Mammal Protection Act walruses are within the jurisdiction of the U.S. Fish and Wildlife Service.
The National Marine Fisheries Service (NMFS) has jurisdiction over four species of pinnipeds in the U.S. that are protected under the Endangered Species Act (ESA). These include the Caribbean monk seal, the Guadalupe fur seal, the Hawaiian monk seal and the Steller sea lion. The Caribbean monk seal and the Hawaiian monk seal are listed as endangered while the Guadalupe fur seal and Steller sea lion are currently listed as threatened. In addition, NMFS has jurisdiction over the North Pacific fur seal, which has been designated as depleted under the Marine Mammal Protection Act (MMPA).
Commercial hunting of seals in the 18th and 19th century, and in the early years of this century played a large role in pinniped population declines. Other factors involved have been coastal development and competition with man for prey species.
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