The name pinnipeds or fin-footed (Latin: pinnipedia) comes from the Latin words pinna (fin or flipper) and pedis (foot). Pinnipeds is the umbrella name for those species living in (salted) water of which the limbs modicated to flippers. Pinnipeds have 4 flippers: 2 front-flippers and 2 hind-flippers.
Pinnipeds are marine mammals. They have 5 characteristics in common with other mammalians: they have hair, they breathe air, they give live birth (no eggs), nurse their young and are warm-blooded (which means that hhey have a high constant body temperature independent of their surrounding). Because pinnipeds live in marine environments and find their food at sea. They are called marine mammals. In contrast to other marine mammals, like whales and dolphins, pinnipeds are adapted to both land and sea.
33 species of pinnipeds which can be divided into three groups:
Both the True Seals and the Eared Seals have some subfamilies. Ringed Seals are a subfamily of the True Seals whereas Fur Seals is a subfamily of the Eared Seals. The Walrus has a very odd miscellany of characteristics of both True Seals and Eared Seals. The family of walruses has only two species. It is the smallest family of pinnipeds.
In contrast to whales and dolphins pinnipeds spend their time partly in the water and partly on land or ice. Pinnipeds go ashore to rest, to breed, to give birth to their pups and to haul out. Approximately two third of their life pinnipeds spent in the water.
Following their predecessors, - early varieties of bears and otters that lived in the oceans millions of years ago -, pinnipeds perfectly adapted to their cold environment. They have a thick layer of fat right under their skin that insulates their body. This layer is called blubber. A pinnipeds' blubber not only insulates the body, it also stores a lot of energy. Due to this blubber pinnipeds are very streamlined, which causes low resistance and safes a lot of energy while swimming. Their aerodynamic shape allows them to hunt their quarries in an amazing fast and efficient way.
Pinnipeds have a high volume of red corpuscles and a high concentration of haemoglobin in their blood. Besides they have more blood than other mammals. Pinnipeds have three times the blood volume of a person having the same weight. Because of their high blood volume, the large amount of red corpuscles and the high concentration of haemoglobin they can take more oxygen in their bodies. This allow them to stay under the water surface over two hours and to dive very deep.
The variety of species of pinnipeds all over the world eat a wide range of different kinds of food: prawn, crustacean, molluscs, fish, inkfish and penguins. Some species even eat birds.
Pinnipeds have some natural enemies. Their main enemies are orcas, some species of sharks, polar bears and humans. Since human beings became aware of the (commercial) value of the seal fur, blubber and meat seal hunting started and it still goes on. Pollution of the oceans, the extreme fishing by humans, derelicts on the bottoms of the oceans (in which the animals get entangled) and disruption and violation of their environment are even bigger dangers for pinnipeds. Some species extinct in the 20st century, many others are still threatened with extinction and therefore are protected animals.
© May 2003, Suzanne M. van den Bercken.
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