Seals are cousins of weasels, raccoons and red pandas
Seals, sea lions and walruses look like a world apart from land carnivores, yet their nearest living relatives are the musteloids: weasels, raccoons, skunks and red pandas. The two lines split around 50 million years ago. Molecular evidence also settled an old debate, showing that all pinnipeds descend from one common ancestor.
The group holds 34 living species in three families: the walrus on its own, the eared seals such as sea lions and fur seals, and the earless or true seals. More than 50 extinct species are known from fossils. The German naturalist Johann Illiger first recognised them as a distinct group in 1811, and the name means fin-footed, from Latin pinna and pes. Sizes vary enormously, from the Baikal seal at about a metre and 45 kilograms to the southern elephant seal, 5 metres long and up to 3,200 kilograms.
The families move differently. Eared seals swim mainly with their front flippers and can tuck their hind flippers under the body to walk on land, as walruses can. True seals and walruses drive themselves through water with their hind limbs, and true seals are clumsy ashore. Eared seals have visible ear flaps; the others do not. All have eyes and ears tuned to both air and water, sensitive whiskers, and a layer of blubber, and every species except the walrus is furred. Slower than dolphins, they are more flexible and agile.
Most prefer cold waters and spend the bulk of their lives at sea, coming ashore to breed, give birth, moult or escape sharks and orcas. Fish and marine invertebrates are staple foods, walruses specialise in bottom-dwelling molluscs, and leopard seals take penguins and other seals. Males usually mate with several females. Mothers do nearly all the parenting; walruses even nurse at sea. The soundscape is rich, ranging from the barking of California sea lions to walrus calls that ring like a gong and the elaborate songs Weddell seals produce.
Commercial hunting once pursued seals relentlessly, and international law now protects them. Even so, the Japanese sea lion and Caribbean monk seal vanished in the past century, and the Mediterranean and Hawaiian monk seals are endangered.
Source: Pinniped
