There are 33 species of pinnipeds alive today, most of which are known as seals. Pinnipedia is made up of three main groups: The walrus, which is the only living member of the family Odobenidae; the eared seals of Otariidae, including numerous kinds of fur seal and sea lion; and the earless seals, known as true seals or Phocidae. Despite the name, earless seals have ears—they’re just hidden beneath the surface of their skin.

Pinnipeds can be found on every continent on Earth, though most species occur in cold-water environments. Thick layers of fat, also known as blubber, keep the animals warm, in addition to dense fur. Walruses are the exception to the rule, as these large, tusked