pinniped

Pinnipeds are a widely distributed group of fin-footed marine mammals that includes seals, sea lions, and walruses. They form the clade Pinnipedia within the order Carnivora and are adapted to a semi-aquatic lifestyle, spending much of their lives in the ocean but returning to land or ice to breed, molt, and rest.

Pinnipeds are divided into three families: Phocidae (true seals), Otariidae (eared seals, including sea lions and fur seals), and Odobenidae (walruses). True seals lack external ear flaps and move on land mainly by wriggling on their bellies, using their hind limbs. Otariids have external ear flaps and can “walk” on land by rotating their hind flippers forward under their bodies. Walruses are distinguished by their long tusks, which are enlarged incisor teeth used for defense, dominance displays, and foraging on the seafloor.

Adaptations common to pinnipeds include a streamlined body, thick insulating blubber, and dense fur in some species. They have sensitive vibrissae (whiskers) for detecting prey underwater, specialized lungs and blood chemistry for deep and prolonged dives, and efficient thermoregulation to cope with cold aquatic environments. Their limbs are modified into flippers that enhance swimming, while some species come ashore on beaches or ice to molt and breed.

Pinnipeds primarily feed on fish, squid, and crustaceans, with foraging patterns ranging from solitary to highly social. Reproduction varies by lineage; females typically give birth to one pup after a lengthy gestation and lactate to prepare the young for independent life. Many species form seasonal breeding colonies, and some undertake long migrations.

Conservation status among pinnipeds ranges from common to endangered, with threats including habitat loss, climate change, bycatch, and hunting.