elephant seal, also called sea elephant, either of the two largest pinnipeds (aquatic mammals of the suborder Pinnipedia): the northern elephant seal (species Mirounga angustirostris), now found mainly on coastal islands off California and Baja California; or the southern elephant seal (M. leonina), found throughout sub-Antarctic regions. Elephant seals are gregarious animals named for their size and for the male’s inflatable, trunklike snout. They are in the family Phocidae.
The northern elephant seal is yellowish or gray-brown, and the southern is blue-gray. The southern species has an extensive molting period in which considerable patches of hair and skin are shed. Males of both species attain a length of approximately 6.5 metres (21 feet) and a weight of about 3,530 kg (7,780 pounds) and are much larger than the females, which grow to 3.5 metres and weigh 900 kg. Elephant seals feed on fish and on squid or other cephalopods. The northern species is nonmigratory; the southern elephant seal, like the northern form, breeds and molts on land, but it winters at sea, possibly near the pack ice. During the breeding season, elephant seals become aggressive toward each other. The bulls fight to establish territories along beaches and to acquire harems of up to 40 cows. The cows produce single brownish black pups yearly. They mate about three weeks after delivery, and a three-month dormancy period ensues before the fertilized ovum implants. The total pregnancy lasts about 11 months. Both species have been hunted for their oil and in the 19th century were reduced almost to extinction; under protection, however, they have gradually increased in number and their survival is no longer threatened.