Adult males of E. jubatus average about 300-325 cm in length and 1,000-1,120 kg in weight; females average about 240 - 270 kg. in length with some individuals reaching 350 kg. This single species exhibits pronounced sexual dimorphism, slightly variable in color, ranging from light buff to reddish brown with the chest and abdomen a little darker. Adult males develop a massive neck and heavy, coarse mane. Females have 2-6 retractable mammae.

E. jubatus is non-migratory, but disperses widely throughout its range during the nonbreeding season. Rookeries are generally located on outlying rocky islands and coastlines, providing access to the open sea and abundant food resources. E. jubatus feeds primarily on fish of no particular commercial value, octopus, squid, bivalve mollusks, and crustaceans. Young fur seals, sea otters and ringed seals are also sometimes taken. E. jubatus can dive to depths of 200 meters, hunting mainly at night. Group feeding sometimes occurs to control the movement of schooling fish and squid.

The breeding season ends in late August and then the males move throughout the range, Californian males moving north along the coast and northern individuals moving south. Young are born from mid-May to mid-July with births peaking in mid-June. Females have one offspring weighing between 18-22 kg. and are dark brown to black. They can swim at birth, staying with the mother for 5-13 days and the mother then leaves the pup to forage for food. She then returns to the pup to suckle her young, after which she repeats the pattern of foraging trips and returning to her pup to nurse. At 10-14 days of age the pups form groups, playing and sleeping together while the mothers forage. Sexual maturity is attained at 3-8 years of age, but males rarely win breeding territory before age 10.

Populations of E. jubatus have dropped sharply in recent years and the USDI has issued an emergency classification of threatened for this species.

They can be found in the Northern Pacific coastal regions of Canada, China (vagrant populations to Jiangsu), Japan (from Hokkaido N), Russia, USA (Alaska, Washington, Oregon, California).