The two subspecies look alike in the field and their subspecific status is based mainly on their different geographic distributions. The two subspecies are the largest of the fur seals. The adult males are dark grey or brown on the back and lighter on the belly. The mane becomes lighter with age. Females are brownish-grey on the back and light brown on the belly and chest.
Adults are paler on the muzzle, lower jaw and on the face.
Females reach sexual maturity at 3-6 years. Males probably do not mate until 9-12 years. Pups are born black but moult to a greyish-fawn colour with a pale throat. Pups are nursed for a year or longer. Peak pupping occurs in the first week of December although pups are born from late October to early January.