They are the most lion like of all the sea lions with a massive neck, broad head and upturned muzzle. Females average 200 cm and weigh 150 kg. Males are dark brown to brownish orange, and darken with age. Their manes and undersides may be lighter and their faces may be darker. The female sea lions and subadults are yellow to brownish orange and the colour may be patterned and have different hues or tints.
Pups are black above and greyish orange below.
They moult to dark brown at about 4 weeks of age. Females reach sexual maturity at about 4 years and males one or two years later. Peak pupping occurs in January although births occur from September to March depending on location. Pups are nursed by their mothers for 6-12 months. No obvious migra tion occurs within this species.