Facts about sea lion

Female Hooker's sea lion, Auckland
Islands

The New Zealand sea lion (Phocarctos hookeri - formerly known as the Hooker's sea lion) has a blunt nose and short whiskers. There is a marked difference in appearance between adult males and females. Mature males are brown to black in colour with well-developed manes reaching to the shoulders. Females are lighter in colour, predominantly creamy grey with darker pigmentation around their flippers.

• Adult females: length 1.6-2.0 m, weight 100-160 kg
• Adult males: length 2.4-3.5 m, weight 250-400 kg. 

Pups of both sexes are chocolate brown with paler areas around the head. Juvenile males can resemble adult females in colour and size.

Range

The major breeding colonies are found at the Auckland Islands where about 85% of pups are born on Dundas Island, Enderby Island and Figure of Eight Island. A small breeding colony is found at North West Bay of Campbell Island. Recently, offspring of a single female pup born in December 1993 in Otago have started to breed on the peninsula.

Haul-out sites are more widespread and extend to Macquarie Island in the south to Stewart Island and the islands of Foveaux Strait.

Sea lions favour sandy beaches as haul-out areas. On warm summer days they will flick sand over themselves to try to keep cool. Females with pups will often move well inland on islands using vegetation for shelter.

Remains found in midden sites in the North, South and Chatham Islands suggest this species was more widespread prior to European settlement.

Diet and foraging

Diet studies are limited for the New Zealand sea lion but those studies that have been carried out, combined with observational reports, indicate that they prey on a wide variety of species.

Squid have been shown to be an important dietary component for New Zealand sea lions in the sub-Antarctics but not for those in the mainland region. Other prey species include fish, some sharks and rays, octopus and various other invertebrates.

New Zealand sea lions have also been reported to occasionally prey upon fur seals, elephant seals, penguins and various sea birds.

New Zealand sea lions may travel up to 175 km from the coast to feed. Dives may be up to 600 m in depth, though most are less than 200 m and last four or five minutes.

Diving is almost continuous when at sea with females diving deeper, longer and covering a greater area and distance in a single foraging trip than any other fur seal or sea lion species.

Research indicates that New Zealand sea lions on the Auckland Islands may be operating at their physiological limits when foraging. This may have prevented population growth at this site.

Life history

Females mature as early as three years old and males are able to hold a territory at 8-9 years old. However, this is based on limited data and observations; age of sexual maturity is unknown. Life expectancy is similarly unclear but some research carried out has shown maximum ages of 23 years for males and females.

Breeding occurs over the summer months. Mature males are highly territorial and aggressive in their defence. On the Auckland Islands males occupy a beach in late November and pregnant females congregate at nearby haulouts. Several days prior to giving birth to a single pup, females move to the breeding beach.

Females form into harems of up to 25 and are attended by a single dominant bull. Challenger and bachelor bulls remain around the periphery and occasionally challenge the dominant bull.

Females give birth to a single pup every 1-2 years. Pupping begins in the first week of December and ceases by the third week in January at which time the remaining bulls disperse and the harems break-up. Pups are born on the beach but are moved by their mothers to nearby vegetation after about six weeks.

The females then spend the next year alternating between foraging trips to sea and periods on land suckling their pups. Pups form pods near the periphery of harems while their mothers are at sea.

Pups are dependent on their mothers for milk and protection for the first year of their lives. While mothers are at sea feeding, pups are alone. This is natural but they are particularly vulnerable to disturbance during these periods, so please keep your distance.

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