Sea lions

An unusual sighting of a female hooker's sea lion on Macquarie Island
An unusual sighting of a female hooker's sea lion on Macquarie Island (Photo: Clair Holland)
juvenile Hooker's sea lion (left) and elephant sealOur 'resident' young Hooker's sea lion is a young sea lion sitting among the vehicle tracksHooker's sea lion asleep with elephant seals on Macquarie Island

Scientific name: Phocarctos hookeri

Hooker’s sea lions, also known as New Zealand sea lions, are one of only five species of sea lions in the world, the others being the Australian sea lion, the South American sea lion, the California sea lion and Steller sea lion.

Physical description and related species

Adult male sea lions can weigh over 400 kg and will aggressively defend harems of up to about 25 females from other males during the breeding season. Females weigh 85–160 kg and pups weigh  7–8 kg at birth.

Distribution and abundance

A rare species, Hooker’s sea lions are one of the most regionally localised, breeding almost exclusively in New Zealand's sub-Antarctic Auckland Islands. A few sea lions also breed on New Zealand’s Campbell Island.

Female Hooker’s sea lions tend to stay reasonably close to their breeding locations, but males range further afield. Each year, some male sea lions are seen on Macquarie Island, the only Australian territory within their range.

With their small, localised population Hooker's sea lions are considered to be endangered. Although management measures have been introduced to mitigate the impact of fisheries, a decline in their numbers has continued.

Conservation status: endangered

Breeding

Pups are born in December and January each summer and are suckled for up to 10 months.

Diet and feeding

Hooker’s sea lions feed on, or near, the seabed on a wide variety of prey including octopus, squid and several types of fish. They will occasionally feed on pelagic schooling crustaceans like lobster krill, and even on sea birds and fur seals. Large males have been seen killing and eating young southern elephant seals at the Campbell Islands.

Hooker’s sea lions can dive deeper and longer than any other of the world's fur seals or sea lions. Although most feeding is done in waters of 100–200 m, with each dive lasting 3–6 minutes, some sea lions have been recorded to dive to over 600 m with dives of over 12 minutes.

The diving performance of this species is at the limit of their physical ability. They achieve such amazing depths by swimming fast in the first part of the dive and then by gliding down to the seabed, keeping very still to conserve energy and oxygen.