New zealand sea lion
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New Zealand sea lion
New Zealand sea lion. Source: Biopix: JK Overgaard
The New Zealand sea lion (Scientific name: Phocarctos hookeri) is one of 16 species of marine mammals in the family of Eared seals which include sea lions and fur seals. Together with the families of true seals and Walruses, Eared seals form the group of marine mammals known as pinnipeds.
The New Zealand sea lion is found only in New Zealand and breeds almost exclusively on New Zealand's subantarctic islands, in particular Dundas Island in the Auckland Islands where over 95% of all New Zealand sea lion are born in three close colonies. The species is considered "vulnerable" because of its restricted number and close proximity of breeding sites.
Eared seals differ from the true seals in having small external earflaps and hind flippers that can be turned to face forwards. Together with strong front flippers, this gives them extra mobility on land and an adult fur seal can move extremely fast across the beach if it has to. They also use their front flippers for swimming, whereas true seals use their hind flippers.
 New Zealand sea lion. Source: Roger Kirkwood/WoRMS/Encyclopedia of Life |
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Conservation Status  |
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Scientific Classification Kingdom: Anamalia (Animals) |
| Common Names Auckland sea lion Hooker's sea lion Hooker's sealion New Zealand sealion New zealand sea lion |
Physical Description
Adult males reach an average length of 2.0 - 3.25 meters and mass of 300 - 450kg. Their fur is dark brown to black.
Adult females average about 1.6 - 2.0 meters in length and a mass of up to 160kg. Their fur is buff to creamy-grey.
Newborn pups are 0.7 - 1.0 meters in length and have a thick coat of light or chocolate brown fur. Male pups are only modestly heavier than female pups, with an average mass of 7.9kg for the males pups compared to 7.2kg for the female pups.
Reproduction
New Zealand sea lion breed in colonies between November and January.
In November, the males ("bulls") arrive at the rookeries and engage in largely ritualistic fights to establish dominance over territory on the beach.
Females come ashore a few weeks after the males and join harems of 8 to 25 females on the territories of the sucessful males (referred to as "beach masters").
The females give birth shortly after arrival at the breeding site and mate a week to ten days later.
About 10 to 14 days after a pup is born, its mother starts leaving to feed at sea and returning every 2 - 3 days to nurse the pup, these feeding trips lengthening as the pup gets older.
The pup starts swimming by about 2-3 weeks of age and the mother continues to nurse her pup for at least 8 months, sometimes for a year or more.
Adult males typically stay on the beach and fast during the breeding season.
Female New Zealand sea lions become sexually mature at 3-4 years of age, males at 5 years. Males do not reach social maturity however until they are at least 8 years of age.
Lifespan/Longevity
Male New Zealand sea lions may live as long as 23 years, females as long as 18 years.
Behavior
Adult New Zealand sea lions dive regularly to a depth of 300m and have been reported to reach depths of over 600m.
Moulting occurs in late February through to early May.
While New Zealand sea lions may swim considerable distance on feeding trips there does not appear to be any partern of regular migration.
Distribution
The New Zealand sea lion is found only in New Zealand and breeds almost exclusively on New Zealand's subantarctic islands, in particular Dundas Island in the Auckland Islands where over 95% of all New Zealand sea lion are born in three close colonies. New Zealand sea lions have been observed ashore on islands ranging from the Macquarie Island to the southeast coast of South Island, New Zealand. rare sightings have been made on North Island of New Zealand .
In January 1998, a mysterious illness killed over half of the new born pups and perhaps one-fifth of all adults. Before this event, there was believed to befrom 12,000 - 14,000 New Zealand sea lions.
 New Zealand sea lions on Enderby Island in the Auckland Islands. Source: Mila Zinkova/Wikipedia |
 New Zealand sea lions on Enderby Island in the Auckland Islands. Source: Mila Zinkova/Wikipedia |
Habitat
New Zealand sea lions prefer sandy beaches. They will often move inland for up to 2km.
Food Habits
New Zealand sea lions are opportunistic feeders and the majority of their diet consists of cephalopods (such as squid and octopus), crabs, crayfish and many species of fish. The occasional penguin and fur seal are also eaten. Evidence has shown that although they start feeding close inshore, New Zealand sea lions travel up to 130km offshore during feeding trips. White pointer sharks and killer whales prey on adults and pups. Adult male New Zealand sea lions have also been observed killing and eating sea lion pups.
Conservation Status
The New Zealand sea lion, like other eared seals, was hunted for its skin and oil until the early part of the 20th century.
The New Zealand sea lion is designated as "Threatened" under New Zealand's Marine Mammals Protection Act and as "Vulnerable" on the IUCN Red List.
It is believed that hunting by Moari may have resulting in the species disappearing from the Chatham Islands.
Threats
New Zealand sea lions are vulnerable to entanglement and drowning in the nets of the squid fishing boats. The government of New Zealand has stepped in to restrict fishing when sea lion mortalities have risen above a declared limit (the precise number has been the subject of legal proceeding in New Zealand and wasset at 113 in December 2008). Devises and methods to limit sea lion deaths are being developed and tested.
The species is particularly vulnerable because of its restricted number and close proximity of breeding sites.
In January 1998, a mysterious illness killed over half of the new born pups and perhaps one-fifth of all adults.
Further Reading
- Phocarctos hookeri (Gray, 1844) Encyclopedia of Life (accessed April 8, 2009)
- Phocarctos hookeri, Rouse, I., 2001, Animal Diversity Web (accessed April 8, 2009)
- New Zealand sea lion, Seal Conservation Society (accessed April 8, 2009)
- The Pinnipeds: Seals, Sea Lions, and Walruses, Marianne Riedman, University of California Press, 1991 ISBN: 0520064984
- Encyclopedia of Marine Mammals, Bernd Wursig, Academic Press, 2002 ISBN: 0125513402
- Marine Mammal Research: Conservation beyond Crisis, edited by John E. Reynolds III, William F. Perrin, Randall R. Reeves, Suzanne Montgomery and Timothy J. Ragen, Johns Hopkins University Press, 2005 ISBN: 0801882559
- Walker's Mammals of the World, Ronald M. Nowak, Johns Hopkins University Press, 1999 ISBN: 0801857899
- Hooker's sea lion, MarineBio.org (accessed April 8, 2009)
- Archaeology and holocene sand dune stratigraphy on Chatham Island, B. G. McFadgen, Journal of the Royal Society of New Zealand,1994.
