Hooker’s sea lion (Phocarctos hookeri)

Description

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Hooker’s sea lion fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Hooker’s sea lion description

Hooker’s sea lion, also known as the New Zealand sea lion, is one of the rarest and most threatened sea lions in the world ⁽²⁾. Adult males are dark blackish-brown in colour and have a distinct light mane that reaches down to their shoulders. Females are grey or buff-coloured, and have a paler belly. Males are much larger than females. Pups are born with a thick covering of dark hair, which is lost at some point after birth ⁽³⁾.

Also known as

hooker's sealion, New Zealand sea lion, New Zealand Sealion.

Size

Male length: 2.0 - 3.25 m ⁽²⁾

Male weight: 300 - 450 kg ⁽²⁾

Female length: 1.6 - 2.0 m ⁽²⁾

Female weight: up to 160 kg ⁽²⁾

Hooker’s sea lion biology

Breeding takes place in colonies between November and January ^{(4) (2)}. Bulls (males) arrive at the breeding beaches in November each year, and start to fight amongst themselves to establish territories. Those that successfully secure and hold a territory are known as ‘beach masters’ ⁽²⁾ and will have privileged access to a harem of females ⁽⁵⁾. Throughout the entire breeding season, the beach masters are unable to return to the sea to feed, as this would force them to relinquish their hard-won territory. Instead they rely on their reserves of blubber during this period ⁽⁵⁾.

Pregnant females arrive at the beaches around a month later than males ⁽³⁾. They give birth, usually to a single pup after arriving at the breeding beach, and mate after around a week to ten days ^{(3) (5)}. Two weeks after giving birth, the mother starts to leave the pup in order to feed at sea, returning to the beach so that the pup can suckle ^{(2) (3)}. She identifies her own pup by its distinctive calls ⁽⁵⁾. The pup begins to swim after two or three weeks, but it will suckle for a further eight months or more, and even up to a year ^{(2) (3)}. Sexual maturity is reached at three to four years in females and five years in males ⁽⁵⁾.

Hooker’s sea lion feeds on small fish, squid, octopuses, crabs, mussels and other invertebrates. The occasional penguin may also be taken ^{(3) (4)}. Whilst feeding, this species makes the deepest and longest dives of any sea lion in the world ⁽⁶⁾.

Hooker’s sea lion range

This species has a very restricted range ⁽⁴⁾ and breeds only on the sub-Antarctic islands of New Zealand ⁽³⁾. Over 95 percent of breeding takes place in just three colonies in the Auckland Islands ⁽²⁾. Outside of the breeding season, these sea lions haul out from the Australian sub-Antarctic Macquarie Island to the south-eastern coast of New Zealand’s South Island, with a few sightings of individuals on the North Island ⁽²⁾.

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Hooker’s sea lion habitat

Breeding and hauling out occurs on sandy beaches ⁽⁴⁾. For the fist six months of life, the pups explore the freshwater creeks and pools around the beach ⁽³⁾. The adults often wander as far as two kilometres inland ⁽²⁾ and can be found resting in forests or on grassy cliffs ⁽³⁾.

Hooker’s sea lion status

Classified as Vulnerable (VU) by the IUCN Red List 2007 ⁽¹⁾. Listed as a threatened species under New Zealand’s Marine Mammals Protection Act ⁽²⁾.

Hooker’s sea lion threats

During the nineteenth century, Hooker’s sea lion was killed for its hide and oil. Since 1893, however, killing this species has been illegal ⁽²⁾. Rabbits, which were introduced into the breeding islands of Hooker’s sea lion, caused a problem as pups were falling into the rabbit burrows, resulting in high pup mortality ^{(4) (2)}. Rabbits have since been eradicated and their burrows have been filled in ⁽²⁾. Currently, the most serious current threat is accidental by-catch in the nets of the squid fishing industry ⁽²⁾. This fishery has operated in the range of this sea lion since the 1970s, and has been a serious problem since then ⁽²⁾.

In January 1998 the Hooker’s sea lion population suffered a catastrophic mass mortality event, which is thought to have killed 53 percent of pups and a high percentage of adults that year ^{(7) (2)}. The cause of this mass mortality is unknown ⁽²⁾. Before this event there were an estimated 12,000 to 14,000 individuals ⁽⁷⁾. This species is exceptionally vulnerable because its breeding range is so restricted ⁽²⁾.

Hooker’s sea lion conservation

At present, a 20 kilometre Marine Mammal Sanctuary exists around the Auckland Islands, and the sub-Antarctic islands of New Zealand were granted UNESCO World Heritage status in 1998 ⁽²⁾. At present, steps are being taken to reduce the threat posed to the species from the squid fishing industry, including closure of the fishery by the Government when the estimated number of sea lions caught in the nets exceeds a set limit each year ⁽²⁾. Marine mammal escape devices are being tested, and there is increasing pressure on the industry to use net-free methods of fishing ⁽²⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

For more information on this species see:

• Seal Conservation Society:
  http://www.pinnipeds.org/species/nzslion.htm

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Glossary

By-catch

In the fishing industry, the part of the catch made up of non-target species.

Invertebrates

Animals with no backbone.

Territory

Areas occupied and defended by an animal, a pair of animals or a colony.

References

1. IUCN Red List 2007 (March, 2008)
   http://www.iucnredlist.org
2. Seal Conservation Society (March, 2004)
   http://www.pinnipeds.org/species/nzslion.htm
3. Animal Diversity Web (March, 2008)
   http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocarctos_hookeri.html
4. UNEP WCMC Species Database (March, 2004)
   http://www.unep-wcmc.org/index.html?http://www.unep-wcmc.org/species/data/species_sheets/nzsealio.htm~main
5. Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
6. Costa, D.P. and Gales, N.J. (2000) Foraging energetics and diving behaviour of lactating New Zealand sea lions, Phocarctos hookeri. Experimental Biology, 23: 3655 - 3665.
7. Seal Conservation Society- New Zealand Sea Lion Mass Mortality (March, 2008)
   http://www.pinnipeds.org/hookeri.htm