New Zealand fur seal
New Zealand Fur Seal. Source: Peter Baum
The New Zealand fur seal (scientific name: Arctocephalus forsteri) 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.
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.
Like other Eared seals, the male New Zealand fur seal is considerably larger than the female.
Like other fur seals, the New Zealand fur seal was long hunted for its skin and oil and is now largely protected.
The New Zealand fur seal is considered by some not to be a disinct species but a subspecies of the South American fur seal (Arctocephalusaustralis) and thus should have a scientific name Arctocephalusaustralis forsteri.
 New Zealand Fur Seal. Source: Petr Baum/BioLib/Encyclopedia of Life |
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Conservation Status  |
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Scientific Classification Kingdom: Animalia (Animals) |
| Common Names Antipodean fur seal Australasian fur seal Black fur seal South Australian fur seal |
Contents
Physical Description
Extreme sexual dimorphism characterizes this species: while the average female weighs approximately 40kg and is 1.2m in length, the average male weighs close to 160kg. and is 1.6m in length.
New Zealand fur seals have sharp, elongate snouts and external, visible ears. They are covered by two layers of fur which is actually dark brown, but when wet Arctocephalus forsteri may appear black
Reproduction
Females New Zealand fur seals reach sexual maturity between 4 and 6 years of age, and males become sexually mature near 5-6 years old but do not begin to attain and defend territories once they reach approximately 8-10 years of age.
Breeding males come to shore in early November to compete for and establish territories. New Zealand fur seals are polygamous, with one male mating with up to 16 females.
Adult females begin arriving in mid-November to choose males. In Dec/Jan. females give birth to those pups conceived during the last breeding season.
Once the young reaches 6-12 days old, the mother begins going to sea to feed. Females alternate between offshore foraging and onshore nursing and caregiving. Foraging trips become longer as the pup gets older. Females and pups can be found at the rookery throughout the year. Adult males remain onshore for the entirety of the breeding season, often not feeding for up to 2 months. They return to the sea by mid-January.
Females give birth to 1 pup nearly every year until their death around 14-17 years. Females mate 6-8 days after the birth of a pup, but due to delayed implantation of the blastocyst (which does not implant for 3 months), gestation periods last 9 months. Young are suckled for approximately 300 days before they are weaned.
Lifespan
There is uncertainty about the lifespan of the species. Fifteen years is considered typical, though some sources suggest that some females individuals may live to 25 years.
Behavior
Much work has been conducted in studying diving behavior. It has been observed that lactating females are constrained to areas near the breeding site. Further, it has been shown that most dive depths ranged from 12-18m, and the maximum depth observed was nearly 163m. Durations of dives were from 3.2 to 6.2 min, but the average dive length was much shorter (0.7-1.2min). Dives tended to occur nocturnally, and dive depth varied with time of night, with deepest dives being near dusk and dawn (perhaps because prey was just starting to either rise from extremely deep depths, or was beginning to fall back to deep depths after feeding). Duration of the dive was found to be correlated with the depth (deeper dives required more time).
Distribution of the New Zealand fur seal. Source: Mirko Thiessen/Wikipedia. Distribution
The largest concentration of New Zealand fur seals is, as its names suggests, New Zealand - particularly the on the rocky coastline of the southern part of South Island and on many of the offshore islands - specific locations include Open Bay Islands, Cape Foulwind, Cascade Point, Wekakura Point, the Otago Peninsula, the Nelson-northern Marlborough region, Fjordland and the islands of the Foveaux Strait. New Zealand has in excess of 50,000 of these seals.
The Bounty Islands are also home to about 21,500 New Zealand fur seals (1994 estimate).
Arctocephalus forsteri is also found in western and southern Australia, in particular Kangaroo island in the Neptune Islands chain.
Habitat
New Zealand fur seals oscillate between aquatic and terrestrial habitats. When in the ocean, they are observed both far and near from shore. During the breeding season, however, fur seals spend most of their time along a rocky coastline, especially preferring those areas with an abundance of large boulders, crevices and caves so as to shelter and provide protection for pups. Further, New Zealand fur seals prefer areas which are near sheltered water or intertidal pools
Food Habits
New Zealand fur seals primarily feeds on aquatic species such as arrow squid, octopus, barracuda and jade mackerel. The seals are found to feed beyond the continental shelf in depths greater than 22m. Because its prey includes many vertical migrators (those organisms that rise to the surface during the night to feed and sink during the day), fur seals are found to feed almost exclusively during the night. These seals have been observed feeding continuously from sundown to dawn. Occassionally New Zealand fur seals will also eat penguins.
Conservation Status
They are now protected by New Zealand's Marine Mammals Protection Act and are beginning to recover and re-colonize areas in their pre-exploitation range. Although presently it is not legal to hunt New Zealand fur seals for fur or meat, they are still extremely threatened by human populations. They are subject to pollution, which affects their health in addition to actually physically trapping and drowning them. New Zealand fur seals are also inadvertantly caught in hoki nets that are set for other aquatic species. There have been observed increases in their population, however, in recently years at rates near 16-19%, and their numbers are quoted at being near 60,000. Fortunately, the future of Arctocephalus forsteri looks promising despite pollution and accidental catching.
Economic Importance for Humans
In the 18th and 19th centuries, New Zealand fur seals were widely hunted for food by the Maori people. With the onset of European sealing industry, fur seals were hunted for their fur in addition to their meat. Starting in 1894, however, both of these activities were deemed illegal and the New Zealand fur seal was granted full protection. Often fur seals interfere with commercial fishing equipment by becoming tangled in nets. In these instances they are usually killed. Further, many fishermen intentionally try to capture and kill them due to the belief that the seals deplete commercial fish stocks. It has been shown that fur seals eat minuscule amounts of commercially important fish and instead the bulk of their diet consists of organisms not used by humans. Unfortunately, however, the practice of killing them continues.
Further Reading
- Arctocephalus forsteri (Lesson, 1828) Encyclopedia of Life (accessed April3, 2009)
- Arctocephalus forsteri, Landes, D., 2000, Animal Diversity Web. (accessed April 3, 2009)
- New Zealand fur seal, Catalogue of Life (accessed November 24, 2009]
- New Zealand fur seal, Seal Conservation Society (accessed April 3, 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
- New Zealand fur seal, MarineBio.org (accessed April 4, 2009)
