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New Zealand Fur Seal (arctocephalus
forsteri)
Description
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A pointy nosed seal with long
whiskers, visible external ears and body covered with two layers of fur. Fur
seals look almost black when wet, but may look lighter when dry.
Adult females: average length
1.2m, weight 40 kg.
Adult males: average length 1.6m,
weight 160 kg. |
Range
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The New Zealand fur seal is found
throughout New Zealand, western and southern Australia. |
Population
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In New Zealand, minimum estimates
of the population are 50 - 60,000, but this is almost certainly an
underestimate. Recent work in Otago has shown there was a population
increase of 25% per year between 1982 and 1994 and surveys in 1995 indicated
this was continuing.
A similar rate of increase has
been noted in the Nelson/Marlborough region and also in the Subantarctic
Bounty Islands. Since 1991, fur seals have recommenced breeding on the North
Island. In Australia latest estimates are 30 - 35,000 with an annual
increase of 16 to 19%.
Although there are no estimates
of population growth available for Southland, a nationwide survey in the
1970's showed fur seals in Southland accounted for over 40 % of the total
New Zealand population or 70% if the sub-antarctic islands are included. |
Predators
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Large sharks and killer whales
are the main predators of seals. Hooker's sea lions may occasionally take
juvenile fur seals in the sub-antarctic islands but this has not been
reported on the mainland. |
Diet
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A survey is currently under way
into the diet of south coast fur seals. Early results show that south coast
seals mainly eat arrow squid, octopus, barracuda, jade mackerel and hoki
mostly off the continental shelf in depths greater than 22 metres. |
Foraging Patterns
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The New Zealand fur seal dives
deeper and longer than any other fur seal. Female fur seals on the West
Coast are known to (occasionally) dive deeper than 238 m, and for as long as
I I minutes. Off the Otago Peninsula in summer, they feed almost exclusively
at night (88 - 97% of dives), as deep as 163m with a maximum recorded dive
time of 6.2 minutes.
Most dives are however of 1-2
minutes. Most of their prey are species which follow a vertical migration,
i.e. they come nearer the surface in the middle of the night, and sink back
to deeper depths during the day. The seals appear to follow these migrations
when they forage. Their summer foraging is concentrated over the continental
shelf, or near the slope. They will dive continuously from sundown to
sunrise. In autumn and winter, they dive much deeper with many dives deeper
than 100m. At least some females dive deeper than 240m, and from satellite
tracking they may forage up to 200km beyond the continental slope in water
deeper than 1000m. |
Human Impact
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New Zealand fur seals ranged
around New Zealand before the arrival of humans. They were taken as food by
Maori. The onset of European sealing saw heavy exploitation to the point
where they were almost wiped out.
In 1894 they were given full
protection. |
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