New Zealand fur seals, Arctocephalus forsteri, were named by Lesson in 1828.
Order: Carnivora
Sub-order: Pinnipedia
Family: Otariidae
Genus: Arctophoca
Size, shape and distinctive characteristics
NZ fur seals are sexually dimorphic with adult males reaching up to 150kg in weight and 2m in length. Females only reach 30 to 50kg and 1.5m in length. Pups are born 3 to 4 kg in weight, reaching 12 to 14kg by weaning. NZ fur seals have long tapered muzzles with slightly upturned pointed noses and long whiskers. Their bodies are covered in dark olive brown to gray fur which when dry has paler guard hairs showing through.
NZ fur seals share their distribution with three other fur seals which they could be confused with including Australian, Antarctic and Sub-antarctic fur seals. Hybrid NZ x Antarctic fur seals are known which show characteristics of both species.
The New Zealand fur seal is found on rocky shores around New Zealand, Chatham Islands, New Zealand's sub-antarctic Islands (including Snares, Bounties, Antipodies, Auckland, Campbell and Macquarie Islands) and in South Australia, Western Australia and Tasmania. Their numbers are expanding throughout their range except for the west coast of the South Island of New Zealand.
Ecology and Behaviour
New Zealand sea lions are polygynous breeders, dominant males will mate with multiple females in a single breeding season - November to January, with each male territory comprising an average of five to eight females.
During the non-breeding season - February to October, the breeding sites are occupied by pups and young juveniles, whilst adult females alternate between periods at the breeding sites and periods foraging at sea. Adult males tend to disperse away from breeding sites and spend substantial time ashore in haul - out areas.
The New Zealand fur seal has a varied diet comprising squid, octopus, and fish. Female fur-seals dive usually 70-80 metres during early lactation. Later in their lactation they will dive to depths of 20-200 metres and further out to sea (80-100 km from shore). It is highly likely that the males can dive over 200 metres. Although it normally dives in search of prey for no longer than one or two minutes, some individuals have been recorded staying underwater for over 14 minutes at a time. At sea, the New Zealand fur seal actively grooms, and will raft up to sleep. Predators of the New Zealand fur seal include killer whales, sharks and possibly leopard seals at the sub-Antarctic islands.
Life History
New Zealand fur seals have a regular and annual breeding season from late November to mid January, with pup births peaking in mid to late December. Bulls arrive at the colony prior to the commencement of pupping and fight aggressively with each other to establish and defend territories. After an extended time feeding at sea, females arrive at the colony 2-3 days before giving birth to their single live pup on shore. Females remain with their pup for about ten days, then depart to feed at sea, returning regularly to suckle their pup with rich milk. Pups are weaned between 8 and 12 months of age.
During the breeding season, female fur-seals are gathered into "harems" (usually 6-8 cows) by the bulls within their territories. 7-8 days after the birth of her pup, the female comes into season and is mated by the resident bull. The development of the fertilised egg is delayed for approximately 3-4 months, followed by an active gestation of 8-9 months. Bulls may stay on shore and not feed for up to 8 weeks as they defend their harem and their territories. Females reach sexual maturity at around four to six years and males at around five to six years. However, it is unlikely that a male will command a breeding territory until at least eight to ten years of age.
Diet
New Zealand fur seals feed mainly on squid, octopus and schooling fish, with a small proportion of their diet also being made up of birds. The proportion of squid and octopus in a fur-seal's diet is higher during the summer months and more fish are consumed during the winter. NZ fur seals feed mainly at night when prey rises closer to the surface, and resting during the day.
Global Abundance
From the early 19th century, NZ fur seals were hunted to economic extinction throughout its range. Since the late 1800s, when fur seals in New Zealand and Australia were protected, numbers have increased gradually.
In New Zealand over the last three decades, fur seal numbers have risen appreciably on the Bounty Islands, northern South Island (Nelson-Marlborough), and eastern South Island; Kaikoura and Banks Peninsula, Otago. Numbers on the Snares Islands appear stable since the 1970's. Similar increases have also been reported in their Australian distribution.
However, on the West Coast of South Island NZ fur seal pup numbers have declined by between 29% and 39% on three rookeries studied from late January 1991 to late January 2007. The cause of these declines has not been established however is likely to be related to ongoing bycatch of mature females in the winter fishery for spawning hoki, on top of natural losses of pup production, pup survival and yearling survival during periodic warming events.
IUCN status
The New Zealand fur seal are listed as of Least Concern by the IUCN.
Prehistoric hunting was pursued by native peoples of Australia and New Zealand. Commercial sealing by Europeans was carried out in earnest in the early 19th Century and the population of these fur seals in New Zealand, Australia and the subantarctic was drastically reduced and whole colonies were wiped out. There have been sporadic culls as numbers rebounded in the 20th Century. At present, New Zealand fur seals are protected throughout their range by New Zealand and Australian laws. Threats today include entanglement in fishing gear and debris, drowning due to by-catch in trawl or set nets and the potential depletion of their food resource base due to intensive commercial harvesting of fish and squid.
B. Louise
Chilvers, Dept of Conservation
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Arctophoca australis forsteri
