Fur seal pup, Wellington
Kekeno (Arctocephalus forsteri) are members of the Otariidae family of pinnipeds, fin-footed carnivorous marine mammals. They are distinguished by visible external ears and hind flippers which rotate forward.
This pointy-nosed seal has long pale whiskers and a body covered with two layers of fur. Their coat is dark grey-brown on the back, and lighter below; when wet kekeno look almost black. In some animals the longer upper hairs have white tips which give the animal a silvery appearance.
Adult females: maximum length 1.5 m, weight 30-50 kg.
Adult males: maximum length 2.5 m, weight 90-150 kg.
In New Zealand fur seals are found on rocky shores around the mainland, Chatham Islands and the sub-Antarctic islands (including Macquarie Island). Further they are found in South Australia, Western Australia and Tasmania. They are the most common seals.
Before the arrival of humans a population of about 2 million kekeno inhabited New Zealand. They were taken as food by Mäori. The onset of European sealing for meat and pelts in the 1700s and 1800s pushed them to the brink of extinction. Since their protection in 1978 numbers have increased gradually. Current minimum population estimates are 50,000-60,000 but this is almost certainly an underestimate.
Recent work in Otago has shown 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 sub-Antarctic Bounty Islands. Since 1991, fur seals have recommenced breeding on the North Island. In Australia latest estimates are 30,000 - 35,000 with an annual increase of 16 to 19%.
Overall the population seems to be recovering except for some colonies on the west coast of the South Island where a decline has been recorded. One of the possible reasons for this is the ongoing bycatch of mature females in the winter fishery for spawning hoki.
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.
Diet and foraging
Kekeno feed mainly on squid and small mid-water fish but also take larger species such as conger eels, barracuda, jack mackerel and hoki, mostly off the continental shelf.
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 11 minutes. Off Otago, fur seals feed almost exclusively at night and as deep as 163 m during summer. This is due to their prey species following 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. 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 100 m. At least some females dive deeper than 240 m, and from satellite tracking they may forage up to 200 km beyond the continental slope in water deeper than 1000 m.
Kekeno spend a lot of their time on rocky shores, at sites called haul-outs. Every year, these sociable animals return to the same area for the breeding season.
Females reach sexual maturity between 4 and 6 years and will give birth to a single pup more or less every year until their death at on average 14 to 17 years. Females mate 6 to 8 days after the birth of their pup, even before their first foraging trip. Delayed implantation means the egg is fertilised, but does not implant in the uterine wall for another 3 months. Gestation is therefore about 9 months, even though the female is mated 12 months before she gives birth.
The breeding season is from mid-November to mid-January. Pups are suckled for about 300 days, though some will continue to suckle into their second year. Females alternate foraging trips (periods of 1 - 20 days at sea) to feed, with attendance periods (1 - 2 days), where they are at the rookery to suckle the pup.
Pups start to feed on solid food before weaning, and spend a large proportion of time playing with other pups and objects such as seaweed and reef fish. It is possible that they attain skills for later life (such as foraging, anti-predator behaviour and also social behaviour) during this period. After weaning pups disperse.
Juvenile fur seals have been found over a 1000 km away from their place of birth. Males are sexually mature at 5 to 6 years, but are unlikely to be socially mature (able to hold a territory) for at least another 3 years. Dominant bulls put on displays of glaring and posturing and fighting with other males just prior to the breeding season to gain territories. Fur seals are polygamous breeders; this means that a male may mate with many females in a single breeding season.
Great white and sevengill sharks are the main predators of seals. New Zealand sea lions may occasionally take juvenile fur seals in the sub-Antarctic islands but this has not been reported mainland New Zealand.
Diet of fur seals Arctocephalus forsteri at Tonga Island, Abel Tasman National Park (PDF, 155K)