New Zealand fur seal (Arctocephalus forsteri)
Classified as Least Concern (LC) on the IUCN Red List (1) and listed on Appendix II of CITES (3).
The New Zealand fur seal has been recorded diving deeper and for longer than any other species of fur seal (2) (4). Fur seals, along with sea lions, are members of the Otariidae family, distinguished from true seals by external ears and forward rotating hind flippers, which assist with movement over land (2) (5). The New Zealand fur seal has a distinctly pointed muzzle with a somewhat bulbous nose, and long pale whiskers (2) (6). The adult males is up to three times the weight of the adult female, and has a massive neck with a coarse mane that extends from the top of the head down to the chest and shoulders (7) (8). The adult coat is generally dark grey-brown above (appearing almost black when wet) and paler below, with the female being notably paler on the underside of the neck and chest (6) (8). New Zealand fur seal pups are initially blackish, except for a pale muzzle and undersides, but moult into the adult coat after two to three months (1) (6) (8).
The New Zealand fur seal occurs in two geographically isolated populations: one around New Zealand and the other along the south coast of Australia (1) (6) (9). The New Zealand population is concentrated around the South Island, with large breeding colonies on the western and southern coast, as well as on New Zealand’s sub-Antarctic islands. Although there are no fur seal breeding colonies on the North Island, it does occur as far north as the Three Kings Islands off the northern tip of New Zealand. The Australian population is found in the coastal waters and on the offshore islands of Western and South Australia (1).
The New Zealand fur seal generally tends to stay close to land and is typically found on rocky shores where it readily enters areas of coastal vegetation behind the shoreline (1) (6) (7). At sea, it is thought to prefer waters of the continental shelf and slope (6).
New Zealand fur seals return to the same breeding sites each year (2), with the males arriving in late October to establish territories prior to the arrival of the females (1). Territories are defended through vocalisations, threatening displays and in about one in three encounters, actual physical fighting, where the combatants wave their necks from side to side and attempt to inflict bite wounds on the face, neck and shoulders (1) (7). The adult females arrive at the breeding sites from late November to December, and shortly after (usually just two to three days) give birth to the young that were conceived a year before during the previous breeding season (7). Around six to eight days after giving birth, the females mate again, but continue to attend to the pups onshore, while periodically undertaking foraging trips that become longer and longer as the pups get older. The pups are usually weaned at around ten months old, with females reaching 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 (1) (2) (7). As polygynous breeders, dominant males will mate with multiple females in a single breeding season, with each male territory comprising an average of five to eight females (1) (2). The gestation period is nine months, but an initial three month period of delayed implantation, where the fertilised egg does not implant in the uterine wall, results in the year long interval between mating and giving birth (2).
During the non-breeding season, from March to September, 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. Similarly, adult males spend substantial time ashore in non-breeding colonies, where a hierarchy is established based on size (7). The New Zealand fur seal has a varied diet comprising squid, octopus, and fish, and occasionally even birds, such as penguins and shearwaters (1) (2) (7). Although it normally dives in search of prey for no longer than one or two minutes (2), some individuals have been recorded at depths of almost 400 metres, staying underwater for over 14 minutes at a time (1). At sea, the New Zealand fur seal actively grooms, and will raft up to sleep in a variety of postures including the jug-handle position typical of many southern fur seal species (1) (6). Predators of the New Zealand fur seal include killer whales, sharks, sea lions and possibly leopard seals at the sub-Antarctic islands (1).
Although New Zealand fur seals were almost certainly harvested by indigenous people for food, it was European settlers, with a demand for seal skins, that decimated the population during the 19th century (1) (2) (7). Owing to increasing levels of protection, which began with regulations on sealing at the end of the 19th century, the population fortunately has rebounded. However, it still occurs as bycatch in commercial fisheries, through entanglement in nets and drowning, and is vulnerable to disturbance and pollution (1) (2).
The New Zealand fur seal is protected throughout its range by both Australian and New Zealand law. Despite incidences of bycatch in commercial fisheries, the population, which now numbers around 200,000, appears to be increasing, while the breeding range is still expanding (1). The focus of conservation work is to continue monitoring the population and to assess measures of reducing fishing related mortality (2).