New Zealand fur seals are sexually dimorphic, with adult males reaching 1.3 times the length and 3 times the weight of adult females. The muzzle is moderately long, flat, and tapers in width and depth to a bluntly-pointed nose. The rhinarium is fleshy, wide, and especially in males, droops down slightly at the end. In adults, the vibrissae are cream to white and medium to long. The ear pinnae are long and prominent.
Adult males have a mane of elongated, coarse guard hairs covering the greatly enlarged neck, chest, and shoulders, which extends to the nape and the top of the head. The crown is somewhat rounded, due to the modest sagittal crest, and there is a slight forehead. The canine teeth of adult males are larger and thicker than those of females. Adult females, subadults and juveniles have a flatter head with a minimal forehead.
The fore flippers have a dark, sparse, short fur that extends beyond the wrist onto the middle of the dorsal surface of the flipper in a ‘V’ pattern that does not reach the rounded tip. The rest of the dorsal surface, and the palms of both fore flippers are covered with a hairless black leathery skin. The first digit is the longest, widest and thickest, and unlike most otariids has a relatively straight, rather than posteriorly curving, leading edge, giving the flipper a triangular look. Digits 2-5 are successively shorter. There is a small opening in the skin at the end of each digit for a claw that is usually reduced to a vestigial nodule, and rarely emerges above the skin. The claw openings are set back from the free edge of the flippers by cartilaginous rods that extend the length of each digit, and expand the size of the flippers.
The hind flippers have dark, short, sparse hair covering part of the proximal end of the flipper, and the rest of the dorsal surface, and the entire sole is covered in black leathery hairless skin. The hind flippers are long and each digit has a cartilaginous rod that adds a flap-like extension to each toe. The bones of the three central toes terminate at the position of the small nails that emerge through the skin on the dorsal surface, set back from the end of the flipper. The claws of digits 1 and 5 are vestigial like the claws on the fore flippers, and may or may not emerge from small openings set back from the end of the flaps. All of the flaps at the end of the flipper are of relatively equal length. The first toe or hallux and the fifth toe are somewhat wider than toes 2–4.
Adults are dark olive brown or gray brown above and paler below. The muzzle is variably paler, gray to rusty tan on the end, in the mystacial area, and around the line of the mouth. The ear pinnae and the area around their insertions are also paler. Adult females are paler on the undersides than males, and are also pale from the lower sides of the abdomen to the chest and neck. Pups are blackish, except for a pale muzzle and undersides. They molt to adult pelage at 2-3 months.
There is some variation in weights of adult males in the literature. Some ranges are up to a maximum of 250 kg, others to 200 kg. The largest male weighed at the Open Bay Islands of New Zealand was 154 kg. Adult males 8-12 years old had a maximum weight of 124 kg. Adult males are up to 2 m long. Adult females are 1.5 m and 30-50 kg. Pups average 3.3-3.9 kg and 40-55 cm at birth and males average 14.1 kg and females 12.6 kg around weaning at 290 days old.
The dental formula is I 3/2, C 1/1, PC 6/5.
Can be Confused With
New Zealand fur seals share their range with five other otariids: Antarctic, Subantarctic, and Australian fur seals, and New Zealand and Australian sea lions. Shape of the head and muzzle, presence of a dense underfur, coloration, size and prominence of ear pinnae, and length of the toes on the hind flipper readily distinguish New Zealand fur seals from both sea lions.
Australian fur seal bulls are larger and heavier but less stocky with a long head and wider, tapering, but blunter muzzle with a large rhinarium that extends well beyond the mouth. The leading edge of the fore flipper curves posteriorly, as opposed to the straighter edge of the fore flipper of the New Zealand fur seal. The guard hairs of the mane are longer, and the neck and shoulders much more massive and muscular than on New Zealand fur seal males. Males are pale gray brown to dark gray brown, but paler than New Zealand fur seal bulls. Females are fawn to medium gray brown, paler below and on the neck, and paler above than female and subadult New Zealand fur seals.
Distinguishing New Zealand fur seals from Antarctic fur seals is more difficult due to similar size, shape and coloration. Note the straighter leading edge of the fore flipper in New Zealand fur seals than in Antarctic and Subantarctic fur seals. Adult male Antarctic fur seals have extensive light grizzling on the mane, are darker than adult male New Zealand fur seals being dark brown to very dark gray, have a wider and shorter muzzle, smaller rhinarium, and steeper forehead. Separating females, subadults and juveniles out of range or isolated is problematic.
Subantarctic fur seals are uniquely colored. The back and rump of adult males is dark gray to brownish black, and the chest and neck through the muzzle, face and area around the eyes are cream with yellow to orange shading. The ear pinnae are short, mostly bare skin and dark, and attach in the dark pelage of the upperparts. There is also a tuft of longer pale fur in the dark crown above the eyes and behind the dark forehead.
Although the adult male is enlarged and thick in the shoulders and neck, he does not have a mane. Adult females have similar coloration to the males, but have less well-defined pale facial markings that can be shaded with dull yellow orange to light brown. In both sexes the top of the fore flippers is darker as is the area where the flippers attach to the sides. The underside of the abdomen is dark ginger to reddish brown. The fore flippers and hind flippers are proportionately short and wide.
New Zealand fur seals are distributed in two geographically-isolated and genetically-distinct populations. In New Zealand, they occur around both the North and South Islands, with small breeding colonies on the north, and larger colonies on the west and southern coast and islands of the South Island, and on all of New Zealand's sub-Antarctic islands. They are less common off the North Island, with no colonies, but occur as far north as the Three Kings Islands. They are present, but do not breed, on Macquarie Island in April and May.
A separate population occurs in the coastal waters and on the offshore islands of southern and western Australia, from just east of Kangaroo Island west to the southwest corner of the continent in Western Australia. Vagrants have been recorded in New Caledonia, and from a bone in a 14th century archaeological site in the Cook Islands.
New Zealand fur seals prefer rocky habitat with shelter, and locations more exposed to wind and weather. They will also readily enter vegetation. Little is known of distribution at sea, although they seem to prefer waters of the continental shelf and slope, and are found widely in waters over the Campbell Plateau, south of New Zealand.
Ecology and Behavior
New Zealand fur seals are polygynous. Males arrive at colonies in late October before females and acquire and defend territories with vocalizations, ritualized displays, and fighting. Male territories include an average of 5-8 females with averages varying between different colonies. Pupping and breeding occurs from mid-November to January. The number of animals ashore at rookeries declines rapidly in January. Male vocalizations include a bark or whimper, a guttural threat, a low-intensity threat, a full threat, and a submissive call. Females growl and have a pup-attraction call that is a high-pitched wail.
Most pups are born from late November to mid-December. Estrous occurs 7-8 days after a female gives birth, and they usually spend another 1-2 days ashore with their pup before departing and beginning a cycle of foraging trips and periods of pup attendance ashore. Pups are weaned when they are about 10 months old. Foraging trips are shorter when the pup is young and become longer as the pup gets older. In general the overall mean time ashore attending the pup is a little over 3 days, and is roughly equal to the mean time of all foraging trips combined of approximately 3.3 days.
Foraging dives by lactating females are almost entirely at night to a depth of 15 m with a maximum depth of 163 m. Mean dive duration is 50 seconds with a maximum of 6.2 minutes. Maximum depth of dive for the species is 275 m and length of dive is approximately 11 minutes.
New Zealand fur seals are considered non-migratory. At sea they actively groom and raft in a variety of postures typical of southern fur seals including the “jug handle” position while sleeping at the surface. They will also porpoise when traveling rapidly. Predators include killer whales, sharks, male New Zealand sea lions, and possibly leopard seals at sub-Antarctic islands.
Feeding and Prey
The diet varies by location and time of year. Nearly all foraging by lactating females occurs at night. Important prey species include both vertically migrating species, and other species that occur throughout the water column and on the bottom. In New Zealand, Arrow and other squid species, barracouta, anchovy, various lanternfish species, jack mackerel, red cod, hoki, octopus, and penguins are important prey species. They also feed on shearwaters and possibly other flying marine birds.
Threats and Status
Humans have likely harvested New Zealand fur seals since first contacts occurred. There is evidence that Polynesian colonization of New Zealand and harvest of seals led to declines and loss of colonies on the coast of the North Island. European sealers nearly exterminated the species in the 19th century, but beginning with governmental protection starting in New Zealand and Australia in the late 19th century, the species has rebounded to occupy most of its former range.
Trawl and other fisheries are a source of entanglement and drowning. Tourism and disturbance at colonies can lead to disruption of breeding behavior and site abandonment, although most colonies are on offshore islands and are relatively inaccessible. The total population is estimated at approximately 55,000 to 85,000 with 35,000 of these in Australia. The last estimate for New Zealand of 30,000 to 50,000 is based on data compiled from the late 1960s to early 1980s. It is generally believed that the population has been growing since this period, and it has been suggested that the estimate may be low by half.
Arnould, J.P.Y. 2002. Southern fur seals Arctocephalus spp. pp. 1146-1151 in W.F. Perrin, B. Würsig and J.G.M. Thiewissen, eds. Encyclopedia of marine mammals. Academic Press.
Dickie, G. and S.M. Dawson. 2003. Age, growth, and reproduction in New Zealand fur seals. Marine Mammal Science 19(1):173-185.
Goldsworthy, S.D. and P.D. Shaughnessy. 1994. Breeding biology and haul-out pattern of the New Zealand fur seal, Arctocephalus forsteri, at Cape Gantheaume, South Australia. Wildlife Research 21:365-376.
Lento, G.M., R.H. Mattlin, G.K. Chambers and C.S. Baker. 1994. Geographic distribution of mitochondrial cytochrome b DNA haplotypes in New Zealand fur seals (Arctocephalus forsteri). Canadian Journal of Zoology 72:293-299.
Shaughnessy, P.D., N.J. Gales, T.E. Dennis and S.D. Goldsworthy. 1994. Distribution of New Zealand fur seals, Arctocephalus forsteri, in South Australia and Western Australia. Wildlife Research 21:667-695.