New Zealand fur seal
New Zealand fur seal
IUCN status (2008): Least Concern
Distribution and population size
The New Zealand fur seal ('Kekeno' in New Zealand) occurs all around the coast of New Zealand, breeding mainly in the South Island (Taylor et al, 1995), and also on neighbouring offshore Islands extending towards the Antarctic fringe (Bonner, 1994). These islands include Chatham Island, Bounty Islands, with more than 4,000 pups born annually in 1994 (Taylor 1996), Antipodes Islands, where most seals are yearlings and older juveniles, with only occasional breeding activity (Taylor 1992), Macquarie Island, where again only non-breeding animals occur (Shaughnessy & Fletcher 1987) as well as Campball and Auckland Islands. The New Zealand fur seal also occurs along the southern and south-western coast of Australia, where it has been recently been distinguished from the closely related Australian fur seal (A. pusillus doriferus) (Ling, 1987, Shaughnessy et al 1994; 1996), which is found mainly in southeastern waters around Tasmania, Victoria and New South Wales (Bonner, 1994).
Total population size was estimated at about 50,000 in New Zealand with a further 5,000 in Australia (Bonner, 1994), but is now considered to be around 200,000 and gradually increasing (Goldsworthy & Gales, 2008), with about half the total population in Australia. On the Otago peninsula (Dunedin, SE South Island, New Zealand) the fur seals were considered to be a non-breeding assemblage of juveniles, but has since gradually become a significant breeding area, with more than 1,100 pups born by 1994 (Lalas & Harcourt, 1995). The highest rate of local population increase has been recorded at Kangaroo Island in Australia, with >12% per annum. This is considered to be a delayed population recovery about 70 years after harvesting ceased, the delay possibly due to fisheries-bycatch (Shaughnessy et al. 1995).
Fur seals at breeding colony on the Otago Peninsula, South Island, New Zealand. Photos: Sue Wilson
The New Zealand fur seal was historically hunted to local extinction, first by the Polynesian settlers to New Zealand and then even more thoroughly by European hunters in the 19th century. One report of 60,000 skins from Antipodes islands in 1804-05 was surpoassed by a report in 1814-15 of 400,000 skins being taken over the two-year period (Taylor, 1992). The species survived only in very low numbers to the turn of the 20th century, with breeding in new Zealand confined to the southern and western part of South Island and the sub-Antarctic islands (Taylor et al, 1995). It has been suggested that the original fur seals of Macquarie and the Antipodes islands may not have been A. forsteri, but may have been a species with more luxuriant fur, and therefore more vulnerable to hunting - which may have been the sub-Antarctic fur seal (A. tropicalis), or indeed another species which may have been completely extinct (discussed by Taylor, 1992). Small numbers of A. tropicalis and the Antarctic fur seal, A. gazella, now breed on Macquarie Island (Shaughnessy et al., 1988).
Growth and maturity
New Zealand Fur Seals are a medium sized fur seal and, as all fur seals, are sexually dimorphic, with the adult male-female ratio in body weight of about 3.5:1 (Bonner, 1981). The weight of adult males ranges from about 120-185kg, and females about 40-70kg. Body length in adult males is abput 145-250cm and in adult females about 125-150cm (reviewed by Bonner, 1994). There is no sexual dimorphism evident at birth, with newborn pups of both sexes weighing about 3-4kg and 40-55cm (reviewed by Bonner, 1994). Some sexual dimorphism at weaning is reported, with male pups weighing an average 14.1 kg to female pups at 12.6 kg around weaning when they are approximately 290 days old Goldsworthy & Gales, 2008), but growth rates are similar until about 5 years of age, when females become sexually mature, but males continue to grow until sexual maturity at about 8-10 years (Dickie and Dawson 2003, McKenzie et al. 2007).
Pup birth and development
Pups are born between the beginning of December and the 3rd week in January. Pregnant females come ashore about 0.5-3 days before giving birth. Most pups were born after 2-7 mins labour, depending on head or tail presentation (McNab & Crawley, 1975). Most mothers sniffed and nosed their pups immediately after birth for about 15 min. Most mothers kept their newborn pups close to them by by taking the skin of the head and neck in their mouths (McNab & Crawley, 1975). Most mothers were quiet for the first hour after birth, whereas most pups were very active, looking around, sniffing and nuzzling their mothers and sniffing the rocks. Pup calls were frequent during the first few hours and were termed 'mother attraction' calls by Stirling (1970). Mothers also gave the 'pup attraction' call (Stirling, 1970) during the first hour.
Mother with very young pup, Otago peninsula, December 2013. Photo: Sue Wilson
Pups are suckled and closely guarded by their mothers for up to the first month (Stirling, 1970). Mothers often went to the sea briefly to immerse themselves in water, and then returned to their pups according to a specific location in the colony. After the first few weeks, mothers return to to the sea to forage, returning to suckle it after intervals of about 2-8 days (average 5 days) (Page et al., 2005). While the mother is away, pups remained in pup pods within a limited area of their birth site. From about 3 weeks of age pups formed into larger pods, and often engaged in 'play fighting', gently biting each other's necks, shoulders and mouths and pushing against each other (McNab & Crawley, 1975). From about 3 months of age pups on the beach 'play fight' continuously, biting anywhere on the body. By 9 months of age some chest-to-chest posturing , similar to that of adult males, begins to occur.
Mothers locate their young by first scanning the colony area from the sea, and then come out of the water, emitting a 'high-pitched rising screech'. Several pups may initially respond, also by a high-pitched screech, and approach the female. Several calls between mother and her rightful pup may be exchanged before mother and pup nose each other - the pup usually with evident excitement. The mother then leads it to a point where she rests and nurses it (Stirling, 1970). After a nursing bout, pups often initiated play with their mothers, which consisted of pup and mother gently mouthing each others' face and neck.
Young pups avoided water for the first few days after birth; being swept into the water by wave surges was usually fatal at this age (McNab & Crawley, 1975). Most pups are about 2 months old before entering the water voluntarily, usually in sheltered tidal pools, and starting to swim (Baylis et al., 2005). To investigate the development of diving and foraging, 21 pups between 5-10 months of age were fitted with time-depth recorders, as well as analysing pup scats from the rocks during the same period. Average time spent in the water was 26% and average sea trip duration was 6 hours. Most dives were less than 10m and average dive duration was 23 sec. Dive depth increased between June and September. Scat analysis found that 43% of the prey was fish, 36% crustaceans and 20% cephalopods and there was an increase in the proportion of scats containing prey remains towards October, when pups start to be weaned. New Zealand fur seal pups therefore have 4-6 months longer than Antarctic and northern fur seal pups in which to develop diving and foragiing skills while still suckling. NZ pups also have greater body size than their sub-polar counterparts (Baylis et al., 2005).
Pups may also gather in pods inland while their mothers are feeding at sea. A well known pod occurs at the Oahu waterfall and stream near Kaikoura in the NE North Island. Pups go upstream from the beach, play in the pool at the base of the waterfall and also climb up the rocks into the forest to explore. See these video clips:
Juvenile fur seals assemble mainly in separate colonies from breeding animals, with very large colonies of juveniles, for example, on the Antipodes and Macquarie Islands (Taylor, 1992; Shaughnessy & Fletcher, 1987). Stirling (1970) describes a non-breeding colony at Kaikoura, where there were about 800 subadults at that time hauling out in winter (May-July), with fewer animals hauling out in the summer (November-January - the main breeding period). He described larger seals predominating in outer offshore rocks and also on the edge of the mainland, whereas younger juveniles mainly in groups, were found, mixed with some adults, in the middle offshore rocks - i.e. some stratification by age, with younger juveniles in locations potentially 'safer' from predators.
Yearling just emerging from water at Aramoana point, Dunedin - photo: Sue Wilson
Stirling (1970) describes interactions between juveniles onshore as 'aggressive posturing, challenges and extended fights lasting an hour or more, with no apparent victor at the end. The open mouth display may occur, sometimes by the submissive animal. Such a sequence between two juvenile males occurred when one male approached a sleeping, smaller male and challenged him with an neck display (see photos below). The smaller seal responded defensively with the open-mouth display, and after a little more posturning, both youngsters went back to sleep a short distance apart.
Altercation between two juvenile males, Aramoana Point (Dunedin), December 2013. Photos: Sue Wilson
It seems to be quite typical of NZ fur seals to rest ashore a short distance from one another - i.e. onshore they are gregarious, but maintain a small personal space of up to 1-2m (see photos below).
Non-breeding fur seals resting, December 2013 - Otago peninsula (left), Milford Sound (right) - Photos: Sue Wilson
Adult annual cycle
Adult males begin to come ashore at the breeding grounds in the spring (September) but do not start to compete for territories until the beginning of summer (November) (striling, 1970). Their agonistic behaviour towards one another is quite ritualised, starting with the 'full neck display': two males facing one another rear up so their necks are in a vertical position, thus displaying the thickness of their neck, and the male with the thickest neck usually 'wins' the encounter! if the smaller animal does not back off, the neck display escalates into 'neck waving'. Actual fighting only occurs if neck waving 'fails' to reach a resolution, and usually occurs between two males of the same size (Stirling, 1970). The breeding male's general 'alert' posture is non-aggressive (see top right photo above).
Breeding males each have up to about eight females with pups in their territory (Stirling, 1970). Females come into oestrus 1-2 weeks after giving birth, and are only receptive for ~24 hours and copulate usually only once with the resident male. During this breeding period, resident males try to prevent 'their' females from leaving their territory by intercepting them near the boundary, adopting a broadside upright posture beside them and the edging them away from the territory by shuffling sideways to push them gently away. Males herded females whether or not they had alreasdy mated (Miller, 1975). However, females intent on returning to the sea usually manage to escape when the male's attention is directed elsewhere! By the end of January many of the breeding males have left the colony to return to sea. The remaining males still defend their territories from other males, but pay little attention to females' movements in and out of their territory at this time.
Lactating females foraged relatively close inshore along the continental shelf, diving to an average of 40m for ~3 min, with a maximum of 312m for 9 min (Page et al., 2005). During December and January (i.e. when the pups were very young) the females came ashore for ~4.3 days at a time, but this reduced to ~1.8 days from February to November (i.e. when their pups were ~2-11 months old). Average time spent away from the rookery was 3-15 days (Mattlin et al., 1998). Adult males, by contrast, foraged in deeper waters beyond the continental shelf, typically diving tomore than 50m (up to 380m!) for ~4 min on average, with a maximum of 15 min (Page et al., 2005a). Females forage further offshore in Autumn, but inshore again in winter (Harcourt et al., 2002). The females ate mainly arrow squid in summer and autumn, but preferred an inshore benthic fish (the ahuru) in winter (Harcourt et al., 2002).
A study in southern Australia investigated possible competition for prey between adult males of the NZ and Australian species as well as among juveniles, females and males of the NZ fur seal (Page et al., 2005b, 2006). Adult females' diet tended to be generalist, dictated by prey abundance and the time constraints of being away from their dependent pups. Adult males of both species, however, ate larger, more energy-rich prey. Juveniles ate small pelagic fish from waters south of the continental shelf, suggesting that they avoided competition with adults of both sexes (Page 2005b). Juveniles travelled further from the colony than adult females, up to 1000km south of the habitats used by adults, but foraged closer to the colony during their summer moult. The authors suggest that juveniles do not have the capacity to spend enough time underwater to forage on benthic prey as adults are able to do (Page et al., 2006).
Fur seal rolling about at sea surface, Otago peninsula. Photo: Sue Wilson
Legal status, threats and conservation
Fortunately the commercial slaughter of New Zealand fur seals has receded into history. In New Zealand all marine mammals are protected by the Marine Mammals Protection Act of 1978. Management is driven by Conservation Plans developed by the Department of Conservation (DOC). The current plan, written in 2004, is an action plan for conservation of all marine mammals from 2005-2010 (Suisted and Neale 2004), and this plan seems to be still extant at the time of writing (January 2014). In Australia, State Governments have jurisdiction over marine mammals within three miles of the coast and each state has its own conservation legislation. The Australian Commonwealth Government has jurisdiction from three miles offshore throughout the rest of the countries’ 200 mile EEZ. An action plan for conservation of Australian seals was published in 1999 (Goldsworthy & Gales, 2008). The NZ fur seal is listed in CITES Appendix II i.e. international trade involving this species is subject to control).
It is known that there is significant mortality of NZ fur seals in commercial trawl fisheries, particularly in the hoki (inshore) fishery, with few seals being reported caught in deepwater or scampi fisheries. In 2007-08 an estimated 715 seals were caught in NZ trawl fisheries, with the capture rate estimated at 0.98-1.55 seals per 100 tows in 2006-08. The estimated capture rate was highest in the winter months of July-September, and capture rate was reduced in fisheries >90km from the shore (Thompson et al., 2010). In South Australia it is estimated that nearly 1,500 seals die from entanglement every year in debris such as loops or packing tape and trawl net fragments. Despite Australian Government and fishing industry initiatives to introduce guiding principles to reduce marine discarding of net and other debris, no significant reduction in entanglement was recorded (Page et al., 2004).The NZ DOC conservation plan aims to mitigate fur seal mortality in all NZ trawl fisheries.
New Zealand fur seals are the focus for much tourism in New Zealand's South island, with many colonies having a flourishing tourist industry. The DOC recommendation is for people to maintain a 10m distance from seals. The DOC aim with regard to tourism is to ensure 'appropriate behaviour of people around fur seals on beaches and in seal colonies'. However, a recent study (Boren et al, 2002) found that fur seal behaviour was disrupted by some tourist approaches, and recommended that the minimum approach distance on foot or in boat should be 30m and 20m by kayaks. They recommended that tourists should not enter a breeding colony on foot at all. However, it was not clear from the Boren et al. paper whether the disrupted behaviour was at breeding or non-breeding colonies.
This article was written following a visit to the Otago Peninsula area of New Zealand. My thanks to Elm tours for taking us to the breeding colony of fur seals - which we were able to view from a purpose-built viewing point on the cliff above the seals, so there was no disturbance at all to the colony. We also visited Aramoana Point and - with thanks to Maureen Howard and Mike Hazel - Allen's beach, where in both places we found small numbers of non-breeding fur seals resting onshore. Most seals we encountered were asleep and did not wake up when we approached. Exceptions were a yearling (who spotted me from the sea and hauled out, apparently to take a closer look at me (see photo above), and then returned to the sea) and two young males, whose altercation is described above, and who paid absolutely no attention to my presence. We took great care not to disturb them, staying more than 10m away. There were also other people at Aramoana Point and Allen's beach, and all people we saw behaved with great respect towards the seals. - Sue Wilson
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