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Arctocephalus forsteri

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Arctocephalus forsteri
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Otariidae
Genus: Arctocephalus
Species:
A. forsteri
Binomial name
Arctocephalus forsteri
Lesson, 1828
Distribution of the New Zealand fur seal

Arctocephalus forsteri, the Australasian fur seal, South Australian fur seal, New Zealand fur seal, Antipodean fur seal, or long-nosed fur seal, is a species of fur seal found mainly around the South and Western coasts and offshore islands of Australia, and the North Island and South Island of New Zealand.[1] The name New Zealand fur seal is used by English speakers in New Zealand; kekeno is used in the Māori language.[2][3] As of 2014, the common name long-nosed fur seal has been proposed for the population of seals inhabiting Australia.[4]

The seal is native to Macquarie Island, South Australia, and Western Australia, and the North Island and South Island of New Zealand.[1] Although the Australian and New Zealand populations show some genetic differences, their morphologies are very similar, and thus they remain classed as a single species.[1]

Description

Males have been reported as large as 160 kg; their average weight is about 126 kg.[1][5] Males can be 2 metres long. Females are between 30–50 kg on average, and can be as long as 1.5 metres. Pups are 3.3–3.9 kg on average, and between 40 and 55 cm long. At 290 days old males are about 14.1 kg, and females are about 12.6 kg.[1] They have external ears and hind flippers that rotate forward, which visibly distinguish them from other seals.[2] They have a pointy nose with long pale whiskers.[2] The fur seals are covered by two layers of fur. The coat is grey-brown on their back, and lighter on their belly.[2] Some have white tips on longer upper hairs, which can give them a silver-like appearance.[2]

So called "Upland Seals" once found on Antipodes Islands and Macquarie Island have been claimed as a distinct subspecies with thicker furs by scientists although it is unclear whether these seals were genetically distinct.[6]

Behaviour

Diving

The species can "porpoise" out of the water when travelling quickly at sea.[1] They can dive deeper and longer than any other fur seal.[2] Females can dive for about 9 minutes and to a depth of about 312 metres, and can dive deeper and longer in autumn and winter. Males can dive for about 15 minutes to a depth of about 380 metres.[1] On average, the species typically only dives for 1–2 minutes.[2] When they dive for food they dive deeper during the day but shallower at night, because during the day their prey typically migrates to deeper depths and migrates back up during the night.[2]

Lactating females alter their dive patterns in order to regularly care for their young. Dives are shorter, from around 9 minutes down to 5 minutes. Several longer trips may be taken at first to find patches of prey. The shorter dives then utilise these patches. Due to the differences in diving pattern between males and females, there is very little inter-sexual competition for food sources. Males typically forage over continental shelf breaks in deeper water, while females typically utilise the continental shelf as foraging grounds. It is believed that differences in diving abilities and depths could be the cause of some sexual dimorphism between males and females.[7]

Diving behaviour by the pups begins in the months leading up to weaning, when the pups are nursing less. The pups begin to dive from the age of 6–10 months, yet weaning is known to occur between the ages of 8 and 11 months, so the young pups do not have much time to learn to forage. The pups need to progressively develop nocturnal diving skills while they still have their mothers' milk to fall back on if dives are unsuccessful. Age, physiological development, and experience are important factors for success in hunting and contribute to the development of the pups' diving ability and behaviour. This transitional period when young pups are becoming nutritionally independent while their foraging efficiency is rather low, is a time of high risk, and mortality can be very high. Based on scat samples, it has been found that the pups start by eating cephalopods and eventually making their way to fish, but this may just be a result of prey availability during different times of the year.[8]

Communication

Males vocalise through a bark or whimper, either a gluttural threat, a low-intensity threat, a full threat, or a submissive call. Females growl and also have a high-pitched pup attraction wail call.[1] Pup-attraction calls allow communication from longer distances. Once together, females use olfactory recognition to confirm the pup as their own.[9] In males, the full neck display is a non-combative posture that functions as a threat to surrounding males by which they are able to assess each other's dominance status.[9]

Arctocephalus forsteri near Kaikoura, New Zealand

Reproduction

Females mature between 4 and 6 years old, and males mature between 8 and 10 years old.[1] These seals are polygynous.[1][2] Males obtain and guard territory in late October before females arrive.[1] Often females mate only once a year, and this usually occurs eight days postpartum for about 13 minutes on average. Females have a delayed implantation of the fertilised egg, so that implantation on the uterine wall does not occur for 3 months.[2] Gestation occurs for 9 months[2] Females are more aggressive near the time of birth, and do not like to be approached right after birth.[5] Females will continue to reproduce until their death which is on average between 14 and 17 years of age.[2]

Females first arrive on the shore between November and January,[1] just a few days before giving birth, and stay close to the birth site for up to ten days. When they are close to labour they become very restless and irritable. When beginning labour, which can last as much as five hours, they lie down and toss their head in the air, straining forward on their fore flippers, lifting their hind quarters, or moving laterally, before slowly lowering their head down, a process they repeat until they finally give birth. In one study, observations of the actual birth, starting from when the pup was first seen, found an average of 2 minutes for a head-first delivery, but an average of 6.5 minutes if the pup came out tail first. Immediately after birth the mother begins frequently sniffing the newborn pup to better identify when she has to find it after a trip out to sea. Pups are fairly mature at birth, and within 60 minutes they start suckling for about 7 minutes. Eventually the suckling can exceed 33 minutes.[5]

The mothers may take from 45 minutes to 3 days before leaving the pups to swim, and 6–12 days to go on longer feeding trips. Even then the mothers tend to not leave the pups for longer than 2 days. When the pups are about 21 days old they have been seen to congregate into little pods while their mothers are away. When the females return they only feed their own pups, and have been seen to be hostile toward pups that are not their own.[10]

Female seals have been documented to have a gradual increase in trips for feeding throughout lactation. It has been found that mothers who have sons made longer foraging trips then the mothers who had daughters during the lactation period. When observing growth patterns in the male and female pups within two cohorts, it is recognised that the growth patterns are similar, however the males grow faster and are weaned off nursing heavier in some years.[11] Suckling can occur for about 300 days. Pups start to eat solid food just before weaning,[2] and are eventually weaned around September, when they disperse.[5][2]

Pup mortality has been attributed to both natural factors and human interaction. The biggest natural cause of death for pups is starvation, followed by suffocation in the amnion, stillbirth, trampling, drowning, and predation.[12] Human factors include the handling of pups, tagging, and human presence in general.[12]

Diet

Their diet includes cephalopods, fish, and birds.[1] Octopus and arrow squid make up most of their cephalopod diet.[13] Individuals located near their southern range limit have been known to eat penguins as part of their diet.[13] Stomach contents have been analysed and shown to include anchovy, barracuda, flounder, hagfish, lamprey, red cod, school shark, and many other species.[14] Further analysis of otoliths from their scat show that for fish prey species, lantern fish composed the majority of their fish diet, followed by anchovies, pink cod, and hoki.[13] There are different factors that affect their diet, such as season, sex, breeding, surrounding colony, oceanography, and climatic patterns.[14]

Predators

Known predators are killer whales, sharks, male New Zealand sea lions, and possibly leopard seals.[1] New Zealand sea lions are also known to target pups as their prey.[15] Several regurgitations by sea lions have been found to contain remains of fur seal pups, some with plastic tags previously attached to female fur seal pups.[15]

Human impact

Notice informing the public, Napier, New Zealand

Seals were widely hunted from shortly after the European discovery of New Zealand until the late 19th century. The population in New Zealand dropped to under 10% of the original population. Today commercial fisheries are one of the main sources of death of New Zealand fur seals usually by entanglement and drowning.[1] Monitoring of these pinnipeds in the Kaikoura region found that entanglements with green trawl nets and plastic strapping tape were the most common.[16] A little less than half of the individuals were successfully released with good chances of survival even after significant entanglement wounds.[16] It has been estimated by the Royal Forest and Bird Protection Society that over 10,000 seals could have drowned in nets between 1989 and 1998.[5] They are also known to have been shot by commercial and recreational fishermen, because they are assumed to interfere with fishing gear. How often these shootings occur is unknown, but pressure groups have stated that the conflict between the seals and commercial fisheries is expected to increase.[17] On 21 August 2014, two decomposing animals were found beheaded near Louth Bay in South Australia. The circumstances of their deaths were considered suspicious and an investigation followed their discovery.[18] In 2015, several conservative members of Parliament encouraged public debate around the potential implementation of seal culling in South Australia in response to increasing interactions with South Australian commercial fisheries. As of July 2015, the killing of long-nosed fur seals remains an illegal act.

Human activity near seal rookeries have been correlated to distress and panic, resulting in indirect deaths of pups.[12] The use of metal cattle ear tags on pups has also been associated with a decrease in pup fitness due to incomplete healing of the tag site.[12]

Legislative protection

Australia

In Australian Commonwealth waters, Arctocephalus forsteri is protected under the Environment Protection Biodiversity Conservation (EPBC) Act 1999 under which it is listed as a protected marine species.[19] The species is also protected within the jurisdictions of the following Australian states:

State Listed as Legislation
New South Wales Vulnerable Threatened Species Conservation Act 1995 (NSW)[19]
South Australia Marine mammal National Parks and Wildlife Act 1972 (SA)[20]
Tasmania Rare Threatened Species Protection Act 1995 (TAS)[19]
Victoria Protected Wildlife Act 1975 (Vic)[21]
Western Australia Other protected fauna Wildlife Conservation Act 1950 (WA)[19]

The species received protection by the creation of a 16 million hectare Marine Park located on the eastern side of Macquarie island in 2000. The Tasmanian government has also extended to Macquarie Island Nature Reserve by 3 nautical miles surrounding the island.[17]

New Zealand

In New Zealand, the species is protected by the Marine Mammals Protection Act 1978, which works to conserve marine animal species; it specifies that all wild Pinnipeds cannot be touched or fed.[1]

See also

References

  1. ^ a b c d e f g h i j k l m n o p q Template:IUCN2008
  2. ^ a b c d e f g h i j k l m n Department of Conservation. "New Zealand fur seal/kekeno" Retrieved 6 October 2011.
  3. ^ "New Zealand fur seal video - Arctocephalus forsteri - 01". Arkive.
  4. ^ Chilvers, B.L.; Goldsworthy, S.D. (2015). "Arctocephalus forsteri. The IUCN Red List of Threatened Species". International Union for Conservation of Nature and Natural Resources. Retrieved 27 July 2015.
  5. ^ a b c d e Harcourt, R.G., (2001). "Advances in New Zealand mammalogy 1990–2000: Pinnipeds". Journal of The Royal Society of New Zealand, Retrieved 6 October 2011
  6. ^ Richards, Rhys (1994). ""The upland seal" of the Antipodes and Macquarie Islands: A historian's perspective". Journal of the Royal Society of New Zealand. 24: 289–295. doi:10.1080/03014223.1994.9517473.
  7. ^ Page, B., McKenzie, J., & Goldsworthy, S. (2005). "Inter-sexual differences in New Zealand fur seal diving behavior". Marine Ecology Progress Series. 304: 249–264 – via JSTOR.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ Baylis, A M.M; Page, B; Peters, K; McIntosh, R; Mckenzie, J; Goldsworthy, S (1 September 2005). "The ontogeny of diving behaviour in New Zealand fur seal pups (Arctocephalus forsteri)". Canadian Journal of Zoology. 83 (9): 1149–1161. doi:10.1139/z05-097. ISSN 0008-4301.
  9. ^ a b Ian Stirling; Observations on the Behavior of the New Zealand Fur Seal (Arctocephalus Forsteri), Journal of Mammalogy, Volume 51, Issue 4, 30 November 1970, Pages 766–778, https://doi-org.oca.ucsc.edu/10.2307/1378300
  10. ^ McNAB, A.G (1975). "MOTHER AND PUP BEHAVIOUR OF THE NEW ZEALAND FÜR SEAL, ARCTOCEPHALUS FORSTER" (PDF). MÄURI OR: 13.
  11. ^ Goldsworthy, Simon D. (13 April 2006). "Maternal strategies of the New Zealand fur seal: evidence for interannual variability in provisioning and pup growth strategies". Australian Journal of Zoology. 54 (1): 31–44. doi:10.1071/ZO05041. ISSN 1446-5698.
  12. ^ a b c d MATTLIN, R. (1978). PUP MORTALITY OF THE NEW ZEALAND FUR SEAL (ARCTOCEPHALUS FORSTERI LESSON). New Zealand Journal of Ecology, 1, 138-144. Retrieved from http://www.jstor.org/stable/24052393
  13. ^ a b c Carey, P. (1992). "Fish prey species of the new zealand fur seal (Arctocephalus forsteri, lesson)". New Zealand Journal of Ecology. 16: 41–46 – via JSTOR.
  14. ^ a b Boren, L. (2010) "Diet of New Zealand fur seals (Arctocephalus forsteri): a summary", Retrieved 6 October 2011
  15. ^ a b Bradshaw, C.J.A., Lalas, C., & McConkey, S. (1998). "New Zealand sea lion predation on New Zealand fur seals". New Zealand Journal of Marine and Freshwater Research. Retrieved 6 October 2011
  16. ^ a b Boren, L. J., Morrissey, M., Muller, C. G., & Gemmell, N. J. (2006). Entanglement of New Zealand fur seals in man-made debris at Kaikoura, New Zealand. Marine Pollution Bulletin, 52(4), 442-446.
  17. ^ a b MarineBio.org (2011). "New Zealand Fur Seals, Arctocephalus forsteri at MarineBio.org" Retrieved 6 October 2011.
  18. ^ "Headless fur seals found on beach in SA treated as suspicious". ABC. 25 August 2014. Retrieved 26 August 2014.
  19. ^ a b c d "Arctocephalus forsteri". Species profile and threats database. Australian Government—Department of the Environment. 2014. Retrieved 26 August 2014.
  20. ^ National Parks & Wildlife Act 1972. Government of South Australia. 2014.
  21. ^ "Seals and People A reference guide for helping injured seals" (PDF). Department of Sustainability and Environment. p. 16. Retrieved 25 June 2015.

Sources

  • Randall R. Reeves; Brent S. Stewart; Phillip J. Clapham; James A. Powell (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf, Inc. ISBN 0-375-41141-0.
Wikimedia Commons has media related to Arctocephalus forsteri.
  • New Zealand fur seal discussed on RNZ Critter of the Week, 28 July 2017
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