Phocarctos hookeri

Status_ne_offStatus_dd_offStatus_lc_offStatus_nt_offStatus_vu_onStatus_en_offStatus_cr_offStatus_ew_offStatus_ex_off

Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CARNIVORA OTARIIDAE

Scientific Name: Phocarctos hookeri
Species Authority: (Peters, 1866)
Common Name(s):
English New Zealand Sea Lion, New Zealand Sealion, Hooker's Sea Lion, Hooker's Sealion
Taxonomic Notes: The taxonomy of Phocarctos of New Zealand and Neophoca of Australia was confused until 1960 (Rice 1998).

Assessment Information [top]

Red List Category & Criteria: Vulnerable A3b ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Gales, N. (IUCN SSC Pinniped Specialist Group)
Reviewer(s): Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Justification:
The New Zealand Sea Lion has a relatively small population (<10,000 mature individuals) and a limited distribution. Most reproduction is restricted to a very few sites. The best population trend data (for pup production) are from 1994. Estimates prior to this are less reliable, and include a smaller proportion of the whole population. There has been a marked (30%) decline in pup production in the last 10 years, at some of the major rookeries. The reason for the decline is not clear, but is likely to be a combination of on-going fisheries by-catch of adult females and a series of bacterial disease outbreaks. New Zealand Sea Lions qualify globally as Vulnerable (VU) under criterion A3b. But, given the seeming increase in incidence and severity of disease outbreaks, and the EN (Endangered) status of some local populations, this species should be reviewed again within a decade.

IUCN Evaluation of the New Zealand Sea Lion, Phocarctos hookeri
Prepared by the Pinniped Specialist Group

A. Population reduction
Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.

Pup production has declined at the Auckland Island (where 86% of the population breed) by 31% in the period 1997/98 to 2005/06. For the four years prior to this, pup production had increased by about 20% in the same region. Overall pup production has decreased by 17% between 1994/95 and 2005/06 at the Auckland Islands. Regular estimates of pup production prior to the mid 1990s are only available for one of the Auckland Islands (Enderby Island; where about 20% of the population breed) and production numbers at this site show no statistical trend since about 1980. Data from Campbell Island (where almost all of the remaining 14% of the population breed) is too intermittent and of insufficient precision to derive meaningful trends. The mean age of reproduction of female New Zealand Sea Lions is 10.75 yrs, with some females giving birth at 3 yrs and living as long as 27 yrs. Causes of the decrease in pup production since 1997 are not clear, but may be related to the scale of fishery by-catch or three unusual mortality events that resulted in very high pup mortality.

A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

Fishery by-catch of an estimated 1-2% of adult female New Zealand Sea Lions continues in association with the New Zealand squid trawl fishery. The recent, unusual mortality events have been diagnosed to have resulted from bacterial infections, but the underlying reason for their current frequency and scale of effect of not known, nor their potential for future epidemics.

A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1.

If pup production since 1997 is primarily driven by by-catch and disease events, and these continue at current rates (mean of 4.1% decline in pup production since 1997), and we assume a three generation period of 30 yrs, then a decline of >70% will have occurred by 2027. This would qualify the species for EN under A3.

A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

If the rates of population decline since 1997 are less dependent upon the by-catch and epidemics (or these decline), and future rates of change average those prior to 1997, then the current dramatic decrease may be arrested and longer term trends may be <30% over 3 generations.

B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1.
Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²

The EOO is > 20,000 km².

B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²

The AOO is > 2,000 km².

AND at least 2 of the following:
(a)
Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.

C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000

The number of mature individuals may be < 10,000, given that total population size (which included the juvenile cohorts) was estimated to be 11,700 and 12,500 respectively in 1994/95 and 1995/96, at a time when pup production was about 17% greater than the most recent 2005/06 estimate. When scaled down to current pup production sizes (9,700 and 10,400 respectively) and juvenile cohorts are removed, then the number of mature individuals is likely to be <10,000.

AND either C1 or C2:
C1.
An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)

Between 2000-2005 pup production at the Auckland Islands decreased by about 27%.

C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
or
(a ii) % individuals in one subpopulation: CR = 90-100%; EN = 95-100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.

D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5

Does not apply.

E. Quantitative analysis
Indicating the probability of extinction in the wild to be: Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years

There has been no quantitative analysis of the probability of extinction.

Listing recommendation : The New Zealand Sea Lion has a relatively small population (<10,000 mature individuals) and a limited distribution. Most reproduction is restricted to a very few sites. The best population trend data (for pup production) are from 1994. Estimates prior to this are less reliable, and include a smaller proportion of the whole population. There has been a marked (30%) decline in pup production in the last 10 years, at some of the major rookeries. The reason for the decline is not clear, but is likely to be a combination of on-going fisheries by-catch of adult females and a series of bacterial disease outbreaks. New Zealand Sea Lions qualify globally as Vulnerable (VU) under criterion A3(b). But, given the seeming increase in incidence and severity of disease outbreaks, and the EN (Endangered) status of some local populations, this species should be reviewed again within a decade.
History:
1996 Vulnerable (Baillie and Groombridge 1996)
1996 Vulnerable
1994 Vulnerable (Groombridge 1994)

Geographic Range [top]

Range Description:The primary habitat of New Zealand Sea Lions is several sub-Antarctic islands south of New Zealand and their surrounding waters. The principal breeding colony accounting for 86% of annual births is at the Auckland Islands, with a smaller number breeding at Campbell Island (Chilvers et al. 2007). New Zealand Sea Lions regularly occur in small numbers at Stewart Island and on the southeast coast of the South Island of New Zealand, where there are occasional births (Chilvers et al. 2007). However, most of the animals hauling out on the South Island are males ranging in age from 2-11 years old. Wandering New Zealand Sea Lions also reach Macquarie Island. Historically, New Zealand Sea Lions had a more extensive range that appears to have included most of New Zealand.
Countries:
Native:
New Zealand (Antipodean Is., South Is.)
Vagrant:
Australia (Macquarie Is.)
FAO Marine Fishing Areas:
Native:
Pacific – southwest
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: New Zealand Sea Lions have a highly restricted distribution and a small population that numbers approximately 11,855 animals (Campbell et al. 2006). This equates to an adult population size of <10,000. Pup production has shown a decline of 30% in the last 10 years, but this was preceded by a few years of growth. Data from one of the main colonies shows no overall trend in pup production over the past 25 years (Chilvers et al. 2007).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: New Zealand Sea Lions are large heavy-bodied sexually dimorphic animals. Adult males are 1.2-1.5 times longer and 3-4 times heavier than adult females. Adult males are 2.3-2.7 m long and may weigh from 320-450 kg, although these values might be high in the light of recent information that males are probably shorter than previously reported. Adult females are 1.8-2 m long and weigh 90-165 kg. Newborns are approximately 70-100 cm long and weigh 8-10 kg (Chilvers et al. 2006). Pups are born in a thick long dark brown lanugo with a lighter crown, nape, and mystacial area, and with a pale stripe on the top of the muzzle, originating on the crown. Female pups are lighter than male pups. Pups begin to molt their birth coat at 2 months and at the end of the molt look like adult females.

Males become sexually mature at the age of 5 years. The age of maturity for females is 3-4 years. Gestation lasts 12 months. Pup mortality at the end of one year is about 35%. Males live at least 23 years and females to at least 26 years (Reijnders et al 1993, Childerhouse 2007). The average age of reproductive females is 10.75 yrs (Childerhouse 2007).

The breeding season for the New Zealand Sea Lion begins in late November when adult males return and establish themselves on territories through displays, vocalizing, and fighting. Adult females arrive in early December and give birth on average within 2.1 days after returning to the rookery (Chilvers et al. 2006). Males may have as many as 25 females within their territories. The bulls are frequently challenged by newly arriving males and neighbors, and turn-over of males is a regular occurrence. Many territorial bulls depart in mid-January with the end of the pupping period (Robertson et al. 2005).

The onset of estrous occurs 7-10 days after a female gives birth. Prior to this, the mother continuously attends her newborn pup. Following mating, females begin a phase of short foraging trips followed by pup attendance, typical of many otariids. Foraging trips average 2.7 days and are followed by 1.5 days of pup attendance and feeding ashore (Chilvers et al 2005). Also typical of many otariids, pups gather into groups while their mothers are away. Females and pups recognize each other through vocalizations and scent, and a small percentage of females will allow additional pups to nurse along with their own pup, which is unusual behavior for a pinniped. Pups are weaned at approximately 10 months. The primary causes of pup deaths within their first two months of life are trauma (35%), bacterial infections (24%), hookworm infection (13%), starvation (13%), and stillbirth (4%) (Castinel et al. 2007). Adult males are a significant source of mortality to pups, occasionally killing them outright and also through incidents of cannibalism. Pups are also trampled and killed by adult males challenging other males during territorial disputes.

New Zealand Sea Lions do not appear to be migratory, although they disperse widely over their range during the non-breeding season (Robertson et al. 2005). Some animals can be found at the major rookeries and haul-outs year-round. At sea they are active divers that forage on both benthic and pelagic prey. Mean dives for female New Zealand Sea Lions are to 129 m and mean dive duration is 3.9 minutes. Maximum dive depths are over 600 m and dives have been recorded to last as long as 14.5 minutes (Chilvers et al. 2006a).

New Zealand Sea Lions take a wide variety of vertebrate and invertebrate prey. Frequently-taken species include: opalfish, octopus, munida, hoki, oblique-banded rattail fish, salps, squid and crustaceans. Prey is taken in both benthic and pelagic habitats. Antarctic, Subantarctic, and New Zealand Fur Seals are taken as prey by adult male sea lions. Penguins and sea lion pups are also occasionally taken.

Predators include sharks, Leopard Seals, and presumably Killer Whales. Pups are also cannibalized by adult males of their own species.
Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): New Zealand Sea Lions were once more abundant, with a much more extensive range that included the North and South islands of New Zealand. The Maori people of New Zealand have traditionally hunted sea lions, presumably since first contact, as did Europeans upon their arrival much later. Commercial sealing in the early 19th century decimated the population in the Auckland Islands, but despite this, continued until the mid-20th century, when it was halted. The population may not have fully recovered from this period of overexploitation, although estimates of pre-exploitation population size are difficult to derive.

New Zealand Sea Lions have a highly restricted distribution, a small population, and most of the breeding activity is concentrated in two island groups in New Zealand's sub-Antarctic. This combination makes them vulnerable to disease outbreaks, environmental change, and human activities.

Commercial squid fishing near the two largest rookeries reported their first sea lion bycatch mortalities in 1978. In 1982, the fishery was moved at least 12 nautical miles away from the islands. However, this did not end mortality which from 1988 to 2007 ranged from 17-132 seals taken annually (Wilkinson et al. 2003, Chilvers 2008). Apart from direct mortality there is also the potential for prey competition and habitat modification from the fishing industry in the habitat of the New Zealand Sea Lion's breeding areas. Tourism at mainland sites and remote subantarctic islands can cause disruption to haul-out patterns and breeding activities.

Epizootic disease outbreaks at the Auckland Islands in 1998, 2002 and 2003 led to more than 50%, 33% and 21% early pup mortality respectively, and also led to mortalities of an unknown number of animals from other age classes during 1998. The source of the suspected bacterial agent and cause of the outbreak and subsequent mortality for the 1998 outbreak is unknown, however, the 2002 and 2003 outbreaks have been identified as cause by Klebsiella pneumoniae (Castinel et al. 2007).

Conservation Actions [top]

Conservation Actions: The New Zealand government has provided protection to New Zealand Sea Lions with laws that date back to 1881. The Marine Mammal Protection Act of 1978 provided additional measures. The squid fishery responsible for the by-catch of sea lions was moved away from the main colonies in 1982 when the government established a 12 nautical mile exclusion zone around the islands (Wilkinson et al. 2003) and later management plans set maximum levels of fishing related mortalities, which, when exceeded, led to the early withdrawal of the fishery. Sea Lion escape devices (SLEDs) have also been mandated in the fishery. Some concerns remain regarding the health of the sea lions expelled from these devices. The uninhabited Auckland Fauna Reserve forms part of the habitat of New Zealand Sea Lions (Reijnders et al 1993). Tourism is regulated on islands and at some mainland beaches on the South Island. Given the recent steady decrease in pup production at the Auckland Islands, and the uncertainty about the influence of human activities on this trend, it is unknown if the current conservation measures are sufficient to protect the species.

Bibliography [top]

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Campbell, R. A., Chilvers, B, L., Childerhouse, S. and Gales, N. J. 2006. Conservation management issues and status of the New Zealand (Phocarctos hookeri) and Australian (Neophoca cinerea) sea lions. In: A. W. Trites, D. P. DeMaster, L. W. Fritz, L.D. Gelatt, L. D. Rea and K. M. Wynne. (eds), Sea Lions of the World, pp. 455-471. Lowell Wakefield Fish Symposium, Alaska., USA.

Castinel, A., Duignan, P. J., Pomroy, W. E., Lopez-Villalobos, N., Gibbs, N. J., Chilvers, B. L. and Wilkinson, I. 2007. Neonatal mortality in New Zealand sea lions (Phocarctos hookeri) at Sandy Bay, Enderby Island, Auckland Islands from 1998 to 2005. Journal of Wildlife Diseases 43: 461-474.

Castinel, A., Grinberg, A., Pattison, R., Pomroy, B., Rogers, L. and Wilkinson, I. 2007. Characterization of Klebsiella pneumoniae isolates from NZ sea lions (Phocarctos hookeri) pups during and after the epidemics on Enderby Island, Auckland Islands. Veterinary Microbiology 122: 178-184.

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Robertson, B. C., Chilvers, B. L., Duignan, P. J., Wilkinson, I. S. and Gemmell, N. J. 2005. Dispersal of breeding, adult male Phocarctos hookeri: implications for disease transmission, population management and species recovery. Conservation Biology 127: 227?236.

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Citation: Gales, N. (IUCN SSC Pinniped Specialist Group) 2008. Phocarctos hookeri. In: The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 23 September 2014.
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