Phocarctos hookeri 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Carnivora Otariidae

Scientific Name: Phocarctos hookeri (Gray, 1844)
Common Name(s):
English New Zealand Sea Lion, Hooker's Sealion, Hooker's Sea Lion, New Zealand Sealion
Arctocephalus hookeri Gray, 1844
Taxonomic Notes:

The taxonomy of sea lions in New Zealand (Phocarctos) and Australia (Neophoca) was confused until it was resolved in a paper by King (1960).

Assessment Information [top]

Red List Category & Criteria: Endangered A4bd ver 3.1
Year Published: 2015
Date Assessed: 2014-11-18
Assessor(s): Chilvers, B.L.
Reviewer(s): Goldsworthy, S.D.
Contributor(s): Gales, N.J.
Facilitator/Compiler(s): Lowry, L., Chiozza, F., Ahonen, H. & Battistoni, A.
The New Zealand Sea Lion population is significantly reduced in size from historical levels and is projected to continue declining in the future. Threats to New Zealand Sea Lions have been identified (fishing related mortality, climate/nutritional stress, disease), they are not fully understood (Roberts and Doonan 2014). Management measures have been introduced to mitigate fisheries interactions, but declines in Sea Lion numbers have not ceased. The generation time is estimated to be 10.75 years with three generations being equivalent to approximately 32 years. Projecting the pup estimate from 1997/98 (3,021) at the Auckland Islands for three generations forward with a decline of 4%/year, the number of pups born in 2029/30 is estimated to be 840, which is a 72% reduction meeting the category Endangered under criterion A4bd. A population viability analysis (PVA) has also been carried out on the largest population (in the Aukland Islands), which predicts a 98% probability of extinction of this population within five generations (calculation based on model used in Chilvers 2012b).
Previously published Red List assessments:

Geographic Range [top]

Range Description:New Zealand Sea Lions have a highly restricted distribution for a marine mammal. Their primary habitat is several subantarctic islands south of New Zealand, and their surrounding waters. The principal breeding colony is at the Auckland Islands, with the most of the remaining animals breeding at Campbell Island (Maloney et al. 2012). 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 some births (McConkey et al. 2002). However, most of the animals hauling out on the South Island are males ranging in age from 2 to 11 years old. Wandering New Zealand Sea Lions also reach Macquarie Island. Before human occupation (Maori and European), New Zealand Sea Lions had a more extensive range that appears to have included most of the New Zealand mainland and subantarctic islands. Polynesian midden records show pup and adult bones from the top of the North Island, through the South Island and into the subantarctic islands of New Zealand (Childerhouse and Gales 1998).
Countries occurrence:
Australia (Macquarie Is.); New Zealand (South Is.)
FAO Marine Fishing Areas:
Pacific – southwest
Additional data:
Estimated area of occupancy (AOO) - km2:882408Continuing decline in area of occupancy (AOO):No
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:939120
Continuing decline in extent of occurrence (EOO):NoExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):500Lower depth limit (metres):700
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Counts of pups are commonly used as an index of abundance for pinniped populations (Berkson and DeMaster 2011). New Zealand Sea Lion pups are estimated to account for ~65% of the total number of mature females, and additional to this it has been estimated that 20% of all mature females will never breed (Chilvers et al. 2010). Using those assumptions, in 2008-09 New Zealand Sea Lions numbered approximately 9,880 (95% CI, 8,604–11,297; Geschke and Chilvers 2009) based on total pup production of 2,084, with the number of mature individuals estimated as less than 3,000 (Baker et al. 2010). Using 2013/14 data indicating total pup production of 2,189, the number of mature individuals is estimated to be 3,031 (Chilvers, unpublished). There is no historical population estimate but it is assumed that they were more abundant in the past due to the more extensive range they occupied (Childerhouse and Gales 1998).

The majority of pups are born at the Auckland Islands and annual pup production estimates have been made there since 1994/95 (pups are mostly born in December-January). Estimates suggest that the population was largely stable until 1997/98, but has declined since then at a rate of 4%/year (see the Table 1 in the Supplementary Material - see below). The number of pups counted in 2013/14 was 18% less than in 2012/13, and 48% less than 1997/98 (Childerhouse 2014). The decrease in pup production at Auckland Islands has been linked with decreasing numbers of adult females (Chilvers 2012a).

The other location where a substantial number of pups are born is Campbell Island. While there have been some counts made there (Childerhouse et al. 2005; Maloney et al. 2009, 2012; see Table 1) effort has been intermittent with significantly varying methods (including timing of surveys) and the data cannot be used to estimate meaningful trends. Therefore, while pup count results indicate that Sea Lions on Campbell Island are not in decline, the apparent upward trend is not predicted to continue (Maloney et al. 2012). Campbell Island is at the southern limit of the New Zealand Sea Lion range and pup mortality is very high there, apparently due to cold and wet conditions during the pupping season and substrates unsuitable for a breeding colony and early pup survival (Maloney et al. 2012).

A few pups are also born on the south coast of the South Island of New Zealand and on Stewart Island not far offshore (see Table 1 in the Supplementary Material - see below). The pups born at Stewart Island were only discovered in 2010/2011 and since that year regular searches of the most likely places Sea Lions would pup have been undertaken. The apparent increasing trend of Stewart Island pup counts (see Table 1 in the Supplementary Material - see below) is an artefact of better search techniques and areas searched on Stewart Island since 2010/2011 rather than an increase in pup numbers. The number of pups born at those locations has been about 30/year, which is less than 1% of the total pup production.

The mean age of reproduction for female New Zealand Sea Lions is 10.75 years (Childerhouse 2007) hence the generation time is estimated to be 10.75 years with 3 generations being equivalent to approximately 32 years.

The best information that can be used to project future abundance of New Zealand Sea Lions is the trend in pup production at the Auckland Islands. If the pup estimate from 1997/98 (3,021) is projected three generations forward with a decline of 4%/year the number of pups born in 2029/30 is estimated to be 840, which is a 72% reduction. While threats to New Zealand Sea Lions have been identified (fishing related mortality, climate/nutritional stress, disease), they are not fully understood (Roberts and Doonan 2014). Management measures have been introduced to mitigate fisheries interactions, but declines in Sea Lion numbers have not ceased.

A population viability analysis has been undertaken for the Auckland Island population of New Zealand sea lions (Chilvers 2012b). The PVA was only for this population because it makes up three-quarters of the species and has the most reliable population parameter estimates for modelling. The results show that at the current rate of decline in the Auckland Island population, this population could be functionally extinct (less than 1,000 animals within the population) by 2035 (24 years, less than three New Zealand Sea Lion generations). The modelling of the severest known fisheries and bacterial impacts shows that with a probability of 0.982, the Auckland Island population will be functionally extinct in 59 years with a mean annual population decline rate (r) of -0.039 (Chilvers 2012b).

Recent demographic assessment of the decline in the Auckland Island subpopulation has identified the main proximate causes for decline that include generally low pupping rates, declining trends in cohort survival to age 2 since the early 1990s, and low adult survival (age 6-14 years) since 1999 which may account for declining pup numbers at Sandy since the late 1990s (Roberts et al. 2014). Analyses to identify the ultimate causes have been compromised by a short time series mostly covering the period of decline (Roberts and Doonan 2014). However, juvenile (2-5 years) and adult (6-14 years) survival was poorly correlated to estimated fishing related mortality in the squid trawl fishery at the Auckland Islands. Correlative assessment with cohort survival to age 2 was consistent with disease-related mortality impacting survival after 2005. Roberts and Doonan (2014) consider that declines in maternal conditions, variable diet composition, changes in milk quality and pup mass, and reduced pupping rates are consistent with changes in the nutritional status of the subpopulation; however they noted that some of these responses could also occur in response to pup mortality not driven by nutritional stress factors.

See the Supplementary Material for further information about New Zealand Sea Lion pup production at Auckland Islands, Campbell Island, Otago Peninsula and Catlins (mainland New Zealand), and Stewart Island.
For further information about this species, see 17026_Phocarctos_hookeri_2015.pdf.
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Current Population Trend:Decreasing
Additional data:
Number of mature individuals:3031Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:No
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes

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 2.1-2.7 m long and may weigh 300-450 kg (Geschke and Chilvers 2009).  Adult females are 1.8-2.0 m long and weigh 90-165 kg (Chilvers et al. 2005). Newborns are approximately 70-100 cm long and weigh 8-10 kg (Chilvers et al. 2006a).  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 two months old and at the end of the molt look like adult females.

Males become sexually mature at the age of five years. The age of maturity for females is 3-4 years. The average estimated reproductive rate of adult female New Zealand Sea Lions is 65% per year (Chilvers et al. 2010). Pup mortality at the end of one year was 30-55% for the Auckland Islands area (Chilvers and MacKenzie 2010), and pup mortality was 55% for the first 6 weeks after birth at Campbell Island (Maloney et al. 2012). Males live at least 23 years and females to at least 26 years (Reijnders et al. 1993, 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. 2006b). Males may have as many as 25 females within their territories. The bulls are frequently challenged by newly arriving males and neighbours, and turn-over of males is a regular occurrence. Many territorial bulls depart the rookery in mid-January with the end of the pupping period (Robertson et al. 2006).

The onset of oestrous occurs 7-10 days after a female gives birth. Prior to this, females continuously attend their 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). Pups gather into groups while their mothers are away. Pups are weaned at approximately 10 months. The primary causes of pup deaths within the first two months of life are trauma (35%), bacterial infections (24%), hookworm infection (13%), starvation (13%), and stillbirth (4%; Castinel et al. 2007a). Adult males are a source of mortality to pups, occasionally trampling them during territorial disputes and also through incidents of cannibalism.

New Zealand Sea Lions are not migratory, although males disperse widely over their range during the non-breeding season (Robertson et al. 2006). Some animals can be found at the major rookeries and haulouts year-round. At sea they are active divers that forage on both benthic and pelagic prey. Individual New Zealand Sea Lions have been found to have two distinct dive profile types or foraging patterns: a benthic diving profile and a deeper, more varied meso-pelagic diving profile (Chilvers and Wilkinson 2009). Mean dive depths 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. 2006b). Mean total travel distances during foraging trips for lactating females are 423 km (SE = 43.9, max. = 1,087, n = 183). Satellite tracking data collected from 59 female New Zealand Sea Lions from all breeding sites at the Auckland Islands, indicates that they forage over the entire Auckland Island shelf, with extensive overlap with subantarctic trawl fisheries (Chilvers 2008, 2009; Chilvers et al. 2011).

New Zealand Sea Lions eat a wide variety of vertebrate and invertebrate prey. Frequently eaten species include Opalfish, Munida, Hoki, Oblique-banded Rattail, salps, octopus, squid, and crustaceans (Childerhouse et al. 2001; Meyneir et al. 2010). Antarctic, Subantarctic, and New Zealand Fur Seal pups and juveniles are taken as prey by adult male Sea Lions. Penguins are also occasionally taken (Lalas et al. 2007).

Great White Sharks are the only known predator of New Zealand Sea Lions (Robertson and Chilvers 2011).
Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:No
Generation Length (years):10.75
Movement patterns:Not a Migrant
Congregatory:Congregatory (and dispersive)

Use and Trade [top]

Use and Trade: 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 the depletion sealing continued until the mid-20th century when it was halted.

Threats [top]

Major Threat(s): Commercial sealing in the early 19th century decimated the New Zealand Sea Lion population in the Auckland Islands, but despite the depletion sealing continued until the mid-20th century. The population has yet to fully recover from the period of overexploitation (Childerhouse and Gales 1998).

At the present time, New Zealand Sea Lions have a highly restricted distribution, a small population, and nearly all of the breeding activity is concentrated in two subantarctic island groups. This restricted and small breeding population in combination makes them vulnerable to disease outbreaks, environmental change, and human activities.

The commercial Arrow Squid trawl fishery near the Auckland Islands reported their first New Zealand Sea Lion bycatch mortalities in 1978.  Reported or estimated mortality between 1995 and 2007 averaged 92 animals annually (range 17-143) which was 3.7% of the estimated number of mature individuals in the Auckland Island area (Thompson and Abraham 2009). Of particular concern is that most bycatch animals are females (up to 91%; Chilvers 2008). New Zealand Sea Lions are also incidentally caught in other trawl fisheries around the Auckland and Campbell Islands (Chilvers 2008, Thompson et al. 2013). Apart from direct mortality, competition and habitat modification caused by fishing activity may also be impacting New Zealand Sea Lion foraging areas (Robertson and Chilvers 2011).

Epizootic outbreaks at the Auckland Islands in 1998, 2002, and 2003 led to more than 50%, 33%, and 21% early pup mortality respectively, and were also responsible for the deaths of some 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 are unknown, however the 2002 and 2003 outbreaks have been identified as being caused by Klebsiella pneumoniae (Castinel et al. 2007b).

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 added additional measures, stating that no marine mammal could be caught, killed, injured, attracted, poisoned, tranquillized, herded, harassed, disturbed, or possessed. However, those measures do not afford protection from incidental captures in commercial fisheries if they are reported to the appropriate officials as required. 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. Due to the declining population, the New Zealand Sea Lion was listed as a Nationally Critical New Zealand Species in 2010 under the New Zealand threat classification system (Baker et al. 2010, Townsend et al. 2008).

There are three main management strategies currently in place to mitigate New Zealand Sea Lion bycatch interactions in trawl fisheries off the Auckland Islands:

1) Input controls: a Marine Mammal Sanctuary and Marine Reserve surrounding the Auckland Islands extending 22.2 km offshore, within which no trawling or any other form of fishing is allowed. However, satellite tracking data indicate that this closure only protects a small part of the foraging areas of adult females (Chilvers et al. 2005, Chilvers 2009).

2) Output controls: restrict the number of New Zealand Sea Lions the trawl fishery may kill incidentally within designated fishery management zones before the zone is closed for the season (Chilvers 2008).

3) Sea Lion exclusion devices (SLEDs): SLEDs were introduced to the fishery in 2001. A SLED is a metal grid fixed inside the trawl net that allows smaller objects, such as squid, to pass into the cod-end, while larger objects are directed to an escape hatch opening. There is uncertainty about the efficacy of SLEDs and the overall impact of fishery interactions on New Zealand Sea Lion populations.

Citation: Chilvers, B.L. 2015. Phocarctos hookeri. The IUCN Red List of Threatened Species 2015: e.T17026A1306343. . Downloaded on 24 September 2018.
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