Phocarctos hookeri (Gray, 1844)
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publication ID |
https://doi.org/ 10.5281/zenodo.6604474 |
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DOI |
https://doi.org/10.5281/zenodo.6604528 |
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persistent identifier |
https://treatment.plazi.org/id/965C87FE-1E56-5644-992F-9B9F8644FA2A |
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treatment provided by |
Diego |
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scientific name |
Phocarctos hookeri |
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New Zealand Sea Lion
Phocarctos hookeri View in CoL
French: Otarie de Nouvelle-Zélande / German: Neuseeland-Seelowe / Spanish: Ledn marino de Nueva Zelanda
Other common names: Hooker's Sea Lion, Hooker's Sealion, New Zealand Sealion
Taxonomy. Arctocephalus hooker: Gray, 1844 ,
“Inhab. Falkland Islands and Cape Horn.” Corrected by J. W. Clark 1873 to “Auckland Islands. ..between 800 and 900 miles S. of Tasmania, in lat. 50°48’S, long. 166°42’E,” New Zealand.
This species is monotypic.
Distribution. S Pacific subantarctic, mainly the Auckland, Campbell, and Stewart Is and New Zealand’s South Island. View Figure
Descriptive notes. Total length 230-270 cm (males) and 180-200 cm (females); weight 320-450 kg (males) and 90-165 kg (females). Newborns are 70-100 cm and 8-10 kg. Dental formula 13/2, C 1/1, PC 6/5 (x 2) = 36. New Zealand Sea Lions are sturdily built and powerful. They display sexual dimorphism, with mature males reaching 1-2-1-5 times the length and 3—4 times the weight of mature females. Large head has broad muzzle that may be square or round at tip. Small ear pinnae are not prominent. Vibrissae are short-to-medium length, at times extending to pinnae. Males have sagittal crest on skull, but profile shows little forehead and may even appear convex because rounded crown slopes down to short muzzle. Females and subadults have flatter head silhouettes. Neck on adult males is extremely wide and muscular and accentuated by mane of long guard hairs. Females are stocky but lack large neck and mane. Foreflippers have some hair on dorsal surfaces, but hair does not extend to rounded tips. Otherwise, flippers, including undersides, are covered with dark leathery skin. First digit is the longest and curves back. Cartilaginous rods in hindflippers lengthen toes, and first and fifth digits are longer than three middle digits. Similar to foreflippers, hindflippers have hair on upper part closest to body but otherwise are covered in dark leathery skin. Adult female and young New Zealand Sea Lions are tan, cream, or gray on neck and back, with paler hues on chest and abdomen, although some females show little contrast above and below. Face often has pale areas above ears and eyes and along muzzle. Crown is darker. Males darken as they mature. Oneto three-year-old males are similar to females, although some may be pale ruddy brown. Four-year-olds are darker brown above, with paler hues on chest and abdomen, as they begin to develop muscular neck and shoulders and mane. Fiveand six-year-old males are entirely brownish-black, and some individuals of advanced age appear grizzled because they grow white hairs on mane. Newborn New Zealand Sea Lions are dark brown with pale coloration on head and neck. Young males are darker than female young. At two months of age, young molt into coat similar to females. Molts are annual forjuveniles and adults, occurring over a 2month period in December—June.
Habitat. Breeding sites on sandy beaches where young New Zealand Sea Lions are less likely to be injured if trampled by a territorial male. Adult females have an unusual habit of moving their young away from breeding beaches and then inland,as far as 1-5 km from the shoreline, to brushy or even forested habitat. Marine predators include sharks, Leopard Seals (Hydrurga leptonyx), and Killer Whales (Orcinus orca).
Food and Feeding. The diet of the New Zealand Sea Lion is varied and composed of bottom-dwelling and open-water species, including opalfish (Hemerocoetes monopterygius), munida (Munida gregaria), hoki (Macruronus novaezelandiae), rat-tail fish ( Macrouridae ), octopus, squid, salps ( Salpidae ), and crustaceans. Males may also prey on New Zealand Fur Seals and penguins and have been known to cannibalize young.
Breeding. Unlike the Australian Sea Lion ( Neophoca cinerea ), the New Zealand Sea Lion have a polygynous breeding system with general features like those of fur seals ( Arctocephalus spp. ). Males hold territories on shore and fight, vocalize, and make postural displays to maintain them. Mature males arrive first at a breeding rookery to establish a territory, followed by pregnant females. More than one female will select a male’s territory, and each will give birth to a single neonate soon after arriving there. Non-breeding subadult males, referred to as bachelors, congregate outside territories at edges of rookeries. Breeding males remain ashore continuously. A few days after parturition, a female leaves her neonate to go on a foraging trip at sea. Young are alone, or join a group of other unattended neonates. Males take no role in parenting. Territorial males may pose a threat to young, sometimes trampling or attacking them, but their presence can benefit young by keeping bachelors at bay and reducing crowding in the territory. After a female’s milk stores are replenished, she returns to the rookery, attracting her young with a special high-pitched call. This pattern of nursing bouts and foraging trips repeats until the offspring is weaned at 10-12 months of age, although females may extend care for another year or more. Foraging trips tend to be short when offspring are young and become longeras they get older. Older offspring and juveniles may make foraging trips with their mothers. Soon after she gives birth, the female enters estrus and usually copulates with the male in whose territory she resides. Thus, females are likely to be pregnant and lactating throughout most of their life as an adult. After conception, development ofthe fertilized egg is suspended at the blastocyst stage and then resumes a few months after implanting in the uterus. This delayed implantation allows gestation of only 8-9 months to synchronize to an annual breeding cycle. For New Zealand Sea Lions, the breeding season is in November—]January. Males arrive at the rookery in November, and pregnant females arrive in early December;territories may have up to 25 females. Females are sexually mature at 3—4 years old, and average age of breeding females is 10-7 years. Females bear young 2-1 days after arriving and then enter estrus 7-10 days later. After copulating, females begin feeding trips that average 2-7 days, followed by a nursing bout of 1-5 days. Unusual for pinnipeds, some lactating females will allow an offspring of another female to nurse alongside her offspring. Male New Zealand Sea Lions abandon the rookery by mid-January, at which time females move with their young away from the rookery, then inland to vegetated habitat to avoid attention from the remaining males. In addition to being killed by males, young also suffer from bacterial infection, hookworms, and starvation, resulting in an annual mortality rate of ¢.35%. Life span is 23 years or more for males and 26 years or more for females.
Activity patterns. At sea, New Zealand Sea Lions dive energetically, are among the deepest-diving sea lions, and frequently feed on benthic prey. Typical dives reach depths of 129 m and last for 3-9 minutes. Maximum dives are more than 600 m and last up to 14-5 minutes.
Movements, Home range and Social organization. New Zealand Sea Lions are nonmigratory. They will spread out to sea after the breeding season, but some individuals can be found at major colonies throughout the year. After territorial males begin to depart the rookery, females and young depart to avoid aggressive non-territorial males that attempt to mate with females and can attack young. This often requires the young to swim with its mother from its natal site to another island with suitable habitat. New Zealand Sea Lions will wander outside their primary distribution and have been seen at Macquarie Island.
Status and Conservation. Classified as Vulnerable on The IUCN Red List. Total population of the New Zealand Sea Lion is ¢.11,900 individuals. It was more abundant historically, with a distribution that included both the North Island and South Island of New Zealand. It has endured hunting pressure beginning with the Maori people, followed by European sealers in the 19" century. Despite nearly exterminating the population of New Zealand Sea Lions at the Auckland Islands, commercial hunting did not end until the mid-20" century. New Zealand Sea Lions are restricted to just a few isolated breeding islands, and small numbers breed on the south-eastern coast of the South Island of New Zealand. Birth rates have declined since 1997 for unknown reasons, although contributing factors may be mortality as bycatch in fisheries and disease. The squid fishery near the Auckland Islands resulted in the deaths of 1-2% of adult females annually. Despite stricter management of the operations, including sea lion escape features required in the trawl nets, 17-132 New Zealand Sea Lions were killed each year in 1988-2007. Young also suffered three unusual mortality events in 1998, 2002, and 2003 that were caused by bacterial infections. Infections may have been exacerbated by stresses associated with prey shortages due to El Nino weather patterns. New Zealand Sea lions recolonizing the South Island have experienced conflicts with humans because females with young relocate from shoreline rookeries up to 1-5 km inland, and some males travel 0-5 km from the shoreline. There they encounter a human-altered environment with buildings, sports fields, campgrounds, and gardens. Several New Zealand Sea Lions have been hit by motor vehicles as they crossed roads. These inland movements will need to be considered when drafting protective legislation and designing conservation areas.
Bibliography. Augé, Chilvers, Mathieu & Moore (2012), Augé, Chilvers, Moore et al. (2009), Baker et al. (2010), Beentjes (1989), Breen et al. (2003), Campbell et al. (2006), Castinel et al. (2007), Childerhouse & Gales (1998), Childerhouse et al. (2010), Chilvers (2008, 2012), Chilvers & Wilkinson (2008), Chilvers, Amey et al. (2011), Chilvers, Robertson, Wilkinson & Duignan (2007), Chilvers, Robertson, Wilkinson, Duignan & Gemmell (2005), Chilvers, Wilkinson & Childerhouse (2007), Chilvers, Wilkinson, Duignan & Gemmell (2005, 2006), Clark (1873), Costa & Gales (2000), Gales (2008, 2009), Gales & Fletcher (1999), Jefferson et al. (2008), McConkey et al. (2002), Meynier et al. (2009), Reijnders et al. (1993), Rice (1998), Robertson & Chilvers (2011), Robertson et al. (2005), Walker & Ling (1981a), Wilkinson et al. (2000).
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