HOOKER'S (OR) NEW ZEALAND SEA LION

 

Male And Female

The New Zealand sea lion (Phocarctos hookeri), once known as Hooker's sea lion, and as pakake (for both male and female) or whakahao (male) and kake (female) in Māori, is a species of sea lion that is endemic to New Zealand and primarily breeds on New Zealand's sub Antarctic Auckland and Campbell islands, and have in recent years been slowly breeding and recolonizing around the coast of New Zealand's South and Stewart islands. The New Zealand sea lion numbers around 12,000 and is one of the world's rarest sea lion species. They are the only species of the genus Phocarctos.

Distinctive characteristics

New Zealand sea lions are one of the largest New Zealand animals. Like all otariids, they have marked sexual dimorphism; adult males are 240–350 centimeters (7.9–11.5 ft.) long and weigh 320–450 kilograms (710–990 lb.), while adult females are 180–200 centimeters (5.9–6.6 ft.) long and weigh 90–160 kilograms (200–350 lb.)At birth, pups are 70–100 centimeters (2.3–3.3 ft.) long and weigh 8–10 kilograms (18–22 lb.); the natal pelage is a thick coat of dark brown hair that becomes dark gray with cream markings on the top of the head, nose, tail and at the base of the flippers. Adult females' coats vary from buff to creamy grey with darker pigmentation around the muzzle and the flippers. Adult males are blackish-brown with a well-developed black mane of coarse hair reaching the shoulders. New Zealand sea lions are strongly philopatric.

The New Zealand sea lion's terrestrial behavior is unique among other pinniped species. In the breeding season, female New Zealand sea lions gradually move inland with their pups to protect them from harassment by males, wind, storms, and potential parasitic infections. They can move up to 2 kilometres (1.2 mi) inland, from sandy beaches to tall grasses, and into forests. They are the only pinniped species known to disperse far inland and have a preference for forests.

Dental Formula     I 3/2, C 1/1, PC 6/5.

Size

The maximum length of adult males is about 3.5 m and average weight is 450 kg. The maximum length for adult female is about 2 m and average weight is 160 kg. Pups are born at an average of about 1m and 8-10 kg.

Life Span    Male live up to 23 years old and female live up to 18 years old.

Gestation Period    335 days.

Can be confused with

Three fur seals (New Zealand, Antarctic, and sub-Antarctic) are known to occur in or near the present range of the New Zealand sea lion. New Zealand sea lions can be differentiated from all fur seals, based on a combination of features including coloration, fur characteristics, head and muzzle shape, size of the ear pinnae, and size and shape of the outer toes on the hind flippers.

Distribution

The main breeding populations are at the Auckland and Campbell Islands in the New Zealand sub Antarctic, where approximately 99% of the species' annual pup production occurs. There are currently three functioning breeding rookeries on the Auckland Islands. Most sea lions are born on Dundas Island. A smaller rookery exists at Sandy Bay on Ender by Island and the smallest rookery is on Figure of Eight Island. An even smaller rookery at South East Point on Auckland Island appears to now have been abandoned. The other major breeding area is the Campbell Islands.

Historically, New Zealand sea lions were distributed all over mainland New Zealand and Stewart Island, but were extirpated from these areas due to human hunting activities. For the first time in over 150 years, sea lions began breeding again on the South Island coast in 1993, on the Otago Peninsula after Mum gave birth. Other small populations of breeding sea lions have recently begun to establish in various parts of the Stewart Island coastline and have been observed on the Catlin’s coast south of the Clutha River.

Recent DNA information indicates the New Zealand sea lion is a lineage previously restricted to sub Antarctic regions. Somewhere between 1300 and 1500 AD, a genetically distinct mainland lineage was wiped out by the first Maori settlers, and the sub Antarctic lineage has since then gradually filled the ecological niche. It has been inferred from middens and ancient DNA that a third lineage was made extinct at the Chatham Islands due to predation by the Moriori people. 

Ecology and behavior

Female Hooker’s sea lions, Phocarctos hookeri, sexually mature at 3-4 years of age, males at 5 years, however males do not begin breeding until at least 8 years of age. Breeding season takes place between November and January. Pups are born measuring 70-100 cm in length, weighing 7.9 kg (female’s average 7.2 kg). Bulls begin arriving in November to fight for territory before the females arrive a few weeks later. Successful bulls establish territories consisting of between 8-25 females. The females give birth shortly after arriving, then mate a week to ten days later. Pups are born with a thick coat of light to dark brown fur. About 10-14 days after a pup is born, females return to sea to feed, then return to land for 2-3 days to nurse. This feeding cycle continues for about 8-12 months. At 2-3 weeks of age pups begin to swim. Adult males remain ashore and do not normally feed during breeding season. Molting follows breeding season in late February through to early May.

Predation

New Zealand sea lions are in turn preyed on by great white sharks and dogs on Main Island, with 27% showing evidence of scarring from near-miss shark attacks in an opportunistic study of adult New Zealand sea lions at Sandy Bay, Ender by Island. Humans also hunted New Zealand sea lions, but today New Zealand laws protect the species.

Feeding and prey

New Zealand sea lions are known to prey on a wide range of species including fish such as Antarctic horse fish and Patagonian tooth fish, cephalopods (e.g. New Zealand arrow squid and yellow octopus), crustaceans, seabirds and other marine mammals, and even New Zealand fur seals. Studies indicate a strong location effect on diet, with almost no overlap in prey species comparing sea lions at Otago Peninsula and Campbell Island, at the north and south extents of the species' breeding range. Migratory patterns of Hooker’s sea lions are not well known. They are opportunistic feeders with a diet of cephalopods, crabs, crayfish, and fish. Adult sea lions are able to dive repeatedly to 300 m and have been known to dive to over 600 m. They have been known to travel up to 130 km offshore during feeding trips. They will eat penguins and fur seals on occasion, and adult male Hooker’s sea lions have been observed feeding on sea lion pups. Great white sharks and orca (killer whales) prey on adults and pups.

Exploitation

The mainland population was estimated to reach 1000 animals by 2044, leading to issues of 'marine protected areas, local fishing quotas and numbers management'. New Zealand sea lions are projected to potentially distribute all around mainland New Zealand, but they face potential human conflicts, especially due to their unique inland movement behaviour. New Zealand sea lions have been hit by cars on roads, and deliberately killed, harassed, and clubbed. There have also been incidents of disturbance from domestic dogs. Infrastructure such as roads and fences also pose as barriers to their inland movement. Females and pups on the mainland have also adapted to commercial pine plantations, which are privately-owned lands. In order ensure the protection of New Zealand sea lions, the Department of Conservation works to engage with local communities and spread awareness on this species' recolonisation and behavior. 

 Threats and status

Hooker’s sea lions were hunted for their hide and oil until hunting was banned in New Zealand in 1893. The New Zealand (Hooker’s) sea lion was designated as a Threatened Species under New Zealand’s Marine Mammals Protection Act in August 1997, and is also listed as Vulnerable on the IUCN Red List. A 20 km Marine Mammal Sanctuary was established around the Auckland Islands that conservation groups hope to have extended to 100 km. New Zealand’s sub Antarctic islands were granted UNESCO “World Heritage” status in 1998.

A major threat to the species is entanglement in trawl fishing nets, particularly the squid trawl fishery. In recent years, squid trawling has been limited due to sea lion mortality. Unfortunately, the limits were exceeded between1995-1997 when an estimated >100 sea lions drowned annually in squid trawl nets. These limits have been enforced more strictly since then, and in 2000, the squid trawling season ended early when the number of sea lions killed reached the maximum of 65. Fishing devices that protect marine mammals are being designed and tested. The New Zealand Department of Conservation is developing a Population Management Plan for the species due to its status as a protected species.

The species is particularly vulnerable because of its limited breeding sites. In 1998 at least 1600, over 53% of the year’s pups, and many adults died of an unknown disease. High juvenile mortality has also been caused by pups getting caught in rabbit burrows, however the Department of Conservation has eliminated the rabbit population, a measure that reduced the problem significantly.

Factors hypothesized include

The direct and indirect effects of large-scale commercial fisheries on key prey species, long –term ecosystem shifts, and changes in behavior by a primary predator, the killer whale, or a combination of these factors.

IUCN status    Vulnerable     

 

Female With Pup