The New Zealand sea lion (Phocarctos hookeri), also called Hooker's sea lion, is known as pakake (for both males and females), whakahao (male), and kake (female) in Māori. This species is found only in New Zealand and mainly breeds on the subantarctic Auckland and Campbell islands. In recent years, the sea lions have slowly increased their numbers and returned to areas along the coasts of New Zealand's South and Stewart islands. There are about 12,000 New Zealand sea lions, making them one of the rarest sea lion species in the world. They are the only species in the genus Phocarctos.
Physiology and behaviour
New Zealand sea lions are one of the largest animals in New Zealand. Like all otariids, they show big differences between males and females. Adult males are 240–350 centimetres (7.9–11.5 ft) long and weigh 320–450 kilograms (710–990 lb), while adult females are 180–200 centimetres (5.9–6.6 ft) long and weigh 90–160 kilograms (200–350 lb). When born, pups are 70–100 centimetres (2.3–3.3 ft) long and weigh 8–10 kilograms (18–22 lb). Baby sea lions have a thick coat of dark brown hair that changes to dark gray with cream markings on the head, nose, tail, and near the flippers. Adult females have coats that range from buff to creamy gray, with darker coloring around the face and flippers. Adult males are blackish-brown and have a thick black mane of coarse hair that reaches their shoulders. New Zealand sea lions strongly return to the same place to breed.
The New Zealand sea lion’s behavior on land is different from other pinniped species. During the breeding season, female sea lions slowly move inland with their pups to protect them from male harassment, wind, storms, and possible infections. They can travel up to 2 kilometres (1.2 mi) inland, moving from sandy beaches to grassy areas and forests. They are the only pinniped species known to travel far inland, and they often choose forests as their habitat. As more sea lions have lived on the mainland since the 1990s, this behavior has caused them to enter human areas more often.
Distribution
The main places where New Zealand sea lions breed are the Auckland and Campbell Islands in the New Zealand subantarctic region. About 99% of all baby sea lions are born there each year. On the Auckland Islands, there are three active breeding areas. Most sea lion pups are born on Dundas Island. A smaller breeding area is located at Sandy Bay on Enderby Island, and the smallest breeding area is on Figure of Eight Island. A very small breeding area at South East Point on Auckland Island no longer seems to be used. The other major breeding area is the Campbell Islands.
In the past, New Zealand sea lions lived across mainland New Zealand and Stewart Island. However, they were no longer found in these areas because of hunting by humans. For the first time in more than 150 years, sea lions began breeding again on the South Island coast in 1993, on the Otago Peninsula after a female named Mum gave birth. Small groups of breeding sea lions have also started to appear in parts of Stewart Island and along the Catlins coast, south of the Clutha River.
Recent DNA studies show that the New Zealand sea lion is a group that was once only found in subantarctic regions. Between 1300 and 1500 AD, a different group of sea lions that lived on the mainland was wiped out by the first Maori settlers. Since then, the subantarctic group has gradually taken over the role that the mainland group once had. Evidence from ancient trash heaps and DNA suggests that a third group of sea lions became extinct at the Chatham Islands due to hunting by the Moriori people.
Diet and predation
New Zealand sea lions eat many different animals, including fish like Antarctic horsefish, red cod, opalfish, and Patagonian toothfish, as well as rays, sharks, squid, octopus, crustaceans, seabirds, other marine mammals, and even New Zealand fur seals. Research shows that where they live affects their diet. For example, sea lions at Otago Peninsula and Campbell Island, which are at the northern and southern ends of their breeding range, eat very different prey. New Zealand sea lions are also hunted by great white sharks. A study of adult sea lions at Sandy Bay, Enderby Island, found that 27% had scars from near-miss shark attacks.
Status
New Zealand sea lions are the most at-risk sea lion species in the world. The main group of sea lions that breed at the Auckland Islands has decreased by about 50% between 2000 and 2015. In 2013, the number of baby sea lions born on the Auckland Islands reached 1,931, up from 1,684 in 2012. This count includes both live and dead pups, as it helps scientists estimate the number of adult females that can breed, but not the number of future babies. The 2013 number was the highest in five years. The population on Campbell Island seems to be growing slowly, and about 30% of all births for the species happen there. The groups on Otago and Stewart Islands are small but are increasing slightly. Overall, the number of New Zealand sea lions dropped from about 15,000 in the mid-1990s to 9,000 in 2008, based on the number of pups born each year.
In 2010, the Department of Conservation, which is responsible for protecting marine mammals, changed the species’ status in New Zealand’s Threat Classification System from Nationally Endangered to Nationally Critical. The department estimates that the sea lions on the Auckland Islands, which make up nearly 80% of the total population, may become functionally extinct by 2035. However, the New Zealand Ministry for Primary Industries says the research used to make this prediction is of low quality and should not be used for management decisions. In 2015, the International Union for Conservation of Nature (IUCN) classified the species as "Endangered" due to its small total population, limited number of breeding groups, and the predicted decline of the Auckland Islands breeding population.
In 2019, the New Zealand sea lion’s status improved to "Nationally Vulnerable." The rate of population decline has slowed in most breeding areas, and Stewart Island was officially recognized as a new breeding colony in 2018. The species’ global IUCN status remains "Endangered."
Threats
Subsistence hunting and commercial harvesting of sea lions greatly reduced the breeding area and population of New Zealand sea lions between the 13th and 19th centuries. In 1893, laws were passed in New Zealand to stop sealing, which included hunting New Zealand sea lions and New Zealand fur seals. In their book The Animals of New Zealand, Frederick Hutton and James Drummond described the hunting of New Zealand sea lions.
In the 1990s, as squid fishing increased around the Auckland Islands, many sea lions were accidentally caught in fishing nets and drowned. The government uses a system to set a yearly limit for how many sea lions can be accidentally killed by fishing. If this limit is expected to be reached, the Minister of Primary Industries may close the fishery. The last time this limit was exceeded was in 2000, though several fishery closures happened in the 1990s.
In late February 2013, sea lion deaths were observed in the Auckland Island squid fishery for the first time in three years. Young sea lions slipped through a grid at the net’s opening into the cod end of the net. The grid, which is 23 cm wide, is designed to keep adult sea lions outside the net while allowing squid to pass through. In 2013, one adult female sea lion was accidentally caught.
In August 2013, the southern blue whiting fishery captured 21 male sea lions more than 100 km from the Campbell Islands. Four were released alive. No captures were reported the year before. The government asked the fishing vessels to use sea lion exclusion devices (SLEDs) to reduce accidental catches.
In 2014, the estimated number of sea lions accidentally caught was 11.58% of the yearly limit. More fishing vessels in the Auckland Island squid fishery now have government observers on board to report accidental catches directly, rather than relying on computer models. During the 2014 season, observers covered 84% of fishing trips. In that season, two sea lions were reported to have been accidentally caught.
In 2001, SLEDs were introduced into the Auckland Island squid fishery to reduce accidental sea lion catches. Conservation groups support SLED use to protect other marine animals, such as sharks. Since 2007, all vessels in the Auckland Islands fishery have used SLEDs. Some scientists believe sea lions do not survive interactions with SLEDs, but the Ministry for Primary Industries (MPI) states that fishing-related deaths have a small effect on the sea lion population. MPI estimates that sea lions have an 85% chance of escaping SLEDs and a 97% chance of surviving if they escape, though this estimate may be slightly too low.
Food availability is a major factor in population changes for pinniped species. The Auckland Islands population has shown signs of food shortages, including poor health in adult females, delayed reproduction, very low pup birth rates, low pup survival, and changes in diet. Starvation was the likely cause of death for 62% of pups studied at Campbell Island in 2015, when 58% of all pups born were estimated to have died within the first month of life.
Although the number of pups born in the Auckland Islands varies, a decline occurred after a bacterial disease caused by Campylobacter spread in 1998, killing about 53% of newborn pups and 20% of adult females. In 2002, another bacterial disease caused by Klebsiella pneumoniae killed 32% of pups, and in 2003, another 21% of pups. Since 2002, K. pneumoniae has caused many pup deaths at Enderby Island. Infected pups suffer from meningitis and sepsis. In March 2014, the Conservation Minister, Nick Smith, said that too much attention was being given to fishing-related deaths, and 300 pups had died the previous summer from an unknown disease.
The mainland population of New Zealand sea lions is expected to reach 1,000 by 2044, which may lead to challenges such as managing marine protected areas, fishing limits, and population control.
New Zealand sea lions may spread to areas across mainland New Zealand, but they face challenges with humans. Sea lions have been seen in residential areas, including backyards, homes, swimming pools, golf courses, playgrounds, and fish-and-chip shops. Female sea lions and pups have adapted to living in commercial pine plantations, which are privately owned. Roads and fences block their movement inland. Sea lions have been hit by cars, and some have been deliberately killed, harassed, or injured with clubs. Incidents involving domestic dogs have also been reported.
To protect New Zealand sea lions, the Department of Conservation works with local communities to raise awareness about the species’ return and behavior.