Female New Zealand sea lion, Auckland
The New Zealand sea lion (Phocarctos hookeri - formerly known as the Hooker's sea lion) has a blunt nose and short whiskers.
There is a marked difference in appearance between adult males and females.
Mature males are brown to black in colour with well-developed manes reaching to the shoulders.
Females are lighter in colour, predominantly creamy grey with darker pigmentation around their flippers.
- Adult females: length 1.6-2.0 m, weight 100-160 kg
- Adult males: length 2.4-3.5 m, weight 250-400 kg.
Pups of both sexes are chocolate brown with paler areas around the head. Juvenile males can resemble adult females in colour and size.
Archaeological evidence suggests that NZ sea lions used to be found along the entire length of the NZ coast from the north of the North Island down to Stewart Island and the sub-Antarctic Islands. The finding of sea lion remains in excavations and historical records indicate that both Mäori and European settlers hunted sea lions.
Nowadays NZ sea lions breeding colonies are only found in the Auckland and Campbell Islands (North West Bay of Campbell Island). 79% of the species’ pups are born in three islands of the Auckland Islands (Dundas, Enderby and Figure of Eight). The Auckland Islands sea lion colonies are nevertheless a remnant of what used to be once before the island’s discovery in 1806. Soon after sea lions were exploited for their pelts for a period of 24 years until activities ceased due to the low numbers of animals remaining. It is evident that many New Zealand sea lions were killed during this time but it is unknown exactly how many due to poor and often non-existent record keeping. Occasional killings continued until the late 1880's when the animals were protected by law.
In 1993 a single female, born at the Auckland Island, started to breed on the Otago peninsula. Since 1993 32 pups have been born at the Otago peninsular with the original females daughter, grand daughters and great-grand daughters now breeding there.
Haul-out sites are more widespread and extend to Macquarie Island in the south to Stewart Island and the islands of Foveaux Strait.
Sea lions favour sandy beaches as haul-out areas. On warm summer days they will flick sand over themselves to try to keep cool. Females with pups will often move well inland on islands using vegetation or forest for shelter.
Recent population estimates set the total population lower than 10,000 and declining. This makes the New Zealand sea lion the rarest sea lion species. Apart from the Australian sea lion and all other sea lion species are in the 100s of thousands!
Diet and foraging
New Zealand sea lion prey on a wide variety of species. Squid have been shown to be an important dietary component for New Zealand sea lions in the sub-Antarctics but not for those in the mainland region. Other prey species include fish, some sharks and rays, octopus and various other invertebrates.
New Zealand sea lions have also been reported to occasionally prey upon fur seals, elephant seals, penguins and various sea birds.
Female New Zealand sea lions may travel up to 175 km from the coast to feed. Dives may be up to 700 m in depth, though most are less than 200 m and last four or five minutes.
Diving is almost continuous when at sea with females diving deeper, longer and covering a greater area and distance in a single foraging trip than any other fur seal or sea lion species.
Research indicates that New Zealand sea lions on the Auckland Islands may be operating at their physiological limits when foraging. This limits the population’s ability to sustain any other human or environmental impacts.
Females mature as early as 3 years old, giving birth for the first time at 4. Males are able to hold a territory at 8-9 years old. Life expectancy is less clear, the oldest known female is 21years old but some research carried out has shown maximum ages of 23 years for males and females.
Breeding occurs over the summer months. Mature males are highly territorial and aggressive in their defence. On the Auckland Islands males occupy a beach in late November and pregnant females congregate at nearby haul-outs. Several days prior to giving birth to a single pup, females move to the breeding beach.
Females form into harems of up to 25 and are attended by a single dominant bull. Challenger and bachelor bulls remain around the periphery and occasionally challenge the dominant bull.
Females give birth to a single pup every 1-2 years. Pupping begins in the second week of December and ceases by the second week in January at which time the remaining bulls disperse and the harems break-up. Pups are born on the beach but are moved by their mothers to nearby vegetation after about six weeks.
The females then spend the next year alternating between foraging trips to sea and periods on land suckling their pups. Pups form pods near the periphery of harems while their mothers are at sea for warmth and protection.
Pups are dependent on their mothers for milk and protection for the first year of their lives. While mothers are at sea feeding, pups are alone. This is natural but they are particularly vulnerable to disturbance during these periods, so please keep your distance.
Sharks are the New Zealand sea lions most likely predators. This is based on presence of wounds consistent with these predators. Pups are most vulnerable and it is also known that on occasions pups have been attacked by adult males of their own species.
Moving Gem: A sea lion translocation tale - Conservation blog 26 January 2012