The New Zealand Sea Lion (Phocarctos hookeri) is endemic to New Zealand, specifically the subantarctic islands. The species is also sometimes known as Hooker’s Sea Lion, after Sir Joseph Hooker, a British botanist who explored the islands in 1844. Probably the rarest Sea Lion in the world, P. hookeri are classified as Endangered by the IUCN. Estimated population size = 9,880.

P. hookeri are a very large and robust eared seal, which may even exceed the Steller Sea Lion in length, just not bulk (males ♂ up to 3.5 m long/ 450 kg, females ♀ up to 2 m/ 230 kg). Sexual dimorphism is immediately apparent, and the males have heavy muzzles with huge heads and a striking mane and crown, whilst the females have narrower heads and smaller muzzles. Flippers in both are slender. Fur of the male seals is usually dark brown to blackish, while in the females it is generally light brown or buff, even sometimes yellowish. The crowns of the males are distinctively paler than the rest of their coat, and similarly, there is a contrast between the dorsal and underside of the female coat, though here the lighter shade is underneath.

Feeding behaviour:

P. hookeri are competent divers, foraging both in the benthos on deep dives (over 600 m) and in the water column, remaining underwater for up to 15 minutes. They will take on a variety of vertebrate and invertebrate prey. Species identified in the diet include duckbills, hake, flounder, squat lobsters, octopus, squid and crustaceans, and also the occasional penguin. Like the Steller Sea Lion, they may also take juvenile fur seals of various species (Antarctic, Subantarctic and New Zealand). Diet is fairly specific to the exact location of the individual.

Breeding behaviour:

Sexual maturity – males ♂ 5 years old/ females ♀ 3-4 years old.

In late November, male P. hookeri arrive at the breeding rookeries, displaying and fighting to obtain their territories, which come December, may contain up to 25 females each. Mating in this polygynous society takes place on the beach or surf zone, and after a gestation of around a year, pups are born from December to January. These pups are born with a thick, warm, dark brown lanugo, which has lighter patches on the crown and muzzle. Female pups are paler than male pups. For a week or two, the mother remains with her pup, before beginning to venture out on gradually increasing foraging trips at sea. During these trips, the pups will often gather together into groups on shore. By a month old they might start to explore freshwater pools. Weaning occurs at around 9-10 months. Moult for P. hookeri occurs after the pupping season and depends on age, with youngsters moulting earlier than mature males. P. hookeri tend to live into their mid-twenties, with females averaging a little older than males.

There are no subspecies of P. hookeri.

Photos: Simon Childerhouse (top) and Laureline Meynier