(Gray, 1844) - Hooker's sea lion
Distinctive Characteristics
Hooker's sea lions have a muzzle that is fairly broad; the top is either flat or slightly rounded. The ear pinnae are small and inconspicuous. The vibrissae are moderate in length, reaching as far back as the pinnae on some animals. In adult males, the neck and shoulders are greatly enlarged, and there is a mane of thicker and longer hair from the nape to the shoulders, and the chin to the chest. The head appears small. Adult females are much smaller and thinner than males through the neck, chest, and shoulders; the head and muzzle are narrower or less domed than in males.
At birth, pups are dark brown with a lighter crown and nape; a pale stripe extends from the crown to the nose, including the mystacial area. Pups begin to moult their birth coat at 2 months. Adult females and subadults of both sexes are silvery grey to brownish grey above and tan to pale yellow below. The demarcation between light and dark is high on the neck and usually extends over the insertion of the flippers. The light coloration often extends above the ears (which can appear highlighted) to the eyes, and down the sides of the muzzle. There is considerable variation in the extent of dark and light areas, particularly on the head. The crown and the top of the muzzle are often darker, giving the appearance of a stripe of dark colour running to the nose, which can be more extensive, and include most of the muzzle. On some animals there may be little discernable contrast between coloration above and below. The foreflippers are often darker above, greyish to brown. Subadult males darken as they mature, and may pass through reddish orange or brown colour phases before attaining sexual maturity. Adult males have a dark brown to charcoal coat, which can have a hint of silver-grey, particularly on the sides and back.
The dental formula is I 3/2, C 1/1, PC 6/5.
Can be confused with
Three otariids (New Zealand, Antarctic, and subantarctic fur seals) are known to occur in or near the present range of the Hooker's sea lion. Hooker's sea lions can be differentiated from fur seals, based on coloration, fur characteristics, head and muzzle shape, size of the ear pinnae, and size and shape of the outer toes on the hindflippers.
Size
It is estimated that adult males reach 3.3 m and 400 kg or more. Adult females can be at least 2 m long and weigh 160 kg. Newborns are approximately 60 to 70 cm and weigh 6.5 to 8 kg.
Geographical Distribution
The primary habitat of this species is several subantarctic islands south of New Zealand, and their surrounding waters. The principal breeding colonies are in the Auckland Islands, Campbell Island, and the Snares Islands. Historically, Hooker's sea lions had a more extensive range thatmay have included much of New Zealand.
Biology and Behaviour
The breeding season in this species is more defined than that of the similar Australian sea lion. Adult males establish small territories that have fluid boundaries. Pups are born from early December to early January.
Hooker's sea lions do not appear to be migratory although they disperse widely over their range during the non-breeding season. Some animals can be found at major rookeries and haul-outs year-round. Their activities at sea are little known.
There are no detailed accounts of feeding habits, but Hooker's sea lions take a wide variety of prey, including squid and such demersal species as flounder, octopus, and crustaceans. They are also known to take penguins, and even fur seal and elephant seal pups, on occasion. Some observations suggest they feed continuously while at sea.
Exploitation
Prehistoric use of this sea lion was made by the native Maori people of New Zealand. Commercial sealing began in the early 19th Century for hides and oil and continued until stocks were severely depleted by the middle of that century (in less than 50 years). Sporadic commercial sealing activity continued through the second world war, after which commercial sealing was banned in New Zealand. One unusual source of mortality comes from the activities of rabbits introduced by humans, which have excavated burrows near sea lion rookeries. Pups have been known to explore these burrows, become entrapped, and suffocate.
IUCN Status
Vulnerable. |
