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Northern Fur Seal – Pinniped

EARED SEALS

Northern Fur Seal (Callorhinus ursinus)

The Northern Fur Seal (Callorhinus ursinus) is found in the North Pacific Ocean from Japan across to Mexico and northwards, stretching to the Sea of Okhotsk and the Bering Sea. They are the only species of fur seal not in the Arctocephalus genus, but again, the latin name references the bear-like appearance of the seals with ‘ursinus’, and strangely ‘callorhinus’ translates as beauty nose! Due to the fact certain populations are decreasing severely, C. ursinus are categorised as Vulnerable by the IUCN. Estimated population size = 1,290,000.
C. ursinus are large, sexually dimorphic fur seals (males up to 2.1 m long/ 275 kg, females up to 1.5 m/ 60 kg). They have heavy bodies with long hind flippers and very broad fore flippers, which are fleshy rather than fur covered. The males also have very broad shoulders and a thick mane around their hefty necks. The heads of this species are fairly small, with a little snub, downward-curving muzzle, and a flat head. Males are generally dark brown to black, with hints of reddish, silver-grey or golden in their fur, particularly on the mane, underarms, crown of head, and face. Females are dark brown, to dusky blonde, to grey, usually highlighted on their undersides, particularly the chest, and face.
Feeding behaviour:
This species eats a wide variety of cephalopods and fish, depending on location of the population and season. They tend to favour pelagic species both in the photic zone, as well as those that migrate there to feed, and are opportunistic. Some examples of prey include: squid, anchovy, hake, saury, salmon, rockfish, pollock, herring, cod, capelin, mackerel, lanternfish, sand lance and smoothtongue. Foraging effort is mostly crepuscular, and carried out far offshore. These animals are one of the most pelagic of all pinnipeds, spending the majority of their lives at sea.
Breeding behaviour:
Sexual maturity – males 4-5 years old/ females 2-5 years old.
Male C. ursinus start arriving at the breeding rookeries in the early summer (May), and establish territories which they defend vehemently from their conspecifics. The species is polygynous and males may mate with upwards of 50 females, whom he also aggressively defends from his neighbours. Occasionally females have been killed in these battles. There is a 3.5-4 month delayed implantation period after mating, which brings the entire gestation to approximately one year, meaning females arrive to give birth in June-August after they have mated in the previous season. The pups have blackish-chocolatey brown coats, often with buff spots under the flippers, and on the sides of the body and face. This coat is moulted at 3-4 months of age. Suckling continues for around 1 week before the mother’s foraging trips begin. This then begins a cycle of foraging for just over a week, and returning to nurse for just a couple of days. Over the lactation period, which lasts just 4 months, pups are only visited 8-12 times. When the females leave in October, the weaned pups will stay until November on the shore before heading out to sea themselves. The adults also moult after birth of the pups, which lasts about 4 or 5 months, meaning that the rookeries empty out altogether in November. Longevity in C. ursinus is approximately 25-26 years.
There are no subspecies of C. ursinus.

Photos: Amanda Warlick

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