Australian Fur Seal

Introduction

The Australian Fur Seal is the largest fur seal found in Australian waters.

Identification

Fur seals have large eyes, a pointed face with whiskers and sharp teeth. The Australian Fur Seal, Arctocephalus pusillus doriferus is the largest of all the fur seals. It has a broad head, pointed snout and long backward sweeping facial vibrissae (whiskers). The body is robust and covered in thick brown layered hair except on the front and back flippers. The Australian Fur Seal is sexually dimorphic (males and females are visibly different). The males are larger than the females and when mature carry a dark mane of coarse hair. They have a set of carnivore-like teeth similar to those of a large dog or bear. Like all members of the Family Otariidae (Fur seals and sea lions) they can raise their body onto their front flippers to move around on land.

Habitat

Australian Fur Seals frequent coastal waters and oceans. Their preferred habitat especially for breeding is rocky islands, which include boulder or pebble beaches and gradually sloping rocky ledges.

Distribution

The Australian Fur Seal has a relatively restricted distribution around the islands of Bass Strait, parts of Tasmania and southern Victoria. They can be seen hauling out (coming ashore) on islands off South Australia and areas of southern New South Wales such as Montague Island with the occasional animal appearing as far north as the mid north coast of New South Wales.

As it is closely related to the South African Fur Seal, its populations worldwide are reasonable secure although it is occasionally commercially hunted in South Africa. In Australia it is fully protected although its numbers are probably still only half those of the historic pre sealing days. It continues to be vulnerable to disturbance at its breeding sites and suffers some loses as a result of conflict with commercial fishing operations.

Feeding and diet

Australian Fur Seals feed on a variety of bony fish species plus squid and octopus. They are voracious and skilful hunters in the water and are not adverse to taking advantage of situations where fish are corralled by nets and fish farms.

Other behaviours and adaptations

With its streamlined shape and strong flippers, the Australian Fur Seal is an agile swimmer and can dive to depths of 200 m to catch fishes and squids. Despite its cumbersome appearance, it is also quite mobile on land, even over rocky terrain.

Fur seals differ from other seals (true seals) because they have external ears and the ability to use all four limbs to move across land. Also, fur seals have two layers of fur while other seals have only one layer.

Breeding behaviours

Australian Fur Seals come ashore each year and form breeding colonies. The adult males come ashore first and establish territories. Females congregate within these areas and are defended by the resident male often with considerable aggression towards the females and other males. Females spend most of the gestation period at sea, coming ashore just before the birth of a single pup (sometimes two) between October and December. Females generally mate again 6 - 10 days later.

The Australian Fur Seal has what is referred to as 'delayed implantation', which means the fertilised egg remains dormant for some time before implanting and resuming development. This ensures that the pups will always be born in summer when chances of survival are highest because of the warmer weather and abundant food supply.

The pup population suffers a high mortality rate in those first two months of life especially when the mothers are away at sea feeding. Pups are weaned at four to six months old but may still remain with the mother for a further six months or more.

Conservation status

During the 1800s the Australian Fur Seal was heavily hunted for its coat and the population dropped from several hundred thousand to only 20,000. Entanglement in discarded fishing gear is also a threat. All Australian marine mammals are protected and the Australian Fur Seal population is making a recovery.

Predators

In the wild, seals are eaten by several species of sharks including the White Shark.

References

• Bryden, M., Marsh, H. and Shaughnessy, P. 1998. Dugongs, Whales, Dolphins and Seals. A guide to the sea mammals of Australasia. Allen & Unwin, St Leonards, Australia.
• King, J.E.1983. Seals of the World. University of Queensland Press. St Lucia, Australia.
• Reeves, R. R., Stewart, B. S., Clapham, P. J. and Powell, J. A. 2002. National Audubon Society Guide to Marine Mammals of the World. Chanticleer Press, Inc New York, USA.