Brown fur seal
The brown fur seal (Arctocephalus pusillus), also known as the Cape fur seal, South African fur seal and the Australian fur seal is a species of fur seal.
The brown fur seal is the largest and most robust fur seal. It has a large and broad head with a pointed snout that may be flat or upturned slightly. The pinnae and vibrissae are long, and the vibrissae may extend backward past pinnae, especially in adult males. The foreflippers are covered with sparse hair over about three quarters of their length. The hindflippers are short relative to the large body, with short fleshy tips on the digits. The size and weight of the brown fur seal depends on the subspecies. Males of the African subspecies (A. p. pusillus) are 2.3 metres (7.5 ft) in length on average and weigh from 200–350 kilograms (440–770 lb). Females are smaller, averaging 1.8 metres (5.9 ft) in length and weighing an average of 120 kilograms (260 lb). Males of the Australian subspecies (A. p. doriferus) are 2–2.2 metres (6.6–7.2 ft) in length and weigh 218–360 kilograms (480–790 lb). Females are 1.2–1.8 metres (3.9–5.9 ft) length and weigh 36–110 kilograms (79–240 lb).
Adult male brown fur seals are dark gray to brown with a darker mane of short coarse hairs and a light belly, while adult females are light brown to gray with a light throat and darker back and belly. The foreflippers of the fur seal are dark brown to black. Pups are born black and molt to gray pelage with a pale throat within three to five months. The skull of the African subspecies has a larger crest between the mastoid process and the jugular process of the exoccipital.
The African fur seal lives around the southern and south southwestern coast of Africa from Cape Cross in Nambia and around the Cape of Good Hope to Black Rocks of Cape province. The Australian fur seal lives in Bass Strait, at four islands off Victoria in southeastern Australia and five islands off Tasmania. Brown fur seals prefer to haul out and breed on rocky islands, rock ledges and reefs and pebble and boulder beaches. However some large colonies can be found on sandy beaches. Fur seals spend of the year at sea but are not too far from land. They have been recorded 160 km from land but this is not common.
It appears that the African fur seal’s diet is made of up to 70% fish, 20% squid and 2% crab. Also eaten are other crustaceans, cephalopods and sometimes birds. The Australian fur seal mostly eats squid, octopus, fish and lobsters. The brown fur seal dives for its food. The African subspecies can dive as deep as 204m and for as long as 7.5 minutes. The Australian subspecies generally feeds at lower depths, diving on average 120m and can reach as deep as 200m.
The brown fur seal's main predator is the great white shark, although they are also preyed upon by various other animals as well, such as orcas. Land-based predators include black-backed jackals and brown hyenas on the Skeleton Coast in Namibia. In False Bay, the seals employ a number of antipredatory strategies while in shark-infested waters such as:
- Swimming in large groups
- Low porpoising to increase subsurface vigilance
- Darting in different directions to cause confusion when attacked
- Riding near the dorsal fin to keep out of reach of the shark's jaws when attacked.
Brown fur seals often gather into colonies on rookeries in numbers ranging from 500-1500, at least for the Australian subspecies. While fur seal spend most of the year at sea, they never fully evacuate the rookeries as mothers and pups return to them throughout the year. There is no established dispersal from a colony although some fur seals from one colony have been found at another. True boundaries do not exist between the colonies. When at sea fur seals travel in small feeding groups. Brown fur seals begin to breed in the middle of October which is when males haul out on shore to establish territories though display, sparring and sometimes actual combat. They will fast at this time and not eat until after mating in November or December. When the female arrives, they fight among themselves for territories to give birth in. Female territories are smaller than those of males and are always located within them. Females within a male’s territory can be considered part of his harem. However, males do not herd the females who are free to choose their mate and judging them based on the value of his territory. For the Australian fur seal 82% of copulations are done by males whose territories are located directly on the water. Copulation between the male and his females begins six day after they give birth to their pups conceived from the previous year. However there is a delay in the implantation of the blastocyst, which last four months in the African subspecies and three months in the Australian subspecies. Gestation for the brown fur seal lasts an average of 11.75 months.
After mating, females begin alternating brief periods of foraging at sea with several days ashore nursing their pups. Foraging trips last about seven days in winter and about four days in summer and autumn. When a mother returns from sea to feed her pup, she emits a loud call which attracts all the nearby pups but she only responds to her pup. It is possible she can recognize her pup by smell. When left alone, pups gather in groups and play during the evening. Pups are usually weaned at 4–6 months old.
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This species is an inquisitive and friendly animal when in the water, and will often accompany SCUBA divers. They will swim around divers for periods of several minutes at a time, even at a depth of 60m. On land, they are far less relaxed and tend to panic when people come near them.
Australian fur seals were hunted intensively between 1798 and 1825 for commercial reasons. Seal hunting stopped in Australia in 1923, and their population is still recovering. Breeding and haul-out sites are protected by law. South African fur seals have a very robust and healthy population. Harvesting of seals was outlawed in South Africa in 1990.
Brown fur seals are still harvested in Namibia. Around 85,000 pups a year are clubbed to death; their fur is bought by Turkish businessman Hatem Yavuz, and sold to the fashion industry. Many animal activist groups strongly condemn this culling. The seal is a protected species in South Africa; there are now only a million seals in the wild. The quota set by the Namibian government for culling the pups, until 2019, will be a million pups.
- ^ Hofmeyr, G. & Gales, N. (2008). Arctocephalus pusillus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 30 January 2009.
- ^ a b c d e f g h i Randall R. Reeves, Brent S. Stewart, Phillip J. Clapham and James A. Powell (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf, Inc. ISBN 0375411410.
- ^ a b c d e f g h i j King, J. 1983. Seals of the World. Ithaca, New York: Comstock Publishing Associates.
- ^ a b c d Schliemann, H. 1990. Eared Seals and Walruses. Pp. 168-203 in B. Grzimek, ed. Grzimek's Encyclopedia of Mammals. New York: McGraw-Hill.
- ^ a b c d e f Riedman, M. 1990. The Pinnipeds: Seals, Sea Lions, and Walruses. Berkeley: University of California Press.
- ^ Anti-Predatory Strategies of Cape Fur Seals at Seal Island