Antarctic Fur Seal
Encyclopedia
The Antarctic fur seal (Arctocephalus gazella) is one of eight seals
in the genus Arctocephalus
, and one of nine fur seals in the subfamily
Arctocephalinae
. As its name suggests, the Antarctic fur seal is distributed in Antarctic waters
. Around 95% of the world population breeds at the Island of South Georgia
. It is named for the German naval vessel the SMS Gazelle which collected the first specimen from Kerguelen Island
. The species is also known as the Kerguelen fur seal.
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This fur seal
has a short and broad snout compared with others in the family. Adult males are dark brown in colour. Females and juveniles tend to be grey with a lighter underside. Colour patterns are highly variable, and some scientists believe that some hybridisation with subantarctic fur seal
s has occurred. Pups are dark brown, nearly black at birth. About one in 1000 Antarctic fur seals are pale 'blonde' variants.
Males are substantially bigger than females. Antarctic fur seals grow 2 m (6.5 ft) long and weigh 91 kg (200.6 lb) to 209 kg (460.8 lb). Males live for about 15 years and females up to 25.
Antarctic fur seals appear to act alone when foraging and migrating. Males breed polygynously; a strong male may have more than a dozen female partners in a single season. Territories are established on breeding grounds in October to early November, when the musty-smelling males are extremely aggressive in defence of their harem
s. Females gestate for just over a year - giving birth in November or December. Pups are weaned at about four months old. Juveniles may then spend several years at sea before returning to begin their breeding cycle.
The usual food supply is krill
, of which each Antarctic fur seal eats about a tonne in a year. Due to the enormous and growing populations of these seals, their food is a significant proportion of South Georgia's krill stocks.
The Antarctic fur seal breeds in summer on islands ranging from South Georgia at 70° W round to about 80° E (Kerguelen Islands). Additionally there is a breeding ground at Macquarie Island
, 165°E - south of New Zealand
. All these islands lie between 45° S and 60° S. The animal's winter range is not known. During these long dark months, the seal spends its time almost surely at sea close to the Antarctic ice.
A population count is due in 2007 or 2008, and estimates can only be very rough until this is carried out. Best guesses suggest there may be two to four million individuals breeding at South Georgia and 15,000 at Heard Island
. The concentrations at South Georgia are the densest aggregations of marine mammal
s on earth. Some people believe these populations have grown to such levels because the removal of whale
s by the intensive whaling
of the 20th century left a surplus of krill. Other islands in Antarctic waters may have a few hundred to a thousand such seals.
in late summer and early autumn. Adult females are gregarious but relatively asocial other than the strong bond they establish with their pups, although there are occasional aggressive encounters with nearby females or other pups and brief interactions with adult males to mate. These seals appear to be solitary when foraging and migrating. Females evidently remain at sea continually between breeding seasons, and juveniles may spend several years at sea before returning to natal sites to mate for the first time. The deepest recorded dive is about 180 m deep; the longest dive lasted 10 minutes. The diving ability of pups substantially improves during the first few months of life, and by about four months old their diving patterns are similar to those of adult females. Leopard Seal
s eat Antarctic fur seal pups. Survival of suckling pups may be particularly low in years when krill abundance near a colony is insufficient to allow lactating females to forage effectively.
, and dominant breeding males mate with as many as 20 females during a successful season. Adult males establish breeding territories on beaches in late October to mid November, preferably just along the shoreline. They are fiercely territorial during the breeding season and aggressively defend access to estrous
females from other males, mostly with stereotyped physical displays, lunges, and vocalizations. These fights can be very damaging. Many bulls die from their wounds. Males may fast during the breeding season for six to eight weeks, losing up to 1.5 kg a day. The gestation period
lasts about a year. Females give birth to a single pup between mid November and late December. They mate about 7 to 10 days later and then begin a series of foraging trips at sea that lasts for several days each. In between, they are ashore for one to several days to nurse their pups. Pups are weaned at about four months old.
The Antarctic fur seal was very heavily hunted in the 18th and 19th centuries for its pelt
by sealers from the United States
and the United Kingdom
. By the early twentieth century, the seal was regarded as commercially extinct, and perhaps completely extinct. In fact a small population continued to exist, breeding on Bird Island in South Georgia. This colony has expanded rapidly over the course of a century. The current populations on the other Antarctic islands are believed to be off-shoots of this one colony.
The species is still protected by the governments in whose waters it resides (Australia
, South Africa
, France
) and by the Convention for the Conservation of Antarctic Seals
in waters south of 60° S. The animal is also listed in Appendix 2 of CITES. However some governments with interests in the Antarctic, for instance, the United Kingdom, say that some of these protections should be lifted as the species is causing damage to vulnerable Antarctic plants.
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
in the genus Arctocephalus
Arctocephalus
The genus Arctocephalus consists of eight of the nine species of fur seal. For details see the fur seal article, or the individual species articles.-Taxonomy:* SUBORDER PINNIPEDIA* Family Otariidae...
, and one of nine fur seals in the subfamily
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Arctocephalinae
Fur seal
Fur seals are any of nine species of pinnipeds in the Otariidae family. One species, the northern fur seal inhabits the North Pacific, while seven species in the Arctocephalus genus are found primarily in the Southern hemisphere...
. As its name suggests, the Antarctic fur seal is distributed in Antarctic waters
Southern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...
. Around 95% of the world population breeds at the Island of South Georgia
South Georgia and the South Sandwich Islands
South Georgia and the South Sandwich Islands is a British overseas territory and overseas territory of the European Union in the southern Atlantic Ocean. It is a remote and inhospitable collection of islands, consisting of South Georgia and a chain of smaller islands, known as the South Sandwich...
. It is named for the German naval vessel the SMS Gazelle which collected the first specimen from Kerguelen Island
Kerguelen Islands
The Kerguelen Islands , also known as the Desolation Islands, are a group of islands in the southern Indian Ocean constituting the emerged part of the otherwise submerged Kerguelen Plateau. The islands, along with Adélie Land, the Crozet Islands and the Amsterdam and Saint Paul Islands are part of...
. The species is also known as the Kerguelen fur seal.
Description
Fur seal
Fur seals are any of nine species of pinnipeds in the Otariidae family. One species, the northern fur seal inhabits the North Pacific, while seven species in the Arctocephalus genus are found primarily in the Southern hemisphere...
has a short and broad snout compared with others in the family. Adult males are dark brown in colour. Females and juveniles tend to be grey with a lighter underside. Colour patterns are highly variable, and some scientists believe that some hybridisation with subantarctic fur seal
Subantarctic Fur Seal
The subantarctic fur seal is a fur seal found in the southern parts of the Indian and Atlantic Oceans. It was first described by Gray in 1872 from a specimen recovered in northern Australia—hence the inappropriate tropicalis specific name.- Description :The subantarctic fur seal is...
s has occurred. Pups are dark brown, nearly black at birth. About one in 1000 Antarctic fur seals are pale 'blonde' variants.
Males are substantially bigger than females. Antarctic fur seals grow 2 m (6.5 ft) long and weigh 91 kg (200.6 lb) to 209 kg (460.8 lb). Males live for about 15 years and females up to 25.
Antarctic fur seals appear to act alone when foraging and migrating. Males breed polygynously; a strong male may have more than a dozen female partners in a single season. Territories are established on breeding grounds in October to early November, when the musty-smelling males are extremely aggressive in defence of their harem
Harem
Harem refers to the sphere of women in what is usually a polygynous household and their enclosed quarters which are forbidden to men...
s. Females gestate for just over a year - giving birth in November or December. Pups are weaned at about four months old. Juveniles may then spend several years at sea before returning to begin their breeding cycle.
The usual food supply is krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, of which each Antarctic fur seal eats about a tonne in a year. Due to the enormous and growing populations of these seals, their food is a significant proportion of South Georgia's krill stocks.
Distribution and population
Macquarie Island
Macquarie Island lies in the southwest corner of the Pacific Ocean, about half-way between New Zealand and Antarctica, at 54°30S, 158°57E. Politically, it has formed part of the Australian state of Tasmania since 1900 and became a Tasmanian State Reserve in 1978. In 1997 it became a world heritage...
, 165°E - south of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. All these islands lie between 45° S and 60° S. The animal's winter range is not known. During these long dark months, the seal spends its time almost surely at sea close to the Antarctic ice.
A population count is due in 2007 or 2008, and estimates can only be very rough until this is carried out. Best guesses suggest there may be two to four million individuals breeding at South Georgia and 15,000 at Heard Island
Heard Island and McDonald Islands
The Heard Island and McDonald Islands are an Australian external territory and volcanic group of barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size is in area and it has of coastline...
. The concentrations at South Georgia are the densest aggregations of marine mammal
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...
s on earth. Some people believe these populations have grown to such levels because the removal of whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s by the intensive whaling
Whaling
Whaling is the hunting of whales mainly for meat and oil. Its earliest forms date to at least 3000 BC. Various coastal communities have long histories of sustenance whaling and harvesting beached whales...
of the 20th century left a surplus of krill. Other islands in Antarctic waters may have a few hundred to a thousand such seals.
Behavior
Adult and subadult males may form groups while moulting along the Antarctic PeninsulaAntarctic Peninsula
The Antarctic Peninsula is the northernmost part of the mainland of Antarctica. It extends from a line between Cape Adams and a point on the mainland south of Eklund Islands....
in late summer and early autumn. Adult females are gregarious but relatively asocial other than the strong bond they establish with their pups, although there are occasional aggressive encounters with nearby females or other pups and brief interactions with adult males to mate. These seals appear to be solitary when foraging and migrating. Females evidently remain at sea continually between breeding seasons, and juveniles may spend several years at sea before returning to natal sites to mate for the first time. The deepest recorded dive is about 180 m deep; the longest dive lasted 10 minutes. The diving ability of pups substantially improves during the first few months of life, and by about four months old their diving patterns are similar to those of adult females. Leopard Seal
Leopard Seal
The leopard seal , also referred to as the sea leopard, is the second largest species of seal in the Antarctic...
s eat Antarctic fur seal pups. Survival of suckling pups may be particularly low in years when krill abundance near a colony is insufficient to allow lactating females to forage effectively.
Reproduction
The breeding system of the Antarctic fur seal is polygynousPolygyny
Polygyny is a form of marriage in which a man has two or more wives at the same time. In countries where the practice is illegal, the man is referred to as a bigamist or a polygamist...
, and dominant breeding males mate with as many as 20 females during a successful season. Adult males establish breeding territories on beaches in late October to mid November, preferably just along the shoreline. They are fiercely territorial during the breeding season and aggressively defend access to estrous
Estrous cycle
The estrous cycle comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. Estrous cycles start after puberty in sexually mature females and are interrupted by anestrous phases or pregnancies...
females from other males, mostly with stereotyped physical displays, lunges, and vocalizations. These fights can be very damaging. Many bulls die from their wounds. Males may fast during the breeding season for six to eight weeks, losing up to 1.5 kg a day. The gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
lasts about a year. Females give birth to a single pup between mid November and late December. They mate about 7 to 10 days later and then begin a series of foraging trips at sea that lasts for several days each. In between, they are ashore for one to several days to nurse their pups. Pups are weaned at about four months old.
Interactions with humans
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...
by sealers from the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. By the early twentieth century, the seal was regarded as commercially extinct, and perhaps completely extinct. In fact a small population continued to exist, breeding on Bird Island in South Georgia. This colony has expanded rapidly over the course of a century. The current populations on the other Antarctic islands are believed to be off-shoots of this one colony.
The species is still protected by the governments in whose waters it resides (Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
) and by the Convention for the Conservation of Antarctic Seals
Convention for the Conservation of Antarctic Seals
The Convention for the Conservation of Antarctic Seals is part of the Antarctic Treaty System. It was signed at the conclusion of a multilateral conference in London on February 11, 1972...
in waters south of 60° S. The animal is also listed in Appendix 2 of CITES. However some governments with interests in the Antarctic, for instance, the United Kingdom, say that some of these protections should be lifted as the species is causing damage to vulnerable Antarctic plants.
Further reading
- Wynen, Louise P. et al. "Postsealing genetic variation and population structure of two species of fur seal (Arctocephalus gazella and A. tropicalis)". Molecular EcologyMolecular ecologyMolecular ecology is a field of evolutionary biology that is concerned with applying molecular population genetics, molecular phylogenetics, and more recently genomics to traditional ecological questions...
. Vol. 9. (2000). pp. 299–314.