The subantarctic fur seal (''Arctocephalus tropicalis'') is a species of arctocephaline found in the southern parts of the Indian,

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

, and

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

Oceans. It was first described by

Gray Grey (more frequent in British English) or gray (more frequent in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning that it has no chroma. It is the color of a cloud-covered s ...

in 1872 from a specimen recovered in northern Australia—hence the inappropriate specific name ''tropicalis''.

Description

The

subantarctic The sub-Antarctic zone is a physiographic region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46th parallel south, 46° and 60th parallel south, 60° south of t ...

fur seal is medium in size compared with other fur seals. The two sexes are strongly

sexually dimorphic Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

: males grow to 2m and 160 kg, whereas females are substantially smaller—1.4m and 50 kg. Subantarctic fur seals have creamy-orange chests and faces. Their bellies are more brownish. Males have a dark grey to black back, while females are a lighter grey. Males have a characteristic dark tuft of hair on the top of their head that stands erect when they are excited. Pups are black at birth, but molt at about 3 months old. The snout is short and flat, and the flippers are short and broad. Subantarctic fur seals live for about 20–25 years.

Distribution

Arctocephalus tropicalis CrozetIslands pup

''Arctocephalus tropicalis'', the subantarctic fur seal, is geographically widespread; as their specific and common names imply, they generally breed in and inhabit more northerly (subantarctic, or "tropical") locations than the Antarctic fur seal (''Arctocephalus gazella'') does. The largest known breeding colonies are on

Gough Island Gough Island ( ), also known historically as Gonçalo Álvares, is a rugged volcanic island in the South Atlantic Ocean. It is a dependency of Tristan da Cunha and part of the British overseas territory of Saint Helena, Ascension and Tristan d ...

, in the South Atlantic, and

Île Amsterdam (), also known as Amsterdam Island or New Amsterdam (), is an island of the French Southern and Antarctic Lands in the southern Indian Ocean that together with neighbouring Île Saint-Paul to the south forms one of the five districts of the t ...

, in the southern reaches of the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

. Breeding grounds are also located on Marion Island in the

Prince Edward Islands The Prince Edward Islands are two small uninhabited subantarctic volcanic islands in the southern Indian Ocean that are administered by South Africa. They are named Marion Island (named after Marc-Joseph Marion du Fresne, 1724–1772) and P ...

—which is shared with the Antarctic fur seal—as well as the

Crozet Islands The Crozet Islands (; or, officially, ''Archipel Crozet'') are a sub-Antarctic archipelago of small islands in the southern Indian Ocean. They form one of the five administrative districts of the French Southern and Antarctic Lands. History ...

and

Macquarie Island Macquarie Island is a subantarctic island in the south-western Pacific Ocean, about halfway between New Zealand and Antarctica. It has been governed as a part of Tasmania, Australia, since 1880. It became a Protected areas of Tasmania, Tasmania ...

. In places where the two species intermingle, ''A. tropicalis'' can be identified visually by the lighter, orange colouring on its chest. Occasional hybridisation has been known to occur between the two seals in these areas. About 300,000 subantarctic fur seals are remaining today, a number likely to be substantially lower than when they were first discovered in 1810, as they were hunted excessively for their pelts throughout the 19th century. Populations from ancient history, prior to human contact, were likely even higher. However, the species recovers rapidly, it seems, albeit in areas wherein it is protected by the Convention for the Conservation of Antarctic Seals (CCAS). A small population on Heard Island is considered

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

. The Antarctic fur seal was also rigorously hunted, to the point of all but one breeding colony remaining by the year 1900, resulting in an increasingly low species-wide genetic variability; meanwhile, the genetic diversity amongst subantarctic fur seals has remained high. There appear to be three distinct genetic lineages in the subantarctic species, though none of them represent any particular geographical area.

Behavior

Breeding

Arctocephalus tropicalis an injured male resting in the grass

As with other otariids, subantarctic fur seals gather in large rookeries on the shore to breed. They have a

polygynous Polygyny () is a form of polygamy entailing the marriage of a man to several women. The term polygyny is from Neoclassical Greek πολυγυνία (); . Incidence Polygyny is more widespread in Africa than in any other continent. Some scholar ...

mating system in which dominant males will defend their harem of 6–20 females. Fights between males for mating rights are violent and can result in severe injuries. Males will also compete against each other through vocalizations and threat displays. The breeding season takes place from November to January. Gestation lasts around 51 weeks, at the end of which the female will give birth to a single pup. 8–12 days after giving birth, they will breed again. Males are capable of mating at around 3–4 years of age, but they are unlikely to be able to hold a harem until they are 10–11 years old. Females reach sexual maturity at around 5 years.

Life cycle

2021-02 Amsterdam Island - Subantarctic fur seal 55

After being born, pups spend around 11 months feeding on their mother's milk, which contains around 39% fat. The length of their lactation period is typical of otariid seals, and contrasts with the far shorter 4 month lactation period of the Antarctic fur seal. They stay at the rookery during this period. Weaning occurs shortly before the next offspring is born. They molt their black coat at around 3 months of age. As adults, they continue to molt their coat annually between March and May.

Diet and foraging

Subantarctic fur seals hunt in shallow waters at night, when myctophid fish come close to the surface. They also feed on

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

. Other prey can include

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, and occasionally rockhopper penguins and other

seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...

s. A study conducted on subantarctic fur seals at Marion Island from 1996 to 2000 concluded that Myctophid fish constituted the largest part of the seals' diet, with fish from the families

Channichthyidae The crocodile icefish or white-blooded fish comprise a family (biology), family (Channichthyidae) of notothenioid fishes, fish found in the Southern Ocean around Antarctica. They are the only known vertebrates to lack hemoglobin in their blood as ...

Paralepididae Barracudinas are any member of the marine mesopelagic fish family (biology), family Paralepididae: 50 or so extant species are found almost worldwide in deep waters. Several genera, including ''Holosteus'' and ''Drimys (fish), Drimys'', are kn ...

, Nototheniidae,

Microstomatidae The Microstomatidae (pencil smelts) are a family of marine smelts native to the Atlantic, Indian, and Pacific Oceans. Their bodies are small and slender, with large eyes and a small mouth. The dorsal fin is located behind the midpoint of their b ...

and Notosudidae being eaten in smaller numbers. The size of prey fish ranged from small Myctophids with an average length of 25mm, to large Patagonian toothfish with an average length of 70 cm.

Travelling

Subantarctic fur seals are unique in their tendency to occasionally travel very long distances from their home islands. Young males have been seen travelling thousands of miles from their native habitat, being sighted in countries such as

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...

, Australia and

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. In July 2015, a young male seal was caught and later released by local fishermen off the coast of

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

, more than 4,000 miles (6.400 km) from its home. This is the furthest north that a subantarctic fur seal has been recorded travelling to. Lactating females have been recorded travelling up to 530 km from their colonies in order to forage for food.

Gallery

File:2021-03 Amsterdam Island - Subantarctic fur seal 97.jpg File:2021-02 Amsterdam Island - Subantarctic fur seal 53.jpg File:2021-08 Amsterdam Island - Subantarctic fur seal 57.jpg File:2021-02 Amsterdam Island - Subantarctic fur seal 64.jpg File:2021-04 Amsterdam Island - Subantarctic fur seal 14.jpg File:2021-04 Amsterdam Island - Subantarctic fur seal 15.jpg File:2021-08 Amsterdam Island - Subantarctic fur seal 65.jpg File:2021-03 Amsterdam Island - Subantarctic fur seal 98.jpg File:2021-06 Amsterdam Island - Subantarctic fur seal 26.jpg File:2021-02 Amsterdam Island - Subantarctic fur seal 62.jpg File:2021-06 Amsterdam Island - Subantarctic fur seal 39.jpg File:2021-07 Amsterdam Island - Northern giant petrel 19.jpg File:2021-09 Amsterdam Island - Northern rockhopper penguin 04.jpg File:Arctocephalus tropicalis a male lightly scared.JPG File:Strasbourg Musée zoologique (27).JPG File:Gazelle-arctocephalus.jpg