The subantarctic fur seal, Arctocephalus tropicalis Gray, 1872, is widely distributed throughout the entire southern hemisphere and breeds on temperate islands in the south Atlantic and Indian oceans with a collective population size of approximately 300 000 individuals.
Description/How to recognise a subantarctic fur seal?
Subantarctic fur seal, is closely related to the Antarctic fur seal, Arctocephalus gazella. The two species co-inhabit Prince Edward Islands, Îles Crozet and Macquarie Island where they have established populations. Due to their relatedness, they sometimes hybridise, mostly at Marion Island. They have a short and flat snout.
Under favourable conditions they may live up to to 25 years. The females grow up to 50 km in weight and 1.5 m in body length, while males may grow up to 2 m in length and 150 kg in body weight. They have a dark colour on their backs with brownish bellies. However, the pups are black at birth and attain the adult colouration as they grow and moult.
Getting around
They move and swim using their flippers
Communicating
The subantarctic fur seal uses auditory, visual and tactile communication. One interesting feature of this species’ communication is that, when the females call for their pups, multiple pups respond, but the mother fur seal is able to distinguish her pup’s call among hundreds of other pups.
Distribution
To date, scientific research recorded the largest populations in Amsterdam and Gough islands, as well as the Prince Edward Islands. Prince Edward Islands comprises of Marion Island and Prince Edward Island. At Marion Island where South Africa has the Marion Research Station, they produce about 50 000 pups per year and at Prince Edward Island they produce approximately 30 000 pups per year.
Habitat
The subantarctic fur seal is adapted to life in the sea. However, they breed on shore, usually islands.
Food
Subantarctic fur seals are carnivores, and they feed on fish, squids, shrimps, crabs, lobsters, and occasionally penguins. They prefer hunting for their prey in shallow waters.
SEX and LIFE CYCLES
Sex: Subantarctic fur seals are polygynous. The male controls and defends a harem consisting of approximately 15 (up to 20) females. The mating occurs between October and January. The females give birth after 51 weeks. Generally, males have a shorter life span, reaching about 15 years of age, while females can live up to 20 years.
Family life: They live is large colonies with thousands of members within which a male secures his own territory and controls a harem with at most 20 females. Females spends most of their time looking after their pups while males either are at the colony or out hunting at sea.
THE BIG PICTURE
Friends and Foes
The known predators/enemies of subantarctic fur seals are killer whale (Orcinus orca) and various species of sharks.
Smart Strategies
The subantarctic fur seal can swim up to 1 500 km in search of food. They are well adapted to their natatorial life style. In higher ambient temperatures they are active during the day, and during lower temperatures they are active at night.
Poorer world without me
They serve as food source for sharks and killer whales and as predator they control the populations of fishes, cephalopods and other crustaceans which they prey upon. Back in the 18th century they were hunted for their pelts. This practice is strictly against the law now.
People & I
Conservation status and what the future holds
Arctocephalus tropicalis is currently listed in the IUCN Red List as Least Concern. This comes after the species recovered from the mass hunting of the 18th century. In CITES, it is listed in Appendix II. The existing threats could include the effects of climate change and the ongoing hybridisation with A. gazella in some colonies.
RELATIVES
There are seven known species and four subspecies in the genus Arctocephalus, namely: A. australis (Zimmermann, 1783), A. forsteri (Lesson, 1828), A. galapagoensis Heller, 1904, A. gazella (Peters, 1875), A. philippii (Peters, 1866), A. pusillus (Schreber, 1775), and the subspecies: A. philippii philippii (Peters, 1866), A. philippii townsendi Merriam, 1897, A. pusillus doriferus Wood Jones, 1925 and A. pusillus pusillus (Schreber, 1775). Arctocephalus tropicalis, subantarctic fur seal, is closely related to A. gazella, antarctic fur seal.
Official Common Name: Subantarctic fur seal
Scientific Name and Classification:
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Otariidae
Genus: Arctocephalus
Species: A. tropicalis Gray, 1872
Derivation of scientific name (if known)
Common names: Subantarctic fur seal, Amsterdam Island fur seal (Eng.); subantarktiese pelsrob (Afr.).
References and further reading
- Beauplet, G., Dubroca, L., Guinet, C., Cherel, Y., Dabin, W., Gagne, C. & Hindell, M. 2004. Foraging ecology of subantarctic fur seals, Arctocephalus tropicalis, breeding on Amsterdam Island: seasonal changes in relation to maternal characteristics and pup growth. Mar Ecol Prog Ser 273: 211–225.
- Bester, M.N. 1990. Reproduction in the male sub‐Antarctic fur seal, Arctocephalus tropicalis. J Zool 222: 177–185.
- Dabin, W., Beauplet, G., Crespo, E.A. & Guinet, C. 2004. Age structure, growth, and demographic parameters in breeding-age female subantarctic fur seals, Arctocephalus tropicalis. Can J Zool 82: 1043–1050.
- Guinet, C., Servera, N., Deville, T. & Beauplet, G. 2005. Changes in subantarctic fur seal pups’ activity budget and diving behaviours throughout the rearing period. Can J Zool 83 :962–970.
- Reisinger, R.R., de Bruyn, P.J.N. & Bester, M.N. 2011. Predatory impact of killer whales on pinniped and penguin populations at the Subantarctic Prince Edward Islands: fact and fiction. J Zool 285: 1–10.
- Souto, L.R.A., Abrão-Oliveira, J.G., Maia-Nogueira, R. & Dórea-Reis, L.W. 2009. Interactions between subantarctic fur seal (Arctocephalus tropicalis) and cookiecutter shark (Isistius plutodus) on the coast of Bahia, north-eastern Brazil. Mar Biodivers Rec 2:e123.