© Ilustration by Pieter Folkens in Encyclopedia of Marine Mammals 3ra Edition
South American Fur Seal
Scientific name: Arthocephalus australis
As other Pinnipeds (carnivorous mammals with feet modified into flippers), this species is amphibious alternating periods of feeding at sea with periods of permanence on land where it reproduces (mating and birth). It has a strong sexual dimorphism, with adult males being larger and heavier than adult females. Males may reach up to 2 m (6.5 ft) and 120-160 kg (265 - 350 lb), whilst females do not exceed 1.5 m (5 ft) and 40-60 kg (88 - 130 lb). Newly born are between 50 to 65 cm (1.64 – 2.13 ft) of length, and 3 to 7.5 kg (6.6 – 16.5 lb).
It is found along the coasts of both Southwestern Atlantic Ocean (Southern Brazil, Uruguay, Argentina and Falkland (Malvinas) Islands) and Southeastern Pacific Ocean (Southern Chile). It is a gregarious species (they live in groups), and form large colonies in islands, preferring grounds with steep rocks and difficult access. The colonies with the greatest number of births are located in Falkland (Malvinas) Islands, and Isla Lobos (Uruguay). There are more reproductive colonies in Southern Chile, Isla de los Estados (Argentina), and north and center of Patagonia. On the other hand, there are non-reproductive colonies, where individuals get together to rest, such as the ones in Southern Brazil, Buenos Aires province coast, and islands and islets in Patagonia.
It is a polygynous species. Males defend a territory with harems containing 2 to 13 females, for an average of 5-6 females per male. Breeding season is from the second week of November until the first week of February, with a peak in births in mid-December, and a peak in mating a few days later than that. After a twelve-month gestation period, females give birth to an only pup each breeding season. Females nurse their calves for 8 to 12 months. Females reach sexual maturity at 2 - 4 years old. Males are sexually mature at 5-6 years old, but is not until 7-8 years old that they have the capacity to retain a female and copulate. Life span is about 20 years, although females live longer than males.
The species occupies a high trophic level in marine ecosystems. They feed both in coastal areas and open ocean, reaching the continental shelf brake. Within the water column, there have been records of individuals diving between 50 m and 600 m deep. Its diet is mainly composed of fish, squid and crustaceans, but feeding varies according to resources availability. Among its predators we can find broadnose sevengill shark (Notorhynchus cepedianus) and orca (Orcinus orca).
This species has been exploited by hunter-gatherers since thousands of years ago. Later, it suffered commercial exploitation throughout the XVIII to the XX century. As a result, its abundance and original distribution where reduced to small colonies spread within the previously occupied area.
Map showing the worldwide distribution of South American four seal.
The stop in commercial hunting and creation of conservation legislation have allowed a slow recovery of the various populations. Currently, the species is protected throughout its distribution area, and in 2016, the International Union for Conservation of Nature (IUCN) classified it as Least Concern (LC). Amongst its main treats to conservation we can mention reduction on prey availability due to fisheries and habitat degradation.
- Bastida, R., Rodríguez, D., Secchi, E., & Silva, V. (2007). Mamíferos acuáticos de Sudamérica y Antártida. Primera edición. Vázquez Mazzini Editores: Buenos Aires.
- Cárdenas-Alayza, S. (2018). South American fur seal Arctocephalus australis. En: Würsig, B., Thewissen, J. G. M., & Kovacs, K. M. (eds.) Encyclopedia of Marine Mammals. Third edition. Academic Press: Londres.
- Cárdenas-Alayza, S., Oliveira, L., & Crespo, E. (2016). Arctocephalus australis. The IUCN Red List of Threatened Species 2016: e.T2055A45223529. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T2055A45223529.en
- Vales, D. G., Mandiola, A., Romero, M. A., Svendsen, G., Túnez, J. I., Negrete, J., & Grandi, M. F. (2019). Arctocephalus australis. En: SAyDS–SAREM (eds.) Categorización 2019 de los mamíferos de Argentina según su riesgo de extinción. Lista Roja de los mamíferos de Argentina. http://cma.sarem.org.ar/index.php/es/especie-nativa/arctocephalus-australis