Arctocephalus australis, Zimmermann, 1783
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publication ID |
https://doi.org/ 10.5281/zenodo.6604474 |
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DOI |
https://doi.org/10.5281/zenodo.6604504 |
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persistent identifier |
https://treatment.plazi.org/id/965C87FE-1E59-564A-9CC8-948086C5F22C |
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treatment provided by |
Diego |
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scientific name |
Arctocephalus australis |
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South American Fur Seal
Arctocephalus australis View in CoL
French: Otarie des Falkland / German: Stidamerika-Seebar / Spanish: Lobo marino de dos pelos
Other common names: Falkland Fur Seal, Peruvian Fur Seal, Southern Fur Seal
Taxonomy. Phoca australis Zimmermann 1783 ,
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“Wohnt um Juan Fernandez, und uberhaupt in dortigen Meeren” (= lives to Juan Fernandez, and even in local areas .
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Taxonomy of A. australis is uncertain at the subspecific level. Recent work has established that fur seals from Brazil to Argentina, including the Falkland Islands (Malvinas), those in the south-western Pacific Ocean in southern Chile, and another group form central Peru to northern Chile are separate Evolutionarily Significant Units (ESUs). The strongest differences reported were between previously unrecognized ESUs from Peru to northern Chile and in the western South Atlantic Ocean. Also noteworthy was the almost 20° latitude gap with no A. australis between the two ESUs in the eastern South Pacific Ocean providing a strong barrier isolating the Peruvian and northern Chilean ESUs from the other ESUs. All three ESUs are probably worthy of subspecific distinction. Although several schemes have been suggested, taxonomy and naming of these ESUs remains unresolved. The relationship of A. forsteri to the A. australis ESUsis also controversial with one recommendation that A. forsteri is yet another subspecies of the A. australis complex. More research also needs to be done on the relationship of A. galapagoensis to the A. australis ESUs. Monotypic.
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Distribution. S South America, from Uruguay S to Cape Horn and the Falkland Is on the Atlantic side; on the Pacific side, the Magellanic region and from C Peru to N Chile; regularly visits S Brazil. View Figure
Descriptive notes. Total length up to 190 cm (males) and 150 cm (females); weight 120-160 kg and maybe to as much as 200 kg (males) and 40-50 kg (females). Newborns are 40-65 cm and 3.3-5.5 kg. Dental formula I 3/2, C 1/1, PC 6/5 (x 2) 36. South American Fur Seals are sexually dimorphic. Adults are stocky, with long prominent ear pinnae, and pale vibrissae of moderate length. Males have thick neck and large shoulders, with mane of longer guard hairs from crown to shoulders, including neck and upper chest. Muzzle is straight, of medium length, and tapers to nose, or rhinarium, which is a bit enlarged, giving an individual a slightly upturned muzzle silhouette. Crown is rounded, and forehead of males is noticeably steep. Flippers have dark, sparse, short fur that extends beyond wrists and ankles onto dorsal surface of flippers that are otherwise covered in black leathery skin. As they mature, male South American Fur Seals become uniformly dark brown but show silvery frosting. Adult females and subadults are brown to gray-black on back and show a mix of paler tans, grays, and ruddy browns on their bellies. Chest and neck are generally lighter in color, in contrast to dark face and head, although area of muzzle containing vibrissae is paler. Ear pinnae are pale, and fur at base may be light colored in adult females and subadults. Young are born with long black fur, but face and muzzle may have pale areas.
Habitat. Continental shelf and continental slope waters, occasionally as far as 600 km from shore. Terrestrial habitats of South American Fur Seals are on rocky coasts and ledges and shorelines with boulders. These locations usually provide some sheltering from the strong sun. Predators include Killer Whales (Orcinus orca), sharks, South American Sea Lions ( Otaria byronia ), and Leopard Seals (Hydrurga leptonyx). Vampire bats (Desmodontinae) take blood meals from flippers of dozing South American Fur Seals.
Food and Feeding. Diets of South American Fur Seals change depending on season and foraging area. Lactating females are known to feed nocturnally. Prey includes vertically migrating species and mid-water and bottom-dwelling species. Around islands off Uruguay, fish is the dietary mainstay of the South American Fur Seal. Their prey includes such pelagic and demersal species such as Peruvian anchoveta ( Engraulis ringens), weakfish ( Sciaenidae ), cutlassfish ( Trichiuridae ), and anchovy ( Engraulidae ), and cephalopods and mollusks. Sardines ( Clupeidae ), mackerel, and lobster are eaten off Chile, and squid is commonly consumed around the Falkland Islands.
Breeding. The South American Fur Seal has the same general polygynous breeding system as described for the Northern Fur Seal ( Callorhinus ursinus ). For South American Fur Seals, breeding season is from mid-October through mid-January, and timing may differ among colonies in Peru and those in Chile and the Atlantic Ocean. On Uruguayan islands, males may hold territories for as long as 60 days, and mate with up to 13 females. Sexual maturity for females is reached at c.4 years of age. Seven to ten days after postpartum, the female enters estrus. Time spent by lactating females on foraging trips and nursing offspring differs depending on location and availability of prey. In Uruguay, amount of time that females spend on shore depends on weather. When itis hot, they tend to stay in or near water, but during storm events, they may remain ashore. Young are nursed for 8-24 months before being fully weaned, and females may nurse a yearling and a neonate simultaneously. When food resources are scarce, such as during El Nino events, survival rates for young can be extremely low. Failure to produce offspring has been recorded at some rookeries. High mortality rates of young can also occur in densely packed rookeries and in areas subject to powerful storms. Life span of the South American Fur Seal is unknown; an individual lived 15 years in captivity.
Activity patterns. Most of what is known about activities of Southern Fur Seals comes from their time spent ashore during the breeding season. At sea, they may travel or raft together in groups and groom, rest, and feed as described for the Antarctic Fur Seal. Groups frequently gather in the water just offshore of the rookery. When swimming rapidly, they may “porpoise,” or leap clear of the surface. Adult female South America Fur Seals were recorded diving to 29 m, with a maximum of 170 m; average dive time was 2-5 minutes, with a maximum of seven minutes.
Movements, Home range and Social organization. Twelve rookeries of South American Fur Seals are located on islands off Argentina, some of which are used for breeding and others for winter haul-outs. Individuals in Patagonia on the Argentine coast are tied to colonies off Uruguay. Because young are rarely born in Patagonia, the recent increased population there is likely the result of migration from Uruguayan islands. A similar exchange may take place in Tierra del Fuego among rookeries on Argentina’s Staten Island and those in Chile by means of the Beagle Channel. Ten breeding sites of South American Fur Seals occur on the Falkland Islands. Little is known about movements of South American Fur Seals at sea. Individuals routinely reach the southern coast of Brazil, and vagrants have been recorded as far north as coastal Colombia and as far west as the Juan Fernandez Islands.
Status and Conservation. CITES Appendix II. Classified as Least Concern on The IUCN Red Lust. Total population of the South American Fur Sealis ¢.250,000-300,000 individuals, and the majority inhabit Uruguay, where the Uruguayan islands population is stable or increasing. There are ¢.5000-20,000 South American Fur Seals in the Falkland Islands. The Peruvian estimate of 11,400 individuals may be low because the census was conducted during an El Nino year, which usually results in a reduced population there. The population in Chile has been in decline, falling from 102,000 individuals to ¢.30,000 individuals. The small population in Patagonia, Argentina, is increasing ¢.8% /year. South American Fur Seals were subject to unsustainable hunting by sealers in the 19" century, which led to population crashes. Relatively modest numbers of South American Fur Seals are still taken for human consumption in Peru and Chile, and beached carcasses can have bullet wounds. Commercial fisheries may be negatively affecting fish populations sought by South American Fur Seals and are a source of gear entanglements and lethal bycatch. South American Fur Seals have been illegally hunted for use as bait in the king crab fishery in Chile and incidentally caught in shark nets in Uruguay. The limited number of large, dense breeding aggregations could make the South American Fur Seal particularly sensitive to disease epidemics. All species of fur seals depend on their thick coats for thermoregulation and are especially vulnerable to oil spills. Climate change could result in a decline of South American Fur Seals in the Pacific Ocean if El Nino events come more frequently or are intensified.
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Bibliography. Armnould (2009), Baylis et al. (2005), Berta & Churchill (2012), Bonner (1981), Campagna (2008a), Dassis et al. (2012), Jefferson et al. (2008), Lima & Paez (1995), Majluf (1987), Majluf & Trillmich (1981), Naya et al. (2002), de Oliveira & Brownell (2014), de Oliveira, Arias-Schreiber et al. (2006), de Oliveira, Hoffman et al. (2008), Phillips & Stirling (2000), Reeves & Mead (1999), Reijnders et al. (1993), Rice (1998), Trillmich et al. (1986), Vaz-Ferreira & Ponce de Leon (1984), Wickens & York (1997).
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