Arctocephalus pusillus (Schreber, 1775)
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publication ID |
https://doi.org/ 10.5281/zenodo.6604474 |
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DOI |
https://doi.org/10.5281/zenodo.6604524 |
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persistent identifier |
https://treatment.plazi.org/id/965C87FE-1E5B-5647-9CC4-981286ECFDD9 |
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treatment provided by |
Diego |
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scientific name |
Arctocephalus pusillus |
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Afro-Australian Fur Seal
Arctocephalus pusillus View in CoL
French: Otarie du Cap / German: Siidafrika-Seebar / Spanish: Lobo marino de El Cabo
Other common names: Brown Fur Seal; Cape Fur Seal, South African Fur Seal (pusillus); Australian Fur Seal, Tasmanian Fur Seal, Victorian Fur Seal (doriferus)
Taxonomy. Phoca pusilla Schreber, 1775 ,
no type locality given.
The two subspecies, pusillus (Africa) and doriferus (Australia) are genetically similar, indicating the population split relatively recently into the two groups found today. The Australian subspecies was formerly considered to be two species, A. doriferus and A. tasmanicus. Two subspecies recognized.
Subspecies and Distribution.
A.p.pusillusSchreber,1775—coastalSAfrica,fromAngolatoAlgoaBayinSouthAfrica.
A. p. doriferus Wood Jones, 1925 — coastal SE Australia, including Kangaroo I, through Victoria and New South Wales, as well as Tasmania and the Bass Strait. View Figure
Descriptive notes. Total length 200-230 cm (males) and 120-160 cm (females); weight average 274 kg, but up to 353 kg (males) and 57 kg, up to 107 kg (females); newborns 60-70 cm and 6 kg for the “South African Fur Seal” (A. p. pusillus ). Total length 200-230 cm (males) and 136-171 cm (females); weight average 279 kg, but up to 360 kg (males) and 78 kg, up to 110 kg (females); newborns 60-80 cm and 5-12 kg for “Australian Fur Seal” (A. p. doriferus). Dental formula I 3/2, C 1/1, PC 6/5 (x 2) = 36. The two subspecies are similar in morphology and behavior, although Australian Fur Seals are on average slightly heavier than South African Fur Seals. The Afro-Australian Fur Seal is the largest and said to be the most sea lion-like of the fur seals. They are sexually dimorphic, with adult males reaching 3-5 to nearly 4-5 times the weight of females and 1-3-1-9 times their length. They have some resemblance to sea lions. Large head is broad, and crown is more round in males and more flattened in females. Male’s forehead noticeably slopes. Muzzle is long and wide, ending in large nose that overhangs jaws. Long ear pinnae are conspicuous and can be naked in old individuals. Pale vibrissae are of medium length, often reaching to ears. Males have well-developed shoulders, with mane of long guard hairs from nape to chest. 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. South African Fur Seals are usually darker in color than Australian Fur Seals. Furis gray-brown with buff to ginger highlights above, and pale ruddy brown on abdomen. Males become darker as they mature and are generally darker than females. Guard hairs appear grizzled on males. Females and subadults can have paler fur on chests than males. Muzzle often looks pale where vibrissae originate, as do bases of ear pinnae. Neonates have mostly black coats, with silver tints, and may be pale below. At 4-5 months of age, young molt to a gray-brown coat and molt again a year later to a silver-gray coat.
Habitat. Coastal waters and deeper waters of continental shelves and slopes. South African Fur Seals breed on the mainland and islands, and Australian Fur Seals breed on islands in the Bass Strait. Australian Fur Seals favor rocky habitat when ashore. Predators include great white sharks (Carcharodon carcharias) and Killer Whales (Orcinus orca). Jackals ( Canidae ) and hyenas ( Hyaenidae ) are predators at mainland rookeries of South African Fur Seals.
Food and Feeding. Diets of Afro-Australian Fur Seals are varied. Australian Fur Seals prey on species near the sea bottom, such as octopus, squid, barracouta (7hyrsites atun), redbait (Emmelicthys nitidus), greenback horse mackerel (Trachurus declivis), arrow squid (Nototodarus gouldi), and red codling (Pseudophycis bachus). South African Fur Seals consume mid-water and near-surface species, mainly fish such as Cape hake (Merluccius capensis), mackerel, pelagic goby (Sufflogobius bibarbatus), sardines, and anchovy ( Engraulidae ), with some cephalopods (squid) and crustaceans (rock lobster, shrimps, prawns, and amphipods). South African Fur Seals have been known to eat jackass penguins (Spheniscus demersus) and seabirds.
Breeding. The Afro-Australian Fur Seal has the same general polygynous breeding system as described for the Northern Fur Seal ( Callorhinus ursinus ). Female South African Fur Seals and female Australian Fur Seals attain sexual maturity at 3-6 years of age and males at 9-12 years. Breeding season runs from late October to early January. Size of the territories held by males is 62 m* on average and contains about nine females. Annual pregnancy rates are more than 70%, and gestation lasts 51 weeks, including a three-month pause due to delayed implantation. Females bear young within 1-5-2 days after arriving at the rookery. Births peak in early December. Eight or nine days after giving birth, females enter estrus. Length of female foraging trips increases later in the season, from an average of 3-7-6-8 days. Foraging trips of South African Fur Seals tend to be shorter than those of Australian Fur Seals,likely due to better access to food resources in a more productive marine environment. Length of nursing bouts remains steady at an average of 1-7 days. Young are weaned at 10-12 months old, although some are nursed until they are 2-3 years old. Life span for South African Fur Seals is estimated to reach 25 years for a small percentage of individuals. A captive female lived 19 years. Life span for Australian Fur Seals is unknown.
Activity patterns. At sea, both subspecies may be found singly or in small groups, congregating in large rafts just offshore of colonies, and they groom, rest, and feed as described for the Antarctic Fur Seal. They are capable of “porpoising,” leaping in low arcs in the air, when swimming at high speed. Lactating Australian Fur Seals reach depths of 65-85 m during dives lasting 2-3-7 minutes; maximum dives reach 164 m and last up to 8-9 minutes. A significant amount of time is spent foraging during the day, rather than feeding nocturnally. Lactating female South African Fur Seals dive to depths of 41-49 m; maximum dives are 191-204 m.
Movements, Home range and Social organization. Both subspecies are non-migratory, generally staying in waters of their continental shelves. Nevertheless, South African Fur Seals have been sighted up to 220 km offshore, and Australian Fur Seals may travel as much as 160 km offshore. About 75% of South African Fur Seals breed at three rookeries: Atlas Bay-Wolf Bay-Long Islands, Kleinzee, and Cape Cross. More than 50% of Australian Fur Seals breed at two rookeries: Lady Julia Percy Island and Seal Rocks. Vagrants have reached as far north as the Equator on the Atlantic coast of Gabon and south to the subantarctic Prince Edward Islands.
Status and Conservation. CITES Appendix II. Classified as Least Concern on The IUCN Red List. Neither subspecies has been assessed independently on The IUCN Red List. Population size of the South African Fur Seal is ¢.20 times that of the Australian Fur Seal. Two million South African Fur Seals breed at 23 rookeries; 92,000 Australian Fur Seals breed at nine rookeries. These populations are stable or increasing, after declines due to commercial hunting from the 17" to 19" centuries, although neither subspecies was brought to the brink of extinction. The South African Fur Seal appear to have made a stronger recovery than the Australian Fur Seal. Humans have been hunting South African Fur Seals for at least 130,000 years, based on archeological evidence, and annual harvesting of ¢.85,000 young continues today in Namibia. Commercial harvesting ended in South Africa in 1990, but the South African Fur Sealis at risk from lethal fishing-gear entanglements. Rate of entanglement is estimated to be as high as 0-6%. The South African Fur Seal also has colonies close to oil-tanker traffic, making it vulnerable to potential spills. South African Fur Seals hauling-out on the mainland have contact with terrestrial carnivores, exposing them to contagious diseases. Currently, there are no commercial harvests of Australian Fur Seals, but they do come into conflict with fisheries, putting them at risk of gear entanglement and illegal shooting.
Bibliography. Arnould (2009), Arnould & Hindell (2001), Arnould et al. (2003), Berta & Churchill (2012), Bonner (1981), Brothers & Pemberton (1990), de Bruyn et al. (2003), David (1987), De Villiers & Roux (1992), Gamel et al. (2005), Hofmeyr & Gales (2008), Jefferson et al. (2008), Kerley (1983b), Kirkwood & Arnould (2012), Kirkwood & Goldsworthy (2013), Kirkwood, Gales et al. (2005), Kirkwood, Pemberton et al. (2010), Lancaster, Arnould & Kirkwood (2010), Pemberton & Gales (2004), Pemberton & Kirkwood (1994), Pemberton et al. (1992), Reijnders et al. (1993), Rice (1998), Shaughnessy (1980), Thibault (1999), Warneke (1995), Warneke & Shaughnessy (1985), Wickens & York (1997), Wickens et al. (1992), Wynen et al. (2001).
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