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Arctocephalus pusillus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CARNIVORA OTARIIDAE

Scientific Name: Arctocephalus pusillus
Species Authority: (Schreber, 1775)
Common Name/s:
English Afro-Australian Fur Seal, Cape Fur Seal, Brown Fur Seal, South African Fur Seal
French Arctocéphale D'Afrique Du Sud
Taxonomic Notes: Two subspecies are recognized:
Arctocephalus pusillus pusillus: Cape Fur Seal
Arctocephalus pusillus doriferus: Australian Fur Seal

The two recognized subspecies of Arctocephalus pusillus are almost identical in both anatomy and behaviour (Warnecke and Shaughnessy 1985). Repenning et al. (1971) accorded them subspecific status based on one cranial character and separate geographic ranges. Very low genetic divergence indicates that they split relatively recently, with the Australian subspecies being the more recently established (Lento et al. 1997, Wynen et al. 2001). Australian Fur Seals have previously been named A. forsteri, A. doriferus, and A. tasmanicus (Repenning et al. 1971).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor/s: Hofmeyr, G. & Gales, N. (IUCN SSC Pinniped Specialist Group)
Reviewer/s: Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Justification:
Due to their large population sizes, the global Cape Fur Seal (Afro-Australian Fur Seal) population appears to be healthy, and the subspecies should both therefore be classified as Least Concern (LC). However, current hunting levels might not be sustainable in Namibia, given low pup production levels during several recent years and hence this species should be reviewed again within a decade.

Geographic Range [top]

Range Description: Cape Fur Seals haul out along the mainland and coastal islands of southwestern and southern Africa, from Ilha dos Tigres in Angola to Algoa Bay in South Africa (Kirkman et al. 2007). Vagrants have been sighted on the coasts of Gabon (Thibault 1999) and the Prince Edward Islands (Kerley 1983). Australian Fur Seals breed on islands of the Bass Strait (Warnecke 1995) but range the waters off the coasts of South Australia, Tasmania, Victoria and New South Wales (Pemberton and Gales 2004). While both subspecies do not travel far from their continental shelves, Cape Fur Seals have been recorded up to 220 km offshore (Shaughnessy 1979).
Countries:
Native:
Angola (Angola); Australia (New South Wales, South Australia, Tasmania, Victoria); Namibia; South Africa (Eastern Cape Province, Marion-Prince Edward Is. - Vagrant, Western Cape)
Vagrant:
Gabon
FAO Marine Fishing Areas:
Native:
Atlantic – southeast; Indian Ocean – eastern; Pacific – southwest
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Estimates indicate that of some 2 million Cape Fur Seals presently breed at some 23 rookeries or rookery groups in 2004 (Kirkman et al. 2007). The population size of this subspecies is believed to have been relatively stable since 1993 (Butterworth et al. 1995, Kirkman et al. 2007). Some 75% of Cape Fur Seals breed at three of these sites: the Atlas Bay-Wolf Bay-Long Islands Group, Kleinzee and Cape Cross. Most other rookeries are estimated to contain more than a 1,000 adults (Kirkman et al. 2007). While the abundances of the larger rookeries are relatively stable, they do experience fluctuations. These fluctuations are greater in Namibian rookeries which have experienced major mortality events due to the impact of poor environmental conditions on prey populations (Roux 1998). Smaller rookeries tend to experience greater fluctuations than larger rookeries (Kirkman et al. 2007).

Some 92,000 Australian Fur Seals were estimated to breed at nine rookeries in 2003 and the population is believed to be increasing. More than half of the population (55%) breed at two of these sites: Lady Julia Percy Island and Seal Rocks. Five other rookeries are estimated to contain more than a 1000 adults. Inter-annual fluctuations are experienced at some rookeries (Kirkwood et al. 2005).
Population Trend: Increasing

Habitat and Ecology [top]

Habitat and Ecology: These two subspecies are the largest of all fur seals. They are also highly sexually dimorphic. Adult male Australian Fur Seals average 2.16 m in length and 279 kg in mass, while adult females are 1.36 –1.71 m in length and attain an average weight of 78 kg. Newborns are 60-80 cm in length and weigh between 5 and 12 kg (Warnecke 1995). Adult male Cape Fur Seals are 2–2.3 m long and average 247 kg in weight. Adult females are 1.2–1.6 m long and weigh an average of 57 kg. At birth they weigh around 6 kg (Shaughnessy 1979).

Females of this species become sexually mature at 3-6 years and males at 9- 12 years. The annual pregnancy rate of mature females is 71 % for Cape Fur Seals (Wickens and York 1997) and 73 % in Australian Fur Seals (Warnecke and Shaughnessy 1985). Gestation lasts 51 weeks, including a three-month delay of implantation. Longevity and adult mortality are unknown (Arnould et al. 2003, Butterworth et al. 1995, Reijnders et al. 1993).

Both subspecies are highly polygynous. Adult males arrive at the colonies first. Breeding is from late October to the beginning of January. Females give birth 1.5–2 days after arrival ashore. The peak of pupping for both subspecies is in the first week of December, although there is some variation between colonies (De Villiers and Roux 1992, Warnecke and Shaughnessy 1985). Females attend the pup for 8-9 days before coming into oestrous, mating, and departing on their first foraging trip (Warnecke and Shaughnessy 1985). Foraging trips get longer as the season progresses from summer to winter, changing from a mean of 3.71 to 6.77 days for Australian Fur Seals. Periods of attendance stay the same from birth to weaning and have a mean length of 1.7 days (Arnould and Hindell 2001). Foraging intervals are shorter for Cape Fur Seals, probably reflecting greater availability of food (Gamel et al. 2005). Pups are usually weaned at 10–12 months even though some pups begin to forage at 7 months, and others are nursed for 2–3 years (Warnecke and Shaughnessy 1985).

Foraging dives by lactating Australian Fur Seal females are usually to 65–85 m with a maximum depth of 164 m, and dives usually last from 2–3.7 minutes, with a maximum duration of 8.9 minutes (Arnould and Hindell 2001). At sea, these seals are found alone or in small groups of up to 15 animals, but they often gather in huge rafts adjacent to rookeries. Neither of the populations is migratory; they tend to move locally within their restricted ranges (Arnould 2002, Oosthuisen 1991, Warnecke and Shaughnessy 1985).

Both subspecies are opportunistic feeders that take a wide variety of prey, including pelagic, mid-water and benthic animals. Australian fur seals feed benthically and take a variety of species of fish, squid, octopus and rock lobsters (Warnecke and Shaughnessy 1985). Cape Fur Seals are principally pelagic foragers. They take cape hake, horse mackerel, pelagic goby, pilchards, anchovy, squid of the genus Loligo, rock lobster, shrimp, prawns, and amphipods (David 1987a, De Bruyn et al. 2003, Mecenero 2006). Cape Fur Seals have also been reported to occasionally take African Penguins and several species of flying seabirds (Crawford et al. 1989).

Predators of the Cape and Australian Fur Seals include Killer Whales and Great White Sharks at sea (Compagno 1989, Pemberton and Kirkwood 1994). The Cape Fur Seal is also preyed upon on shore by Black-backed Jackals and Brown Hyenas in southern Africa (Skinner et al. 1995).
Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): Cape and Australian Fur Seals were hunted heavily during the 17th, 18th and 19th centuries and both populations were reduced to low levels (David 1987b, Warnecke and Shaughnessy 1985). Under protection, both have recovered, although the Cape subspecies to a much greater extent than the Australian subspecies, which has not rebounded to estimated pre-exploitation levels (Kirkwood et al. 2005, Kirkman et al. 2007). Levels of exploitation of Cape Fur Seals were not as severe as that experienced by other species of fur seals and genetic variation remains high (Matthee et al. 2006).

Seal harvests in South Africa were first controlled in 1893 and were suspended in 1990. They continue in Namibia at the mainland colonies of Cape Cross and Wolf and Atlas Bays. The 2006 annual harvest in Namibia was set at 85 000 animals which is made up primarily of pups, but also includes a small percentage of bulls. This high harvest level has been retained despite several years with very high mortality levels for pups along with many thousands of adult deaths in Namibia (Kirkman 2006). This mortality has been attributed to a scarcity of fish and poor marine productivity along the coast of Namibia, which occurs at intervals (Roux 1998).

Cape Fur Seals are sometimes reported to be detrimental to commercial fisheries, both via direct competition and operational interactions. Some seals are taken incidentally in fishing operations every year. A number are also shot illegally during fishing operations (Wickens et al. 1992). More significantly, Cape Fur Seals are known to become entangled in marine debris such as packing bands, discarded lines and nets and other material that can become a collar around an animal’s neck. Rates of entanglement vary by colony, but have been estimated to be between 0.12–0.66 % (Shaughnessy 1980). Conflicts between Australian Fur Seals and local fisheries include seals damaging gear and stealing catch, and becoming entangled in nets and traps (Goldsworthy et al. 2003, Pemberton et al. 1992, Stewardson 2007). While the shooting of seals during fishing operations does occur, it is illegal (Stewardson 2007).

Like all fur seals, Cape and Australian Fur Seals are vulnerable to oil spills because of their dependence on their thick pelage for thermoregulation (Bonner 1978). Cape Fur Seals come in regular contact with a number of species of terrestrial carnivores, and both subspecies are at risk of exposure to viruses and other disease types that could lead to epidemics (Kirkman 2006, Lavigne and Schmitz 1990).

Both subspecies are visited by tourists at a number of colonies. Disturbance is believed to be minimal (Kirkwood et al. 2003)

Conservation Actions [top]

Conservation Actions: Australian Fur Seals are protected nationally by the Environment Protection and Biodiversity Conservation Act (1999). They are also protected in all states in which they occur by state-specific legislation (Stewardson 2007). Australian Fur Seals are included in national strategies on seals published in 1999 (Shaughnessy 1999) and 2007 (DAFF 2007).

Although Cape Fur Seals have been protected in South Africa since 1893, they were still subject to government run or government authorized commercial harvests to 1990 (Butterworth et al. 1995, Wickens et al. 1991). The Sea Birds and Seals Protection Act of 1973 (SBSPA), provides broad protection for seals in South Africa, but also provides for a harvest if it is deemed desirable. While the conservation and harvesting of seals in Namibia was previously controlled by the SBSPA this has been replaced by the Marine Resources Act (2000) which relaxed restrictions aimed at ensuring a humane harvest (Kirkman 2006).

Listed on CITES Appendix II.
Citation: Hofmeyr, G. & Gales, N. (IUCN SSC Pinniped Specialist Group) 2008. Arctocephalus pusillus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 19 April 2014.
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