habitat_narrative
Terrestrial|Marine
The Cape Fur Seal and the conspecific Australian Fur Seal are the largest of all the fur seals. They are also highly sexually dimorphic. Adult male Cape Fur Seals are 2â2.3 m long and average 247 kg in weight. Adult females are 1.2â1.6 m long and weigh an average of 57 kg. At birth they weigh around 6 kg (Shaughnessy 1979). Females become sexually mature at 3â6 years and males at 9â12 years (Wickens & York 1997). The annual pregnancy rate of mature females has been estimated at 71% (Wickens & York 1997). Gestation is known to last 51 weeks, including a three-month delay of implantation but longevity and adult mortality are unknown (Reijnders et al. 1993; Butterworth et al. 1995; Wickens & York 1997).Cape Fur Seals are highly polygynous with breeding males defending territories where multiple females gather to pup. Breeding occurs from late October to the beginning of January, with adult males arriving at the colonies first. Females give birth 1.5â2 days after their arrival. The peak of pupping is in the first week of December, although there is some variation between colonies (David 1987a). Mothers attend to their pup for about 6-7 days before coming into oestrous, mating, and departing on their first foraging trip (Rand 1955). From then until the time of weaning, the mothers alternate between regular foraging trips to sea and shore visits to nourish their pups with milk. Pups are usually weaned at 10â12 months of age. The Cape Fur Seal and the Australian Fur Seal differ from other fur seals in that they are highly tolerant of bodily contact (thigmotactism), a behavioural trait that they have in common with sea lions.
Cape Fur Seals are generalist foragers that take a wide variety of pelagic, demersal and benthic prey, including cape hake (Merluccius spp.), horse mackerel (Trachurus spp.), Pelagic Goby (Sufflogobius bibarbatus), pilchards (Sardinops sp.), anchovy, squid of the genus Loligo, rock lobster, shrimp, prawns, and amphipods (David 1987a; de Bruyn et al. 2003; Mecenero et al. 2006; Huisamen et al. 2012). They (primarily rogue males) have also been reported to predate on seabirds, including the African Penguin (Spheniscus demersus) and the Cape Gannet (Morus capensis), both of which are of conservation concern (Crawford et al. 1989).
Great White Sharks (Carcharodon carcharias) (Martin et al. 2005) and Killer Whales (Orcinus orca) (Rand 1955) are predators of the Cape Fur Seal at sea. On shore their pups are preyed upon by Black-backed Jackal (Canis mesomelas) and Brown Hyaenas (Hyena brunnea) (Oosthuizen et al. 1997; Wiesel 2010).
Ecosystem and cultural services: The Cape Fur Seal is the only pinniped breeding in mainland South Africa. As a top predator they most likely have a critical role in prey regulation and the structure and functioning of the ecosystem. This role is difficult to elucidate especially given the complexity of the marine food web, but modelling studies have provided some insight in this regard. While Cape Fur Seals are frequently suggested to be significant competitors with commercial fisheries, modelling has suggested that predation by Cape Fur Seals on predatory fish (for example, hake) could possibly result in greater biomass of target fish available for fisheries, with potential for a net negative impact on the fishery if seal numbers were reduced (Punt & Butterworth 1995).
Changes in numbers, distribution or other characteristics of marine higher predators such as the Cape Fur Seal are frequently symptomatic of changes occurring at lower trophic levels, such as may be caused by effects of overfishing or other environmental (e.g. climatic) changes. Therefore they potentially serve as useful indicators of ecosystem health or changes in marine resources, especially because their habit of hauling out on land makes them accessible to researchers (Kirkman et al. 2011).
The Cape Fur Seal also serves as prey for other predators, including the iconic Great White Shark (Martin et al. 2005). The attractiveness of seal colonies on the southwest coast to Great White Sharks, and associated shark-seal predatory interactions, is important for the commercial success of the Great White Shark viewing ecotourism industry. Cape Fur Seal colonies provide a reliable attraction (unlike more elusive species targeted for tourist viewing such as some whales, dolphins and sharks) and are part of the viewing experience on offer by several ecotourism ventures. Some seal colonies on the mainland can also be viewed by land-based tourists, usually as part of a broader package. Examples are at the Kleinsee colony which is situated in a mining lease and is one of the viewing experiences on offer during mine tours, and the Bird Island Reserve in Lambertâs Bay, where a seal colony is visible from a tourist hide beside the gannetry.
