Southern Fur Seals: Arctocephalus spp

Abstract

Southern fur seals (genus Arctocephalus) are generally recognized as comprising eight species and four subspecies. As the name implies, they occur almost exclusively in the Southern Hemisphere with only one species being found north of the equator. They are circumpolar in distribution, occurring in all the Southern Hemisphere oceans. The majority of southern fur seals were overexploited during large-scale commercial hunting in the eighteenth and nineteenth centuries, and many species were so depleted in numbers that they were considered extinct. Fortunately, because of the isolated nature of the islands on which many southern fur seal species occur, remnant populations persisted. All known species survived and are now recovering at various rates. The most obvious diagnostic feature separating fur seals from sea lions is the presence of an underfur layer in their pelage. The southern fur seals can be distinguished from the northern fur seal, Callorhinus ursinus, by the extent to which the fur line extends on the fore flippers. In the northern fur seal the fur stops at the base of the flippers in a sharp line, whereas in southern fur seals it extends across part of the flipper, ending in a line over the metacarpals. The nonbreeding range of most southern fur seal species is often much greater than the breeding distribution and is determined by the movements of males and juveniles. These segments of the population are not restricted in the same way as adult females, which must return regularly to the natal colony in order to suckle their pup. Southern fur seals feed on a variety of prey species, including fish, cephalopods, crustaceans, and even penguins and other seabirds. The majority of research on foraging behavior in southern fur seals has involved lactating females due to their relative ease of handling and recapture in comparison to adult males. While definitive data are lacking for some species, southern fur seal females generally reach sexual maturity at 3–5 years of age and thereafter have pregnancy rates of 70–80%. Males reach sexual maturity around the same age but do not attain territorial status and the ability to mate until 7–10 years old. In addition to experiencing severe population declines during the eighteenth and nineteenth centuries as a result of the commercial sealing era, several southern fur seal species have been subject to culls and harvests, both legal and illegal, at various times since then. The majority of these have been related to commercial fisheries concerns of competition with increasing seal populations. In contrast to the generally negative impacts of interactions with fisheries, populations of several southern fur seal species have enjoyed positive attention in recent decades through eco-tourism activities.