. Predation on Australian sea lions Neophoca cinerea by white sharks Carcharodon carcharias in South Australia

Abstract

From January 1988 to December 2002, 182 Australian sea lions Neophoca cinerea with injuries attributable to white sharks Carcharodon carcharias were recorded in the N. cinerea colony at Seal Bay, Kangaroo Island. The mean number per month was 1.0 (s.d. 1.3), and the number per calendar year varied from 5 to 25 (mean 12.1, s.d. 6.1). The incidence was highest in summer (December to February) and autumn (March to May). The month with the greatest incidence of injured sea lions was January, when it was 17% of the total. This coincides with the higher proportion of white shark records around Kangaroo Island in summer and autumn than in other seasons (Bruce 1992). Adult female and juvenile sea lions were attacked most frequently, with 38% and 26%, respectively. Adult females pass through the waters near the colony more frequently than other sea lions, which makes them more susceptible than other age-sex groups to attacks by white sharks. Most (42%) injuries were to the head and central parts of the sea lions' bodies and 39% were to the rear of their bodies ('rear trunk' and 'hind flippers' areas). The stomach contents of a white shark caught in a bottom-set monofilament gill-net at Cape Gantheaume, Kangaroo Island in April 1992 included two N. cinerea pups aged 10-12 months. They formed about 75% of the shark?s stomach contents.