oa South African Journal of Wildlife Research - 24-month delayed open access - Seabird predation by white shark, , and Cape fur seal, , at Dyer Island : research article

Volume 36, Issue 1
  • ISSN : 2410-7220
  • E-ISSN: 2410-8200



Both the white shark (<I>Carcharodon carcharias</I>) and Cape fur seal (<I>Arctocephalus pusillus pusillus</I>) prey on and/or attack seabirds in South Africa. The Dyer Island region abounds in these predators, as well as seabirds, including the African penguin (<I>Spheniscus demersus</I>), Cape cormorant (<i.Phalacrocorax capensis</I>), bank cormorant (<I>P. neglectus</I>), white-breasted cormorant (<I>P. carbo</I>), and crowned cormorant (<I>P. coronatus</I>). Between August 1999 and February 2001, predatory interactions among these taxa were quantified and qualified by the routine collection and inspection of seabird carcasses and injured birds, as well as opportunistic observations of live attacks. White sharks are infrequent predators of seabirds at Dyer Island, perhaps due to an abundance of Cape fur seals (a preferred prey), antipredator behaviour by penguins, and seabirds not being a preferred prey type.Cape fur seals were more conspicuous seabird predators, each year attacking adult penguins (1.99-2.52%), white-breasted cormorants (5.21-5.72%), and crowned cormorants (3.13%), as well as a single bank cormorant. Cape fur seals killed an estimated 0.83-1.09% of the fledgling Cape cormorants. Attacks on penguins at the island are crepuscular as birds depart to and return from foraging grounds. Fledgling Cape cormorants are frequently attacked when alighting on water following disturbance and failed flight attempts, or for bathing.Human disturbance, which may force birds to take to the water, may cause inter-annual differences in the predation impact on this taxon.

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