An assessment of the impact of predation by Cape fur seals Arctocephalus pusillus pusillus on seabirds at Dyer Island, South Africa
At Dyer Island, South Africa, observations of predation of seabirds by Cape Fur Seals Arctocephalus pusillus pusillus were made during 2004 and 2006/07. It was estimated that seals killed about 7% of adult African Penguins Spheniscus demersus annually. This may have contributed
to the penguin colony not increasing in spite of food becoming more available in its vicinity during an eastward shift of epipelagic fish resources off South Africa at the start of the twenty-first century. Adult penguins were most susceptible to mortality in the breeding season as they returned
to feed chicks in the evening. Seals also killed substantial numbers (3–9%) of Cape Cormorant Phalacrocorax capensis fledglings as they left the island, mostly in the morning. The losses of Cape Cormorant fledglings accounted for about 95% of the overall mortality of seabirds
attributable to seals. Mortality inflicted by seals on adults of four species of cormorant was negligible and no predation by seals on gulls and terns was observed.
Keywords: African Penguin; Cape Cormorant; Cape fur seal; Crowned Cormorant; White-breasted Cormorant; predation mortality
Document Type: Research Article
Affiliations: 1: Branch Oceans and Coasts, Department of Environmental Affairs, PO Box 52126, Cape Town, 8000, South Africa 2: CapeNature, 16 Seventeenth Avenue, Voëlklip, Hermanus, 7200, South Africa 3: Animal Demography Unit, Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa
Publication date: 01 December 2013
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