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...

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Bibliographic Details
Published in:Ostrich 2013-12, Vol.84 (3), p.191-198
Main Authors: Makhado, Azwianewi B, Crawford, Robert JM, Waller, Lauren J, Underhill, Les G
Format: Article
Language:English
Subjects:
adults
African Penguin
Arctocephalus pusillus
Arctocephalus pusillus pusillus
breeding season
Cape Cormorant
Cape fur seal
chicks
Crowned Cormorant
fish
Laridae
Mortality
penguins
Phalacrocorax
Phalacrocorax capensis
Predation
predation mortality
seabirds
seals
Spheniscus
Spheniscus demersus
White-breasted Cormorant
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Summary: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.
ISSN:1727-947X
0030-6525
1727-947X
DOI:10.2989/00306525.2013.863234