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Proc Biol Sci. 2007 Oct 22;274(1625):2587-93.

Mass-dependent predation risk and lethal dolphin-porpoise interactions.

Author information

  • 1Department of Environmental and Evolutionary Biology, Institute of Biological and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, UK. r.macleod@bio.gla.ac.uk

Abstract

In small birds, mass-dependent predation risk (MDPR) is known to make the trade-off between avoiding starvation and avoiding predation dependent on individual mass. This occurs because carrying increased fat reserves not only reduces starvation risk but also results in a higher predation risk due to reduced escape flight performance and/or the increased foraging exposure needed to maintain a higher body mass. In principle, the theory of MDPR could also apply to any animal capable of storing energy reserves to reduce starvation and whose escape performance decreases with increasing mass. We used a unique situation along certain parts of coastal Britain, where harbour porpoises (Phocoena phocoena) are pursued and killed but crucially not eaten by bottlenose dolphins (Tursiops truncatus), to investigate whether a MDPR effect can occur in non-avian species. We show that where high levels of dolphin 'predation' occur, porpoises carry significantly less energy reserves than would otherwise be expected and this equates to reducing by approximately 37% the length of time that a porpoise could survive without feeding. These results provide the first evidence that a mass-dependent starvation-predation risk trade-off may be a general ecological principle that can apply to widely different animal types rather than, as is currently thought, only to birds.

PMID:
17698485
[PubMed - indexed for MEDLINE]
PMCID:
PMC2275888
Free PMC Article

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