title: Mass-dependent predation risk and lethal dolphin-porpoise interactions.
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.
authors: Department 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
authors: R
authors: R
authors: MacLeod
authors: C D
authors: CD
authors: MacLeod
authors: J A
authors: JA
authors: Learmonth
authors: P D
authors: PD
authors: Jepson
authors: R J
authors: RJ
authors: Reid
authors: R
authors: R
authors: Deaville
authors: G J
authors: GJ
authors: Pierce
mesh_terms: D000818:Animals; D001835:Body Weight; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D004734:Energy Metabolism; D005260:Female; D008297:Male; D050741:Phocoena / Q000502:physiology*; D011235:Predatory Behavior / Q000502:physiology*; D013217:Starvation; D006113:United Kingdom
references: Proc Biol Sci. 1998 Jul 7;265(1402):1167-70
references: 9699310
references: Vet Rec. 1998 Nov 28;143(22):614-5
references: 9871957
references: Proc Biol Sci. 2001 Mar 7;268(1466):487-91
references: 11296860
references: Comp Biochem Physiol A Mol Integr Physiol. 2001 Dec;131(1):169-82
references: 11733175
references: J Exp Biol. 2003 Feb;206(Pt 4):667-74
references: 12517984
references: Philos Trans R Soc Lond B Biol Sci. 1993 Apr 29;340(1291):73-92
references: 8099746
references: Proc Biol Sci. 1997 Jan 22;264(1378):89-94
references: 9061964