Diet overlap between harbour porpoise and bottlenose dolphin: An argument in favour of interference competition for food?

Type Article
Date 2006-10
Language English
Author(s) Spitz Jérôme1, 2, Rousseau Yann1, Ridoux Vincent1, 3
Affiliation(s) 1 : Univ La Rochelle, Inst Littoral & Environm, Ctr Rech Mammiferes Marins, F-17000 La Rochelle, France.
2 : Ecole Prat Hautes Etud, Lab Biogeog & Ecol Vertebres, F-34060 Montpellier, France.
3 : Univ La Rochelle, CNRS, IFREMER, Ctr Rech Ecosyst Littoraux Anthropises,UMR 6217, F-17042 La Rochelle, France.
Source Estuarine, Coastal and Shelf Science (0272-7714) (Elsevier), 2006-10 , Vol. 70 , N. 1-2 , P. 259-270
DOI 10.1016/j.ecss.2006.04.020
WOS© Times Cited 79
Keyword(s) North Eastern Atlantic, Tursiops truncatus, Phocoena phocoena, Diet, Top predator, Interference competition
Abstract In aquatic ecosystems, competitive interactions are occasionally described. Violent attacks on harbour porpoises by bottlenose dolphins were reported and it was proposed that this behavior could result from competitive interactions for food. This hypothesis implies that the two predators should share all or part of they prey range. In this work, we describe the diets of each predator in the Bay of Biscay and adjacent areas from stomach content analysis of stranded animals. The diet of the harbour porpoise was mostly composed of small schooling fish living close to the seafloor (98 percent by mass). The diet of the bottlenose dolphin was characterised by the presence of large specimens of demersal fish (91 percent by mass) and cephalopods. Several prey species are common in the two diets and even the length distributions of some of them, such as sardine or scads, are very similar. However, global indices such as the Mantel test or the Pianka's index indicate no or weak overlap. The dietary results suggest that the two predators show partial dietary overlap over several major dimensions of the foraging niche: prey profile, foraging habitats, prey species and size range. We suggest interference competition is plausible at the scale of a prey school that would be exploited jointly by groups of the two predators. (c) 2006 Elsevier Ltd. All rights reserved.
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