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Marine Ecology Progress Series

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MEPS 604:251-262 (2018)  -  DOI:

Frequency and consequences of individual dietary specialisation in a wide-ranging marine predator, the northern gannet

Thomas W. Bodey1,2,*, Ian R. Cleasby1, Stephen C. Votier3, Keith C. Hamer4, Jason Newton5, Samantha C. Patrick6, Ewan D. Wakefield4,7, Stuart Bearhop1

1Centre for Ecology & Conservation, University of Exeter, Penryn TR10 9FE, UK
2School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
3Environment & Sustainability Institute, University of Exeter, Penryn TR10 9FE, UK
4School of Biology, University of Leeds, Leeds LS2 9JT, UK
5NERC Life Sciences Mass Spectrometry Facility, Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, UK
6School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK
7Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, UK
*Corresponding author:

ABSTRACT: Individual specialisations in animals are important contributors to a wide range of ecological and evolutionary processes, and have been particularly documented in relation to multiple aspects of foraging behaviours. Central-place foragers, such as seabirds, frequently exhibit pronounced specialisations and individual differences in a variety of foraging traits. In particular, the availability of fisheries discards alongside natural prey resources provides additional potential for differentiation and specialisation for opportunistically scavenging seabird species. However, the consequences of such specialisations for at-sea distributions and intraspecific interactions are not well known. Here, we investigated the links between the degree of dietary specialisation on natural or discarded prey and the foraging movements and spatial occupancy of northern gannets Morus bassanus in relation to differing intraspecific competition at 6 colonies of differing sizes. We found that, at most colonies, individuals with different dietary strategies concentrated foraging at differing levels of intraspecific competition. In addition, individuals pursuing different strategies were frequently, but not consistently, spatially separated, distinctions that were most acutely seen in females. However, this variation in individual strategy had no significant impact on current body condition. These analyses demonstrate how foraging-associated metrics need not covary within an unconstrained system. They also reveal that specialisation can have important consequences for the competitive regimes individuals experience, highlighting the complexity of examining interacting consequences at large spatial scales.

KEY WORDS: Fisheries · Foraging · GPS · Individual specialisation · Stable isotope analysis · Seabird

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Cite this article as: Bodey TW, Cleasby IR, Votier SC, Hamer KC and others (2018) Frequency and consequences of individual dietary specialisation in a wide-ranging marine predator, the northern gannet. Mar Ecol Prog Ser 604:251-262.

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