MEPS 548:233-247 (2016)  -  DOI:

Drivers of intrapopulation variation in resource use in a generalist predator, the macaroni penguin

C. Horswill1,2,6,*, J. Matthiopoulos2, N. Ratcliffe1, J. A. Green3, P. N. Trathan1, R. A. R. McGill4, R. A. Phillips1, T. C. O’Connell5

1British Antarctic Survey, Natural Environment Research Council, High Cross, Cambridge, CB3 0ET, UK
2Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
3School of Environmental Sciences, University of Liverpool, Liverpool, L69 3GP, UK
4NERC Life Sciences Mass Spectrometry Facility, Scottish Universities Environmental Research Center, East Kilbride, G75 0QF, UK
5Department of Archaeology & Anthropology, University of Cambridge, Cambridge, CB2 3DZ, UK
6Present address: British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU, UK
*Corresponding author:

ABSTRACT: Intrapopulation variation in resource use occurs in many populations of generalist predators with important community and evolutionary implications. One of the hypothesised mechanisms for such widespread variation is ecological opportunity, i.e. resource availability determined by intrinsic constraints and extrinsic conditions. In this study, we combined tracking data and stable isotope analysis to examine how breeding constraints and prey conditions influenced intrapopulation variation in resource use in a generalist predator, the macaroni penguin Eudyptes chrysolophus. Isotopic variation was also examined as a function of breeding success, individual traits and individual specialisation. Variation in isotope ratios was greatest across multiple tissue types when birds were able to undertake mid-range foraging trips (i.e. during incubation and pre-moult). This variation was highly consistent between years that spanned a 3-fold difference in local prey Euphausia superba density, and was also highly consistent at the individual level between 2 years that had similar prey densities. Furthermore, by comparing our results with previous work on the same population, it appeared that a decrease in local prey availability can also increase intrapopulation variation in resource use during periods with more restricted foraging ranges (i.e. during brood-guard and crèche). This study highlights the importance of considering ecological interactions that operate on multiple spatio-temporal scales when examining the drivers of resource use in populations of generalist predators.

KEY WORDS: Central-place constraint · Diet · Foraging range · Habitat use · Intrapopulation variation · Individual specialisation · Seabird · Stable isotope analysis

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Cite this article as: Horswill C, Matthiopoulos J, Ratcliffe N, Green JA and others (2016) Drivers of intrapopulation variation in resource use in a generalist predator, the macaroni penguin. Mar Ecol Prog Ser 548:233-247.

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