Dietary divergence is associated with increased intra-specific competition in a marine predator

Ratcliffe, N., Adlard, S., Stowasser, G. and McGill, R. (2018) Dietary divergence is associated with increased intra-specific competition in a marine predator. Scientific Reports, 8, 6827. (doi: 10.1038/s41598-018-25318-7) (PMID:29717229) (PMCID:PMC5931528)

Abstract

Optimal foraging theory predicts that when food is plentiful all individuals should take a small range of preferred prey types, but as competition increases less preferred prey will be included in the diet. This dietary switching may not be uniform among individuals, which produces discrete dietary clusters. We tested this hypothesis for gentoo penguins at Bird Island, South Georgia, using stable isotope analysis and biologging. Competition, in the form of the density of foraging dives, increased markedly from incubation to chick-rearing owing to increased foraging effort. Birds responded behaviourally by exploiting a greater portion of the available foraging radius and increasing dive depths. Dietary niche width doubled and two discrete dietary clusters appeared; one comprising birds that consumed mostly krill and another that ate a greater proportion of demersal fish. There were no differences in morphology between the dietary classes, but birds in the fish class had a tendency to dive deeper, which suggests a behavioural basis for specialization. Our findings are consistent with the hypothesis that intra-specific competition expands the population’s dietary niche width and drives divergence in diets among individuals.

• Item Type: Articles
• Additional Information: This study is part of the British Antarctic Survey Polar Science for Planet Earth Programme, funded by the Natural Environment Research Council. Stable isotope analysis was conducted under a grant awarded by the Scottish Universities Environmental Research Centre node of the NERC Life Sciences Mass Spectrometry Facility in East Kilbride (EK174/01-11).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: McGill, Dr Rona
• Authors: Ratcliffe, N., Adlard, S., Stowasser, G., and McGill, R.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Scientific Reports
• Publisher: Nature Research
• ISSN: 2045-2322
• ISSN (Online): 2045-2322
• Copyright Holders: Copyright © 2018 The Authors
• First Published: First published in Scientific Reports 8:6827
• Publisher Policy: Reproduced under a Creative Commons License