Intergroup variation in stable isotope ratios reflects anthropogenic impact on the Barbary macaques (Macaca sylvanus) of Gibraltar

Mark R. Schurr, Agustín Fuentes, Ellen Luecke, John Cortes, Eric Shaw

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Interactions with humans impact many aspects of behavior and ecology in nonhuman primates. Because of the complexities of the human-nonhuman primate interface, methods are needed to quantify the effects of anthropogenic interactions, including their intensity and differential impacts between nonhuman primate groups. Stable isotopes can be used to quickly and economically assess intergroup dietary variation, and provide a framework for the development of specific hypotheses about anthropogenic impact. This study uses stable carbon and nitrogen isotope analysis to examine intraspecific variation in diet between five groups of Barbary macaques, Macaca sylvanus, in the Upper Rock Nature Reserve, Gibraltar. Analysis of hair from 135 macaques showed significant differences in δ13C and δ15N values between a group with minimal tourist contact and groups that were main tourist attractions. Because we observed no overt physiological or substantial behavioral differences between the groups, feeding ecology is the most likely cause of any differences in stable isotope ratios. Haphazard provisioning by tourists and Gibraltarians is a likely source of dietary variation between groups. Stable isotope analysis and observational data facilitate a deeper understanding of the feeding ecology of the Barbary macaques relevant to the role of an anthropogenic ecology for the species.

Original languageEnglish (US)
Pages (from-to)31-40
Number of pages10
Issue number1
StatePublished - Jan 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Animal Science and Zoology


  • Gibraltar
  • Isotope analysis
  • Macaca sylvanus
  • Provisioning
  • Tourism


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