BRANTA — Richard Inger
Factors affecting prey choice in a despotic herbivore
Institution: University of Glasgow, U.K.
Supervisors: S Bearhop, G Ruxton, K Colhoun (WWT)
Details: PhD 2006 (Completed)
Address: Graham Kerr Building, University of Glasgow, Glasgow (Apr 2006) Email
Subject Keywords: Individuals, stable isotopes, family groups, resource depletion, habitat switch
Species Keywords: (Light-bellied) Brent Goose Branta bernicla
Ideal free models predict that animals should move to food patches where their intake rate is highest. However such models do not consider the implications of group living, including competition, dominance and social rank. For despotic species these effects can be particularly strong, with dominant individuals and groups expected to monopolise the best resources. To test this, we must accurately quantify resource utilisation of individual animals, which is problematical in natural situations. However recent advances in the use of stable isotope analysis have removed many previous constraints.Light-bellied Brent Geese are particularly suited to this type of study, being despotic in nature and foraging in habitats (marine and terrestrial) with particularly robust isotopic gradients. Using stable isotopes ratio of Carbon and Nitrogen (expressed as d13C and d15N) from the tissues of geese, we take advantage of these gradients to determine dietary choice of individuals. This is coupled with field observations to determine both social rank of individuals and groups, and mechanisms driving the maintenance of dominance. This approach allows us to describe resource partitioning amongst social groups with some surprising results, highlighting the costs of living in a group and raising a family.
Inger, R., Bearhop, S, Robinson, J.A., & Ruxton, G. (In press) Prey choice affects the trade-off balance between predation and starvation in an avian herbivore. Animal Behaviour