How do foragers decide when to leave a patch? A test of alternative models under natural and experimental conditions.
Marshall, Harry H.
Carter, Alecia J.
Rowcliffe, J. Marcus
Journal of Animal Ecology
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A forager's optimal patch-departure time can be predicted by the prescient marginal value theorem (pMVT), which assumes they have perfect knowledge of the environment, or by approaches such as Bayesian updating and learning rules, which avoid this assumption by allowing foragers to use recent experiences to inform their decisions. In understanding and predicting broader scale ecological patterns, individual-level mechanisms, such as patch-departure decisions, need to be fully elucidated. Unfortunately, there are few empirical studies that compare the performance of patch-departure models that assume perfect knowledge with those that do not, resulting in a limited understanding of how foragers decide when to leave a patch. We tested the patch-departure rules predicted by fixed rule, pMVT, Bayesian updating and learning models against one another, using patch residency times (PRTs) recorded from 54 chacma baboons (Papio ursinus) across two groups in natural (n = 6175 patch visits) and field experimental (n = 8569) conditions. We found greater support in the experiment for the model based on Bayesian updating rules, but greater support for the model based on the pMVT in natural foraging conditions. This suggests that foragers may place more importance on recent experiences in predictable environments, like our experiment, where these experiences provide more reliable information about future opportunities. Furthermore, the effect of a single recent foraging experience on PRTs was uniformly weak across both conditions. This suggests that foragers' perception of their environment may incorporate many previous experiences, thus approximating the perfect knowledge assumed by the pMVT. Foragers may, therefore, optimize their patch-departure decisions in line with the pMVT through the adoption of rules similar to those predicted by Bayesian updating.
Natural Environment Research Council (NERC)
Fenner School of Environment and Society
Animal Behavior Society (USA)
International Primatological Society
Explorers Club Exploration Fund
This is the peer reviewed version of the article which has been published in final form at DOI: http://dx.doi.org/10.1111/1365-2656.12089. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
© 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.
Vol. 82, pp. 894 - 902
Place of publication