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Optimal individual positions within animal groups

Morrell, Lesley; Romey, William L.


William L. Romey


Animal groups are highly variable in their spatial structure, and individual fitness is strongly associated with the spatial position of an animal within a group. Predation risk and food gains are often higher at the group peripheries; thus, animals must trade-off predation costs and foraging benefits when choosing a position. Assuming this is the case, we first use simulation models to demonstrate how predation risk and food gains differ for different positions within a group. Second, we use the patterns from the simulation to develop a novel model of the trade-off between the costs and the benefits of occupying different positions and predict the optimal location for an animal in a group. A variety of testable patterns emerge. As expected, increasing levels of satiation and vulnerability to predators and increasing predation risk result in increased preferences for central positions, likely to lead to increased competition or more tightly packed groups. As food availability increases, individuals should first prefer center positions, then edge, and returning to central positions under highest food levels. Increasing group size and/or density lead to more uniform preferences across individuals. Finally, we predict some situations where individuals differing in satiation and vulnerability prefer a range of different locations and other situations where there is an abrupt dichotomy between central and edge positions, dependent on the levels of monopolization of food by peripheral individuals. We discuss the implications of our findings for the structure of groups and the levels of competition within them and make suggestions for empirical tests.


Morrell, L., & Romey, W. L. (2008). Optimal individual positions within animal groups. Behavioral ecology, 19(4), 909-919.

Journal Article Type Article
Acceptance Date Apr 9, 2008
Online Publication Date May 16, 2008
Publication Date 2008-07
Deposit Date Feb 20, 2017
Publicly Available Date Feb 20, 2017
Journal Behavioral ecology
Print ISSN 1045-2249
Electronic ISSN 1465-7279
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 19
Issue 4
Pages 909-919
Keywords Competition, Group living, Group structure, Optimization, Simulation model
Public URL
Publisher URL
Additional Information This is the author's accepted manuscript of an article published in Behavioral ecology, 2008, v.19 issue 4.


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