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Prey body size mediates the predation risk associated with being "odd"

Morrell, Lesley J.; Downing, Beatrice; Rodgers, Gwendolen M.


Beatrice Downing

Gwendolen M. Rodgers


Despite selection pressures on prey animals to maintain phenotypically homogeneous groups, variation in phenotype within animal groups is commonly observed. Although many prey animals preferentially associate with size-matched individuals, a lack of preference or a preference for nonmatching group mates is also commonly observed. We suggest that the assortative response to predation risk may be mediated by body size because larger bodied prey may be at greater risk of predation than smaller bodied prey when in a mixed group due to their greater potential profitability. We test this idea by observing attacks by three-spine sticklebacks Gasterosteus aculeatus on mixed groups of large and small Daphnia magna prey. We find that smaller Daphnia are at greatest risk when they form the majority of the group, whereas larger Daphnia are at the greatest predation risk when they form the minority. Thus, we predict that both large and small prey should benefit by association with large prey, generating a potential conflict over group membership that may lead to the mixed phenotype groups we observe in nature.


Morrell, L. J., Downing, B., & Rodgers, G. M. (2015). Prey body size mediates the predation risk associated with being "odd". Behavioral ecology, 26(1), 242-246.

Journal Article Type Article
Acceptance Date Sep 16, 2014
Online Publication Date Oct 17, 2014
Publication Date 2015
Deposit Date Mar 24, 2015
Publicly Available Date Mar 24, 2015
Journal Behavioral ecology
Print ISSN 1045-2249
Electronic ISSN 1465-7279
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 26
Issue 1
Pages 242-246
Keywords Assortment; Confusion effect; Group living; Oddity effect; Shoaling
Public URL
Publisher URL
Additional Information Author's accepted manuscript of article published in: Behavioral ecology, 2015, v.26, issue 1 at:


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