The effect of prey density on predators: Conspicuousness and attack success are sensitive to spatial scale

Morrell, Lesley�J.; Ioannou, Christos C.; Ioannou, Christos�C.; Morrell, Lesley J.; Ruxton, Graeme�D.; Ruxton, Graeme D.; Krause, Jens

Abstract

In contrast to the numerous studies that have examined the response of predators to prey group size, little is known about how prey density affects prey detection and the accuracy of attacks. We demonstrate that increasing the density of Daphnia magna swarms increases conspicuousness to a natural predator, the three-spined stickleback. Denser areas of groups were more conspicuous, as the fish attacked prey in denser parts of the group than would be expected if they attacked the nearest prey upon entering the feeding chamber. The spatial error of attacks also increased with the density around the target; hence, different stages of predation (searching for vs. successfully attacking prey) seem to select for opposing responses to prey density. However, whereas the effect of density on target selection only occurred using a global measure of density (average interindividual distance), the effect on attack error was only significant using a local measure of density (Voronoi polygon area). We believe this effect of spatial scale reflects the reduction in the number of prey in the visual field of the predator as an attack progresses, providing a perceptual basis for the importance of spatial scale in density-dependent processes.

Citation

Ioannou, C. C., Morrell, L. J., Ruxton, G. D., & Krause, J. (2009). The effect of prey density on predators: Conspicuousness and attack success are sensitive to spatial scale. The American naturalist, 173(4), 499-506. https://doi.org/10.1086/597219

• Journal Article Type: Article
• Acceptance Date: Sep 24, 2008
• Online Publication Date: Feb 20, 2009
• Publication Date: Apr 1, 2009
• Journal: AMERICAN NATURALIST
• Print ISSN: 0003-0147
• Electronic ISSN: 1537-5323
• Publisher: University of Chicago Press
• Peer Reviewed: Peer Reviewed
• Volume: 173
• Issue: 4
• Pages: 499-506
• DOI: https://doi.org/10.1086/597219
• Keywords: Ecology, Evolution, Behavior and Systematics
• Public URL: https://hull-repository.worktribe.com/output/409420