Unified effects of aggregation reveal larger prey groups take longer to find

Christos C. Ioannou, Frederic Bartumeus, Jens Krause, Graeme D. Ruxton

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)


Previous work has suggested that larger groups of prey are more conspicuous to predators. However, this ignores that prey populations are finite. As groups get larger they become fewer, hence the encounter rate between predator and prey decreases with prey aggregation. Here, we present a two-dimensional model based on visual angle to unify these encounter and conspicuousness effects of aggregation. With experimental support using three-spined sticklebacks (Gasterosteus aculeatus L.), searching for chironomid larvae, we demonstrate that the increase in visual angle with increasing group size is outweighed by its corresponding decrease as the groups become fewer and thus further away from the searching predator. The net effect is that prey are found with more difficulty when they aggregate, giving an additional anti-predatory benefit to group living rather than a cost.

Original languageEnglish
Pages (from-to)2985-2990
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1720
Publication statusPublished - 7 Oct 2011


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