Evol Ecol Res 16: 19-35 (2014)     Full PDF if your library subscribes.

A predator–prey behavioural game: how does number of food patches influence foraging tactics?

Merav W. Katz1, Zvika Abramsky1, Burt P. Kotler2, Inbar Roth1, Ofir Altestein1 and Michael L. Rosenzweig3

1Department of Life Sciences, Ben Gurion University, Beer Sheva, Israel,  2Institute of Desert Research, Ben Gurion University, Sde Boqer, Israel and  3Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, USA

Correspondence: Z. Abramsky, Department of Life Sciences, Ben Gurion University, Beer Sheva 84105, Israel.
e-mail: zvika@bgu.ac.il


Background: When exposed in previous experiments to a behavioural game in a three-pool laboratory theatre, common goldfish, Carassius auratus (the prey), and little egrets, Egretta garzetta (the predator), demonstrated optimal adjustments in their foraging and anti-foraging behaviours when confronted with different numbers of fish.

Question: In a similar theatre with one, two or three pools and a fixed number of fish per pool, will predator and prey again solve the game and optimally adjust their foraging and anti-foraging behaviours?

Methods: Experiments were conducted in two identical, circular aviaries (diameter 7 m) consisting of three circular pools (diameter 1.52 m), each of which could be covered so as to remove it from an experiment. We conducted experiments with one, two or three uncovered pools. Each pool had two available fish habitats: protected from predation but without food for fish, and exposed but with food. There were 15 goldfish in each experimental pool. One egret foraged in each aviary (none in controls). The egret moved at will among the pools. During six-hour observation periods, we observed, minute-by-minute, the distribution of fish among their habitats and the movement of the egret among the pools. In addition to compiling summary statistics of the behaviours, we counted the number of successful predation events and analysed the results to test their optimality.

Results: As the number of pools changed, the egret changed its foraging behaviour, moving among the pools in a way that maximized its capture success. The time an egret spent hunting correlated with the number of pools available, thus it captured fish at a higher rate when more pools were available. Regardless of the number of pools, egrets captured the same number of goldfish per pool per day. The time that fish used the exposed habitat was negatively correlated with the time the egret foraged in a pool. However, even in one-pool trials, goldfish emerged from protected habitat occasionally, which sometimes led to their capture.

Keywords: predator–prey behavioural games, optimal foraging, food patches, risk of predation, fear management.

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