ASSESSMENT OF PATCH PROFITABILITY AND IDEAL FREE DISTRIBUTION - THE SIGNIFICANCE OF SAMPLING

When allowed access to two food patches differing in food availability, groups of six adult, female, threespined sticklebacks (Gasterosteus aculeatus, L.) distributed themselves between patches according to the ratio of patch profitability, as predicted by the ideal free distribution (IFD) model. However, when individual fish were subsequently prevented from physically sampling patches differing in both food availability and the number of conspecifics present, patch choice did not conform to IFD. Instead, individuals preferred the patch with the greatest number of conspecifics present, regardless of potential foraging rewards. Preference for patches with the greatest number of conspecifics was, however, only evident when conspecifics were feeding. An outline of the decision process used by sticklebacks when selecting among food patches is presented.