Interference and the ideal free distribution: models and tests

We review the assumptions and predictions of five competitivedistribution models that predict how optimal foragers will bedistributed across resource patches when gains are reduced byinterference. This review revealed a number of previously ignoredpredictions and assumptions: in particular, there should beno change in relative patch use as competitor density changes.A new model is proposed in which interference results from thecosts of encounters with other foragers and where the gainson a patch are independent of the costs of interference. Thismodel predicts that as density increases, there will be increasedproportional use of lower-quality patches. Past empirical studiesof interference distributions are reanalyzed; none of the studiesprovides strong support for any of the existing ideal free-distributionmodels. We suggest that previous results are more consistentwith the predictions of our new model.