THE INFORMATION OF FOOD DISTRIBUTION REALIZES AN IDEAL FREE DISTRIBUTION - SUPPORT OF PERCEPTUAL LIMITATION

Previous tests of ideal free distribution (IFD) under continuous input conditions have demonstrated that more profitable patches tend to be relatively underused compared to that predicted by the theory. We test ed the hypothesis that competitors' perceptual constraints of resource distribution cause this deviation from the IFD. A laboratory experime nt was conducted to determine whether additional information on food d istribution by a light cue that indicates the food input point improve s the IFD theory's fit to the distribution of clone red-spotted masu s almons (Salmonids), Oncorhynchus masou ishikawai, that had been condit ioned to the light as a cue indicating the site with a higher input ra te. In the treatments without a light cue, the distribution of fish wa s closer to a random pattern than an IFD. In contrast, in the treatmen ts with light cue, the distribution of fish was closer to the expected value of an IFD rather than to a random pattern, supporting the perce ption-limit hypothesis. The distribution and the pattern of resource u se by fish in the treatments without the light cue were best explained by the perception-limit model. Our results suggest that it is percept ual constraints that cause deviation from the IFD.