Unequal competitor ideal free distribution in fish? Evol

Key predictions of unequal competitor ideal free distribution models were tested using a continuous input situation. Ten individually identifiable cichlid fish competed for food items at either end of their tank. Their distribution fitted the predictions of the equal competitor, continuous input ideal free model almost perfectly. However, examination of individual intakes revealed significant variation in individual success and relative competitive ability between patches. Contrary to expectations, fish did not exclusively use the patch where their intake was higher, although individuals experiencing greater dierences in intake rate between patches were more selective. We found no evidence for a truncated distribution or even a correlation between com-petitive ability and patch quality. Changing the input regime to reduce competition did not produce a decrease in the range of intake rates between individuals. This study indicates the value of future empirical and theoretical work on how relative competitive ability varies with the nature of the foraging environment