Using the functional response to determine the nature of unequal interference among foragers.

The food intake rate of foragers may be reduced as a result of interference, which may be asymmetric among individuals and occur as a result of intimidation, direct aggression or filtering. It is important to distinguish among these types of interference, because each can have different consequences for individuals, foraging groups and populations. We demonstrate the application of the functional response as a tool for distinguishing between types of interference. We apply the approach to juvenile Atlantic salmon and show that stepwise elimination of interference types is possible from regression analyses of functional responses, identifying filtering as the only effective type of interference in the study environment.