Consumer functional responses under intra- and inter-specific interference competition

Mechanistic models of population, community and ecosystem dynamics require the mathematical description of trophic interactions in the form of functional response equations. There is a wealth of such equations developed to incorporate the effects of multitude forms of foraging behaviour including intra-specific interference competition. However, there has been no attempt to include inter-specific behaviours beyond the obvious consumer-resource relationship, and thus, mechanistic models of communities and ecosystems remain limited in their incorporation of individual behaviour. In this paper we extend existing functional response models to account for both intra- and inter-specific interference behaviours. Together with response surface experiments, these can be used to investigate the role of both types of interference for a given species' resource acquisition efficiency. We illustrate this with data from foraging trials of guppies Poecilia reticulata in the presence and absence of a competitor species, Hart's killifish Rivulus hartii. Our results show that in the studied example, intra-specific interference is important and stronger than inter-specific competition.