The prevalence of intraguild predation in productive environments has long been puzzling ecologists. Adaptive foraging by the intraguild predator is one of the probable hypotheses that explain the coexistence of the intraguild prey and predator in productive environments. Krivan and Diehl (2005) considered a model of intraguild predation, assuming an adaptive foraging rule in which the intraguild predator feeds on the less profitable resource only if the more profitable one is rare. Although the adaptive omnivory enlarged the persistence region of the intraguild predator, it could not facilitate persistence of the intraguild prey.

In this talk, I investigate a similar model to that examined by Krivan and Diehl. However, instead of assuming adaptive diet shift by including or excluding the less profitable prey or resource into the menu, I compare the dynamics of models with different profitabilities of the intraguild prey and resource to the intraguild predator. I will show that exclusion of the intraguild prey can never occur even in highly productive environments if it is the more profitable to the intraguild predator and that extinction of the intraguild predator may result if it feeds on a great amount of the less profitable resource.