Type III functional response is similar to type II in that at high levels of prey density, saturation occurs. But now, at low prey density levels, the graphical relationship of number of prey consumed and the density of the prey population is a more than linearly increasing function of prey consumed by predators. This accelerating function is largely descriptive, and often justified by learning time, prey switching, or a combination of both phenomena, but the type III functional response lacks the rigorous theoretical underpinning of the type II functional response.