Origin of the Type III Functional Response

In this chapter I review the many ways that functional responses may show a sigmoidal shape rather than the simpler asymptotic shape. I break down the potential for prey dependence of the space clearance rate through effects on each of the component mechanisms. Given the emergent nature of the functional response, type III curves can arise through density dependence of the probability of successful capture, prey detectability, and predator–prey encounter rates. Given the variety of mechanisms, it may be possible that there are really multiple types of type III curve. I also raise some concerns with the standard type III model and offer an alternative model that gets around these problems.