Chapter 5 Population dynamics consequences of fine scale spatial interactions Introduction Functional responses can cause predator-prey models to predict wildly different qualitative behaviours, thus the choice of the functional response form is widely debated. The most frequently discussed in predator-ungulate ecology are the hyperbolic and sigmoidal functional responses, also known as the Type 2 and 3 forms (see Figure 5.1). The Type 2 form (Holling 1965) is solidly based on individual level mechanisms, simultaneously satisfing mass action and maximum physiological rate principles. Multiple-prey systems modelled with Type 2 functional responses predict instability and/or extirpation of one prey type in all but a narrow domain of conditions. Phenomenological forms, such as the ratio-dependent functional response (Arditi and Ginzburg 1989; Akcakaya 1992; Gutierrez 1992) and the Type 3 functional response have been used to stabilize predator prey models. However criticism against using them is that they are not mechanistically based (Abrams 1994; Abrams 1997; Turchin 2002). Nevertheless, the Type 3 has been used in a wolf-ungulate system, and considered to be consistent with empirical trends (Boyce 1992; Boyce and An-
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