Ecological Determinants of Functional Response

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Abstract
Experimentally derived functional response curves for Peromyscus maniculatus preying upon European pine sawfly cocoons and wheat seeds are analyzed according to a general formula representing both hyperbolic and sigmoidal responses. The response curves were constructed under varying preferabilities of alternate prey and varying degrees of spatial contagion. The important parameter values discussed are the maximum rate of feeding (k); a searing constant (x) equal to the density of resource for which feeding is half maximal; and n, a parameter associated with the amount of "learning" exhibited by the predators. It is shown that when a low palatability alternate food is present the predator will increase both the total utilization (k) and the half—saturation (x) for the test food item being monitored, but will show little change in the degree of learning (n). On the other hand, when foods are changed from randomly dispersed to clumped in the habitat, the predators increase their total resource utilization (k) but decrease their learning (n) and half—saturation (x). The results are discussed in terms of the effect these ecological changes produce in the general behavior of the organism.