The Kinetics of Functional Response

Abstract

Holling's Type II functional-response relationship is presented, and the formulations expressing the underlying organismal interactions which might generate such a relation arc generalized into the Type III response typical of predators showing learning behavior. An equation derived through an analogy with allosteric enzyme kinetics is given which will account for both Type II and Type III responses. The response behavior can be explained by three parameters: maximal feeding rate (F); an affinity constant (G) related to handling times, capture efficiencies, etc.; and the number of encounters (n) a predator must have with a prey item before becoming maximally efficient at utilizing the prey item as a resource. A discussion follows on the biological processes which result in shifts from Type II to Type III functional responses. Most of the learning processes involve changes in predator behavior associated with increasing encounters with prey, thus supporting parameter n as a major determinant in shifting thc functional response. Three hypotheses concerning the values parameters F, G, and n will assume under different ecological situations are posited: (l) food preferences will be reflected in an increase in resource-utilization efficiency (F) and affinity (G) and a decrease in values of n encounters; (2) a size ordering of the predators will result in shifts up in the resource-utilization efficiency (F) and affinity (G); while (3) increasing habitat complexity will generate decreases in n and F.