A simple generalized model of attack by predators and parasites

A generalized descriptive equation for the effect of prey density on the instantaneous rate of attack was proposed; urn:x-wiley:09123814:ere0141:equation:ere0141-math-0001 where A ( N o ) is the number of attacks per predator during time T t , N o is the prey density, T t is the total time the prey was exposed, T h is the handling time per prey, a ′ is the rate of successful search, and c is the facilitation coefficient. The proposed equation can describe all types of the functional response curves; with c=a′ t h (pseudo Type I), with c =0 (Type II), with c>a′ t h (Type III), and with c <0 (Type IV). The applicability of the equation was tested against the results of a simulation model and available laboratory and field data on predation. The equation described these data very well and in many cases yielded biologically interesting insights, although the equation was proposed primarily for descriptive purposes.