Effects of spatial grouping on the functional response of predators

A unified mechanistic approach is given for the derivation of various forms of functional response in predator-prey models.. The derivation is based o n the principle of mass action but with the crucial refinement that the nat ure of the spatial distribution of predators and/or opportunities for preda tion are taken into account in an implicit way. If the predators are assume d to have a homogeneous spatial distribution, then the derived functional r esponse is prey-dependent. If the predators are assumed to form a dense col ony or school in a single (possibly moving) location, or if the region wher e predators can encounter prey is assumed to be of limited size, then the f unctional response depends on both predator and prey densities in a manner that reflects feeding interference between predators. Depending on the spec ific assumptions, the resulting functional response may be of Beddington-De Angelis type, of Hassell-Varley type, or ratio-dependent. (C) 1999 Academic Press.