When is habitat assessment an advantage when foraging?

Foragers can often show a broad range of strategies when searching for reso urces. The simplest foraging strategy is to search randomly within a habita t; however, foragers can often assess habitat quality over various spatial scales and use this information to keep themselves in, or direct themselves to, regions of high resource abundance or low predation risk. We investiga ted models that describe a population of consumers competing for a renewabl e resource that is distributed among discrete patches. Our aim was to ident ify what foraging strategy or strategies are expected to persist within a p opulation, where strategies differ in the degree of habitat assessment (i.e . none, local, or global). We were interested in how the optimal strategies are dependent on the cost of assessment and habitat structure (i.e. the va riation in renewal rates and predation risks among patches). The models sho wed that the simple random foraging strategy (i.e. make no habitat assessme nts) often persisted even when the cost of habitat assessment was low. Pers istence could occur when habitat assessment and population dynamics generat ed an ideal free distribution because it could be exploited by the random f oragers. Habitat assessment was more advantageous when consumers could not achieve ideal free distributions, which was more likely as patches became l ess productive. When productivity was low we sometimes observed the situati on where different foraging strategies generated resource heterogeneities t hat promoted their coexistence, and this could occur even when all patches were intrinsically identical. (C) 2001 The Association for the Study of Ani mal Behaviour.