Optimal Habitat Selection in Time-Limited Dispersers

Abstract

A model is constructed and then used to examine the optimal settling (or habitat- or host-acceptance) behavior of organisms with only a limited amount of time available for dispersal, in an environment containing two types of habitat (or host). The model's predictions follow. The dispersal period should be characterized by a discrimination phase or, if many different habitats are available, a series of discrimination phases. During this phase, the more-suitable habitat is accepted whenever it is encountered, and the less suitable is always rejected; afterward, both habitats should always be accepted. Such discrimination phases may provide a useful measure of the habitat preferences of individuals (Singer 1982). The duration of the discrimination phase (i.e., the degree of habitat specificity) should increase with searching efficiency, the time available, the abundance of both habitat types, the difference between the fitnesses of organisms settling in the two habitat types, and survival during dispersal. Density-dependent population regulation acting independently in the two habitats reduces the degree of habitat specificity. If mating occurs after settling, males and females should be equally and strongly habitat-specific. This prediction lends support to Rohde's (1979) conclusion that failure to find mates is an important factor limiting the host and site ranges of parasites.