Competitors and Habitat Use

Abstract

The effects of a species'' and its competitor''s density on the choice of habitats exploited by the species were examined in models where there is a cost of selecting only 1 habitat. The state space of the 2 species densities is partitioned into regions where the species take either their preferred habitat (assumed to be different), or both habitats. The functions partitioning the regions are called isolegs. Also superimposed upon the state space are the familiar isoclines, whose intersection gives the equilibrium densities for both species. The slopes of the isoclines are different in the different regions of the state space. Isoclines and isolegs are functionally dependent. Conditions can be derived under which both species coexist using mutually exclusive habitats, and where, as a consequence, the isoclines intersect perpendicularly. These conditions appear to be easy to obtain ecologically, and are likely to be encountered when each species inhibits its competitor strongly in its (the species'') preferred habitat.