Ecological Scale and Habitat Use

Population density can respond to habitat at different scales. If habitat selection occurs as a consequence of resource exploitation, the density of fine—grained consumers should reflect microhabitat variation. But if habitat use is controlled by a variety of selective pressures, it is no longer apparent whether density should respond to micro— or macrohabitat. These two alternatives can be tested simultaneously by multiple regression models where macrohabitats are represented by dummy variables. When the local densities of two Temperate Zone rodents were analyzed in this way, macrohabitat and temporal effects were consistent significant predictors of rodent density; microhabitat was not. This analysis suggests species whose patterns of resource and habitat use probably depart from classical interpretations of species coexistence. It is probably premature to assess the role of habitat selection in the structure of ecological systems until the results of further tests of habitat scaling are reported.