How does habitat patch size affect animal movement? An experiment with darkling beetles

We used an experimental model system consisting of darkling beetles (Coleop tera: Tenebrionidae, Eleodes obsoleta Say) in a microlandscape to assess th e effects of habitat patch size on the movement patterns of animals. The ra tio of habitat area to nonhabitat in a 25-m(2) "microlandscape" was held co nstant while the grain of patchiness (patch size) was varied in four treatm ents. Beetle movement pathways were electronically surveyed, and seven path way metrics were used to quantify movement characteristics. ANOVA and Fishe r's Protected Least Significant Difference post hoc comparisons revealed th at both the presence and the grain of spatial heterogeneity influenced how animals moved through landscapes. Intermediate patch sizes elicited the str ongest behavioral responses, whereas movements were similar between finely patchy landscapes with small habitat patches and coarsely patchy landscapes with larger habitat patches. These results indicate that organisms may use landscapes that possess different configurations of habitat in similar way s. Predicting how organisms respond to spatial heterogeneity therefore requ ires an assessment of how organisms use landscapes, in addition to an asses sment of the structural characteristics of landscapes, such as grain size.