ANIMAL MOVEMENT IN HETEROGENEOUS LANDSCAPES - AN EXPERIMENT WITH ELEODES BEETLES IN SHORTGRASS PRAIRIE

1. The role of small-scale vegetation heterogeneity in determining the movement characteristics of darkling beetles was studied in a semi-arid grassland. 2. We tracked the movements of 75 individuals of three Eleodes spp. in small plots representing different vegetation cover types and grazing intensities. Beetle movements were strongly influenced by vegetation structure, with net displacements highest in bare ground and grass cover types and lowest in cactus and shrub. The three beetle species responded differently to grazing intensity. 3. When pathway structure was analysed by its fractal dimension, a measure which incorporates several length scales, beetle species differing in body size had similar pathway structures over a broad range of microlandscape heterogeneity. 4. Simulations using a correlated random walk showed that observed beetle pathways had significantly greater net displacements than theoretical expectations for all treatment groups, but were closer to expected values in cactus and shrub than in bare ground and grass vegetation. 5. The fractal dimensions of observed beetle pathways were also different from simulated pathways, indicating that the similarity in the fractal structure of movement pathways observed in field treatments was not artefactual. Recognition of this size-scaled similarity in animal movement studies may facilitate comparisons of movement properties of animals that respond to the patch structure of the landscape at different spatial scales.