Foraging behavior of browsing ruminants in a heterogeneous landscape

Movement patterns of white-tailed deer (Odocoileus virginianus) and Spanish goats (Carpa hircus) were mapped and analyzed to test the hypothesis that foraging movements and behaviors within an Acacia shrub community are significantly related to environmental heterogeneity. Animal response to plant community heterogeneity was characterized using foraging velocity and the animals' foraging path fractal dimension (D_d). Environmental heterogeneity was characterized using the perimeter:area fractal dimension, which represents the shape of shrubs, and the grid count fractal dimension, which represents shrub spatial distribution. The foraging paths of deer were straighter and more directed (D_d = 1.27) than those of goats (D_d = 1.53), and deer responded to the shape of shrub patches, more so than to shrub distribution. The tortuosity of goat foraging paths was apparently affected by distribution of blackbrush (Acacia rigidula) and shrubby bluesage (Salvia ballotiflora). Foraging velocity of deer was affected by the distribution and shape complexity of guajillo (A. berlandieri), which was a major dietary component. In contrast, foraging velocity of goats was affected by the shape complexity of the entire shrub community and by the distribution of ceniza (Leucophylum frutescens), a non-dietary, but prevalent component of the plant community. Results indicate that these two browsing herbivores perceive the same landscape differently.