Apprehension affecting foraging patterns and landscape use of mule deer in arid environments

Abstract

Foraging animals make trade-offs between food and predation risk. To avoid predation, animals will seek out safe habitats for foraging, often at the sacrifice of food resources. Habitat structure and specific predators prey face determine the risk level of specific habitat types. In northern forested areas, forest edges have been shown to be high risk habitat for mule deer (Odocoileus hemionius) foraging under predation risk from pumas (Puma concolor). In more open habitats, e.g. deserts, a priori knowledge of what characteristics might contribute to predation risk levels for this species complex is lacking. Our objective was to evaluate the potential predation risk faced by mule deer from pumas under different habitat characteristics in the open habitat of the Chihuahuan Desert. We measured apprehension levels in mule deer with Giving Up Densities (GUDs) to evaluate predation risk levels of different habitat variables. We used supplemental (experimental) GUDs and natural GUDs: browse of candelilla (Euphorbia antisiphylitica). Supplemental GUDs were best modeled with macro-habitat variables: they were negatively associated variables, with the interaction between distance to hills and bush height being the strongest predictor, indicating possible predation risk by stalking pumas. Also natural GUDs (candelillas) indicated that mule deer perceived the proximity to hills as riskier. Identification of habitat characteristics that may contribute to predation risk in the Chihuahuan desert will enable further investigation into how habitat characteristics in the Chihuahuan Desert contribute to predator-prey dynamics of mule deer and pumas.