Adam Messer

Climatic variation can change landscape conditions at fine spatial scales over short time periods, thereby influencing species responses to the environment. Snowpack is a component of climatic variation that has recently been modeled in a geographic information system with enough spatial and temporal detail to assess responses of animals to this dynamic landscape component. We examined elk distributional responses to variable snowpack conditions by comparing landscape parameters at observed locations of instrumented elk to randomly selected locations representing the landscape available to instrumented elk. Daily snowpack estimates were obtained for 3126 random elk locations, and their associated random locations, collected over 5 winter seasons. Using log odds ratios, we documented a higher likelihood of elk occurring at locations with low snow mass estimates compared to high snow mass estimates and also determined that likelihoods increased at low snow mass levels as landscape-scale snow severity increased. In addition, the likelihood of elk occurrence increased as snow heterogeneity at a location increased. Akaike Information Criterion model comparison techniques, using conditional logistic regression, revealed that snow heterogeneity had a strong positive coefficient estimate when added to models containing static landscape covariates, greatly increasing the explanatory power of such models. Snow mass estimates were not well supported using this approach, however, suggesting that additional mechanisms influencing elk distribution should be incorporated during future model development. Results from these analyses support known distributional responses of large herbivores to snow, and also reveal additional complexity in those responses associated with landscape-scale snow conditions and local snow pattern. Advancement and application of current climatic modeling techniques will undoubtedly allow further assessment of species responses to variation in climate at increasingly detailed biological, temporal and spatial scales.

Publication:  In preparation

Funding:  National Science Foundation