When the mean is meaningless: Drivers of spatial behavior in a generalist carnivore

Despite the ecological expression and conservation importance of diverse behavioral tactics in animals, there is often friction associated with conventional analytical approaches and inference concerning variation in spatial behavior. Implicitly or explicitly, population-level inferences are generally the main objective of studies, but interpretations can be ambiguous in the presence of divergent behavioral tactics across individuals or cohorts, as with generalist species. We pursued a novel analytical approach and assessed the underlying mechanisms driving variation in spatial behaviors of generalist species using the American black bear (Ursus americanus) as our focal species. We quantified individual variation in habitat selection expressed by black bears using individual models for 35 collared bears across four study areas in Wyoming, USA. We modeled how state-dependent factors (age, sex, δ¹⁵Nitrogen, and body fat) and resource availability influenced behavioral variation in resource selection. We observed vast variation among individuals, demonstrating patterns consistent with a generalist species. Black bear resource selection differed with changes in state dependence and resource availability. Specifically, traits uniquely important to black bear success, body fat and carnivory, explained variation in selection for forage indexed by normalized difference vegetation index (NDVI), forests, and riparian areas. Environmental heterogeneity via differences in resource availability magnified behavioral variation in resource selection by black bears. Selection trends for NDVI and deciduous shrubs were explained by resource availability, indicating black bears exhibited functional responses in habitat selection. These insights emerged from our analytical approach; had we implemented a more conventional, population-level assessment, we would have simply concluded that black bears displayed behavioral neutrality with respect to forage resources. Acknowledgment of behavioral variation when considering spatial behavior of generalist species provides a more representative understanding of individuals within a population, and our analytical approach offers a solution to uncovering drivers of individual variation in spatial behavior.