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 often 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 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. Acknowledgement 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.