Sexual size dimorphism mediates effects of spatial resource variability on A merican black bear space use

The distribution of animals is influenced by numerous factors including spatial distribution and temporal availability of resources. We tested the spatial resource variability hypothesis (increasing landscape heterogeneity results in increasing amount of space use) and the temporal resource variability hypothesis (temporal variation in resources reduces amount of space use) using location data from radiomarkedAmerican black bearsUrsus americanusinMissouri andArkansas,USA. We used 95% utilization distributions (UDs) to define individual seasonal space use and constructed 22 models using covariates that described composition, spatial arrangement and diversity of land cover types (an index of heterogeneity or patchiness); seasonal hard mast production; and seasonal use of land cover to test our hypotheses using linear modeling and small‐sample Akaike information criterion (AICc) model selection approaches. TheAICcbest performing model supported the spatial resource variability hypothesis and included Shannon diversity index [95% confidence limit (CL) of coefficient = 1.56–2.42] and sex (male; 95%CLof coefficient = 0.05–0.49) as covariates that explained variation in transformed values ofUDsize. Predicted and observed values during model evaluation were highly correlated (r = 0.90). As land cover heterogeneity increased,UDsize increased, likely a consequence of bears responding to greater patchiness to maintain sufficient resources. Further, theShannon diversity index was greater for males than females , suggesting larger bodied males used larger areas to meet their higher energetic costs due to landscape fragmentation. Studies of resource hypotheses in solitary species should consider intraspecific allometric relationships such as sexual size dimorphism as has been addressed using group size in social species.