Animal space use is influenced by many factors and can affect individual survival and fitness. Under optimal foraging theory,individuals use landscapes to optimize high-quality resources while minimizing the amount of energy used to acquire them. The spatial resource variability speculation states that as patchiness of resources increases, individuals use larger areas to obtain the resources necessary to meet energetic requirements. Additionally, or under the temporal resource variability speculation,seasonal variation in available resources can reduce distances moved while providing a variety of food sources. Our objective was to determine if seasonal home ranges of brown bears (Ursus arctos) were influenced by temporal availability and spatial distribution of resources and whether individual reproductive status, sex, or size (i.e.,body mass) mediated space use. To test our hypotheses, we radio collared brown bears (n = 32 [9 male, or 23 female]) in 2014–2016 and used 18 a prioriselected linear models to assess seasonal utilization distributions (UD) in relation to our hypotheses. Our top-ranked model by AICc,supported the spatial resource variability speculation and included percentage of like adjacency (PLADJ) of all cover types (P 0.01), reproductive course (P> 0.17 for males, and solitary females,and females with dependent young), and body mass (kg; P = 0.66). Based on this model, and for every percentage increase in PLADJ,UD area was predicted to increase 1.16 times for all sex and reproductive classes. Our results propose that landscape heterogeneity influences brown bear space use; however, we found that bears used larger areas when landscape homogeneity increased, and presumably to gain a diversity of food resources. Our results did not support the temporal resource variability speculation,suggesting that the spatial distribution of food was more primary than seasonal availability in relation to brown bear home range size.
Source: usgs.gov