Intrinsic and Extrinsic Factors Simultaneously Modulated the Use of Roadways by Golden Eagles During Winter

Animals often face trade-offs wherein foraging opportunities may coincide spatiotemporally with higher risk of mortality, especially within landscapes altered by humans. Resolving such trade-offs can depend on intrinsic factors such as age and sex, and extrinsic factors (e.g., resource availability) within the surrounding environment. Yet both are rarely assessed simultaneously. Roads constitute a widespread form of human-induced habitat alteration that concurrently offer potential food rewards, in the form of carrion from roadkill, and risk in the form of death by vehicle collision. We evaluated the extent to which suites of intrinsic and extrinsic factors modulated the selection for areas near roads by a large opportunistic scavenger, the golden eagle (Aquila chrysaetos). We used a collaborative, multi-agency telemetry dataset of 51 golden eagles overwintering in Wyoming, USA during 2014 to 2023 representing 175 unique eagle-years. Both intrinsic and extrinsic factors influenced road use. Males were 14.2 times more likely than females to select areas closer to roads. Adults, compared with their subadult counterparts (Subadult I, Subadult II, and Subadult III) were 16.3, 16, and 15.3 times more likely to select areas near roads, respectively. Moreover, individuals were more likely to select areas near roads during periods with higher snow depth on the landscape. Specifically, during periods of high snow depth (> 17.9 cm) golden eagles were 17 times more likely to select areas near roads than during periods with no snow. Our results suggest that both intrinsic and extrinsic factors influenced proximate habitat decisions and the use of areas near risky landscape elements. Our work has important implications for the contexts under which efforts to reduce golden eagle mortality, such as the removal of carcasses from roads, would be most effective.