Golden eagle use of winter roadkill and response to vehicles in the western United States

Vehicle collisions are a significant source of wildlife mortality worldwide, but less attention has been given to secondary mortality of roadkill scavengers, such as the golden eagle (Aquila chrysaetos). We sought to quantify golden eagle winter use of roadkill mammal carcasses and eagle flushing from vehicles in Oregon, Utah, and Wyoming, USA, as proxies for strike risk, using motion-sensitive cameras. We monitored 160 carcasses and captured 2,146 eagle-vehicle interactions at 58 carcasses (1-240 observations/carcass) during winters of 2016-2017, 2017-2018, and 2018-2019. We used generalized linear mixed models, which suggested that eagle use of carcasses declined with time since camera deployment but increased with distance to road. Flushing from vehicles decreased with carcass distance to road but was higher in the morning, in response to larger vehicles and vehicles in the closest lane, and in the Oregon study area. We suggest that roadkill distance to road is the easiest factor to manipulate with the dual benefits of increasing food availability to golden eagles and decreasing flush-related vehicle strike risk. We recommend that roadkill be moved at least 12 m from the road to increase eagle use and decrease flushing 4-fold relative to behavior observed at the road edge. Because flushing from roadkill is believed to be the primary cause of eagle-vehicle strikes, informed roadkill management has the potential to reduce human-caused mortality of golden eagles.

Automated summary

Vehicle collisions are a major cause of wildlife mortality, and this study focuses on the secondary mortality of roadkill scavengers, specifically golden eagles. By monitoring golden eagle behavior and interactions with roadkill carcasses, the study provides insights into the factors influencing eagle use and flushing from vehicles. The findings suggest that managing roadkill distance to roads can both increase food availability for golden eagles and decrease the risk of eagle-vehicle strikes.