Authors:

Jackson Doyel, Molly Miller, Clayton BonDurant

Abstract

(Currently conducting analysis)

Highways threaten ecological connectivity and driver safety through wildlife-vehicle collisions and habitat fragmentation. In addition, they may contribute to the anthropogenically-influenced population growth of scavenging bird populations like ravens, increasing pressure on sensitive species including Gunnison sage grouse. Understanding where wildlife crosses, where collisions occur, and how these collisions influence scavenger behavior is crucial for developing effective mitigation strategies. During winter in the Upper Gunnison Basin, large ungulates including elk and mule deer must cross highways that bisect their migratory routes and winter range. Collisions with these animals may provide extended or uncontested food opportunities for ravens over the winter months. To investigate these interconnected impacts, we conducted a three-prong study along five sections of local highways SH 135 and US 50. First, we implemented trail camera surveys at locations with historical wildlife activity to gauge ungulate movement patterns throughout the winter. Second, we conducted weekly roadkill surveys to relate collision risk with ungulate activity levels and other currently collected roadkill data sets from CPW and CDOT. We simultaneously documented the presence and absence of scavenging birds including ravens and magpies on fresh and older carcasses. Third, to isolate the highway effect on scavenger behavior, we monitored 15 pairs of roadkill (14 deer, 1 elk) under 24-hour trail camera surveillance, with one carcass placed within 15.5 meters of the highway and its pair placed between 104 and 835 meters away from the road under similar habitat conditions. This paired design allows us to determine how quickly carcasses are consumed and by what species when placed either near or away from roadways. With raven populations growing across the United States and highways increasingly interrupting historical ungulate migration corridors, our integrated approach examines how roadways impact scavenger populations and helps identify priority locations for future wildlife-vehicle collision mitigation strategies.