FACTORS INFLUENCING THE FREQUENCY OF ROAD-KILLED WILDLIFE IN YELLOWSTONE NATIONAL PARK

During the 8 year (1989-1996) study period, 939 large mammals were killed by vehicles on roads within Yellowstone National Park (YNP). Elk and mule deer were the species most often killed by vehicles on park roads. Other species killed on park roads include bison, moose, coyote, antelope, beaver, whitetail deer, bighorn sheep, black bear, bobcat, grizzly bear, raccoon, and wolf. Vehicle-wildlife collisions pose a safety threat to people as well as wildlife. Park visitors have been injured and killed in vehicle collisions with wildlife. The authors analyzed the frequency of roadkills in relation to adjacent roadside cover types, posted speed limits, and actual average speed of vehicles. They also estimated the proportion of the park's large mammal population killed by vehicles each year. They concluded that speed of vehicles was the primary factor contributing to vehicle-wildlife collisions. Road design appeared to influence vehicle speed more than the posted speed limit. Cover types and wildlife population numbers also influenced the frequency of vehicle wildlife collisions. Most wildlife species were killed significantly more often in non-forested cover types than in forested types. Wildlife species with the highest population numbers were also the species most often killed by vehicles. Overall, vehicle-caused wildlife mortality does not appear to have a significant negative impact on large mammal populations in the park. However, road-killed wildlife carcasses appear to be a significant source of nutrition for some individual carnivores and scavengers whose home ranges encompass wildlife carcass disposal sites.