Mountain lions cut deer crashes by 76 percent

Where mountain lions roam the Olympic Peninsula, drivers crash into far fewer deer, according to a study published August 5 in Current Biology. Researchers found that the presence of pumas corresponded with a 76 percent decline in deer-vehicle collisions over five years in western Washington. The reason is behavioral. When cougars are around, deer head deeper into the woods and avoid roadsides, the exact edge habitats where ambush predators like to hide. Deer also shift to daytime activity, away from the darker hours when the worst crashes happen. The team worked with five Native American communities that shared data from 503 camera trap sites and 59 collared pumas. Deer alone caused 92 percent of the 953 crashes mapped, which killed two people and cost an estimated $14.7 million. Liana Zanette, an ecologist at Western University who was not involved, put it plainly to New Scientist. "Cougars also provide this service completely free of charge."