A new study in Wisconsin suggests the predators keep prey away from roads, reducing crashes by 24 percent
May 26, 2021
Research published this week in the Proceedings of the National Academy of Sciences highlights an underappreciated benefit of wild wolf populations: the large predators frighten deer away from dangerous roadways, saving money and lives in the process.
According to the analysis 22 years of data, a county’s deer-vehicle collisions fall by about 24 percent after wolves take up residence there, Christina Larson reports for the Associated Press. Nearly 20,000 Wisconsin residents collide with deer each year, which leads to about 477 injuries and eight deaths annually. There are 29 counties in Wisconsin that have wolves.
“Some lives are saved, some injuries are prevented, and a huge amount of damage and time are saved by having wolves present,” says Wesleyan University natural resource economist Jennifer Raynor to Ed Yong at the Atlantic.
The study estimates that wolves save Wisconsin about $10.9 million in losses each year in prevented car crashes, which is far greater than the compensation paid by the state to people who lose pets or livestock to wolves.
“Most economic studies of wolves have been negative, focusing on livestock losses,” says wolf expert Dave Mech, who works at the U.S. Geological Survey in Minnesota and was not involved in the study, to the AP. “But wolves also reshape ecosystems in many ways, although that’s hard to measure economically.”
Most of the reduction in collisions was due to the “landscape of fear” that wolves create. Wolves tend to follow clear paths through the landscape, like streams. In an area that has been developed by humans, wolves follow roads, trails and pipelines. Deer adapt to the wolves’ presence by staying away, which would reduce the chance that they would get hit by a car.
“The icing on the cake is that wolves do this work all year long at their own expense,” says Western University ecologist Liana Zanette, who was not involved in the study, to the Atlantic. “It all seems like a win-win for those wolf counties.”
Wolves killing deer only accounted for about six percent of the drop in deer-vehicle collisions, reports Jack J. Lee for Science News. The drop in collisions didn’t just happen because wolves kill deer, so culling deerduring hunting season wouldn’t necessarily limit car collisions to the same extent as having wolves present.
The deer that the wolves do manage to kill would likely be the least risk-averse, and most likely to run in front of cars. But a detailed understanding of wolf and deer behavior would come from research that tracks the animals with collars, which was not a part of the new study, says University of Wyoming ecologist Matthew Kauffman to the Atlantic.
The research stands out from other studies of wolves’ impact on the environment because it highlights a benefit that wolves bring to the humans that live nearby. The regions that support wolf reintroduction tend to be urban, while rural communities generally oppose it. That was the case in Colorado, where wolf reintroduction narrowly passed in a vote in November. In sharp contrast, the Idaho state government recently passed a law to kill 90 percent of its wolves.
“The most interesting thing to me about choosing Wisconsin as a case study is that this is a human-dominated landscape,” says Raynor to Science News.
The estimated savings to Wisconsin are about 63 times higher than the cost of compensating people for losses caused by wolves. Raynor adds to Science News there are economic factors that weren’t taken into account in the new study, like the cost by deer to agriculture and through Lyme disease.
Adrian Treves, a conservation biologist at the University of Wisconsin, tells the AP that the study “adds to growing awareness that scientists should consider both the costs and the benefits of having large carnivores on the landscape.”