When people talk about living near mountain lions, it’s usually about the threat they pose. But what if these big carnivores are also making us safer?
Having more of these big cats in the neighborhood can translate into fewer car collisions with deer, according to research published today in Current Biology.
“Living alongside large carnivores isn’t simply about protecting wildlife; it’s about protecting the many ways they quietly benefit us every day,” said ecologist Mark Elbroch, who was involved in the new study and heads mountain lion research for the conservation group Panthera.
The findings in some ways resemble the more widely known story of how wolves helped revive Yellowstone vegetation by driving down elk populations that had spiraled out of control due to a lack of predators. The actions of one species can ripple through an ecosystem, sometimes in unexpected ways. In the case of mountain lions in Washington state’s Olympic Peninsula, add the unnatural automobile to the equation.
The discovery of this phenomenon emerged from years of work by native tribes of the peninsula to track deer and mountain lion populations. The research involved scientists from the Lower Elwha Klallam, Skokomish, Quinault, Makah and Port Gamble S’Klallam tribes. Wildlife cameras placed at more than 500 locations, combined with GPS-equipped collars on 59 mountain lions, provided a detailed picture of where the cats and their prey were spending time.
The researchers paired this data with the locations of nearly 1,000 collisions between cars and wildlife on the peninsula between 2020 and 2025. Those crashes were associated with more than 80 injuries, two fatalities and $14.7 million in car repairs and medical care.
The pattern of where these collisions happened couldn’t be explained simply by the abundance of deer (based on the wildlife cameras) or by the level of human development and traffic. But when the scientists added the data from the mountain lion collars, it revealed that these cats were a major factor.
In places where mountain lions occurred with relatively high frequency, the likelihood of a car running into a deer was 67% lower, the scientists found. Overall, having lots of mountain lion activity in an area translated into a 76% drop in the total number of expected collisions over five years, according to a model scientists used to analyze the interactions between the cats, their prey and motorists.
The dynamic appears to be related to how deer behave when mountain lions, also known as pumas, are in the area. Much as mountain lions adjust their movements when people are nearby, deer do the same when one of their most fearsome predators is on the prowl.
“Deer alter their use of both space and time where pumas are present, overlapping less with roads and reducing activity at night, when some of the most dangerous collisions occur,” said lead author Justin Suraci, an ecologist at California-based Conservation Science Partners. “Increased road safety thus represents an ecosystem service that large predators like pumas can provide to human communities.”
Wildlife advocates are hoping awareness of benefits like these might help make the case for conserving such species, which often make the headlines only when they attack people.
“Carnivores may well be providing a similar road safety service elsewhere around the globe where populations have persisted and this valuable ecosystem service has just gone unnoticed,” said Suraci.
In fact, deer are far more deadly than mountain lions. A 2011 study by the U.S. Geological Survey found that mountain lion encounters at their 1990s peak resulted in approximately 5 injuries and 1 fatality per year in North America. Two deaths involving mountain lion attacks have been reported in the 2020s.
By contrast, in 2024 alone more than 200 people died in vehicles that ran into wildlife, mostly deer.
Suraci, et. al. “Large carnivores shape road safety through effects on prey space use.” Current Biology. Aug. 5, 2026.
Photo: ©Glen Kalisz, WSDOT
