Washington study finds cougars push deer from roads, cutting crashes by as much as 76%
Cougars may be doing more to protect public safety than many drivers realize.
A new study from Washington's Olympic Peninsula found that in places where the big cats are most active, deer tend to keep farther from roads — and crashes drop dramatically.
Here's what to know
The research, published in Current Biology and highlighted by Mongabay , found that deer-vehicle crashes were expected to be 76% lower over five years in places with cougar activity than in places where the predators were less active.
Overall, the odds of a collision fell by 67%.
The cats appear to change deer behavior rather than simply reduce deer numbers.
Mark Elbroch, director of the puma program at Panthera and a co-author of the study, explained: "The deer know where they're most likely to be at risk of an encounter with a large carnivore, and they avoid these areas more — and they shift their activity to minimize those risks."
Researchers used 503 camera sites, GPS records from 59 collared pumas, and nearly 1,000 reported wildlife-vehicle collisions from July 2020 to June 2025. Deer accounted for 92% of those crashes.
Puma presence was linked to deer being 15% less likely to use road-dense areas and 86% more likely to remain in more isolated habitat.
More background
Deer collisions are a major public safety and economic problem. According to data cited by Mongabay, deer-related crashes in the U.S. total roughly 1.6 million to 2.1 million each year, are associated with 200 to 440 deaths, and create about $10 billion in annual costs.
On the Olympic Peninsula alone, Mongabay reported that wildlife-vehicle collisions from July 2020 to June 2025 led to two human deaths, more than 80 injuries, and an estimated $14.7 million in vehicle-repair and health-related costs.
Cougars themselves are rarely deadly to humans. Glen Kalisz, a habitat connectivity biologist with Washington's transportation agency, told Mongabay that "deer are the more dangerous species."
Just 29 human deaths in the U.S. have been attributed to cougars since 1868, compared with as many as 440 people killed each year in deer-vehicle crashes.
What's being done?
Washington is already trying to reduce wildlife collisions by installing fencing and crossings that funnel animals to underpasses and overpasses rather than onto roads. Kalisz said the new study builds on that work by showing that predator behavior can shape when and where crashes occur. The researchers identified one limitation: the use of developed land as a proxy for traffic volume.
The study suggested next steps, including combining collision reports with carcass-removal data and investigating whether predators may similarly affect other animals involved in roadway crashes.
The findings offer a practical case for coexistence with large carnivores. Beyond supporting healthier ecosystems, cougars may also reduce road hazards, limit costs for families, and even slow the spread of disease by removing weaker prey.
As Elbroch put it, "We know the deer want to be there, and we know the cats are looking for deer."
Where can I learn more?
These articles add context to the cougar findings by looking at the other forces that shape wildlife collisions. From highway design to public funding to habitat pressure, they show how deer behavior and road safety are closely tied.
• In Los Angeles, literally dooming this population helped spur a major wildlife crossing.
• In Montana, lawmakers created dedicated funding to support large wildlife crossings along dangerous highways.
• Across U.S. cities, a major new threat faced by deer is reshaping where herds can persist.
Safer roads depend on habitat, infrastructure, and animal behavior working together.
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