A black-tailed deer eyes a busy road in western Washington, contemplating when to cross. © Joe Pontecorvo
A new study co-authored by Conservation Science Partners and Panthera, published in Current Biology, reveals that the presence of pumas (also known as cougars or mountain lions) can reduce deer-vehicle collisions by as much as 76%. In the United States, these collisions account for more than 1.5-million accidents annually, resulting in roughly 200 human fatalities and over $10 billion in economic damages. The research highlights that pumas provide a vital ecosystem service that directly enhances human safety and reduces the financial strain on state road budgets.
The study attributes this reduction to a phenomenon known as the “landscape of fear.” Rather than simply reducing deer populations through predation, pumas fundamentally alter deer behavior. Deer in puma territories become significantly more cautious, specifically avoiding the forest edges near roads where pumas prefer to hunt. The data shows that deer were 86% more likely to remain in remote habitats away from traffic and shifted their activity to daylight hours when pumas are less active, further reducing the likelihood of nighttime collisions.
“We found that large carnivores can make roadways safer through their effects on prey behavior and space use,” says lead author Justin Suraci of Conservation Science Partners. “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,” says Suraci. “Increased road safety thus represents an ecosystem service that large predators like pumas can provide to human communities. And indeed predators likely are providing these and other services in many places where humans and large carnivores coexist, even if these benefits have largely gone unmeasured.”
Conducted on Washington’s Olympic Peninsula, the research utilized five years of crash records alongside data from 503 camera traps and GPS collars on 59 pumas. This is the first study to provide empirical field data linking stable carnivore populations to specific prey behavioral shifts that result in fewer roadway accidents.
The full article is here:
Current Biology, Suraci et al., “Large carnivores shape road safety through effects on prey space use” https://www.cell.com/current-biology/fulltext/S0960-9822(26)00818-3