A puma crossing a road on the Olympic Peninsula in Washington state. Nicolás Lagos / Panthera

Mountain lions in Washington state may be cutting down on traffic accidents by scaring deer away from roads, new research finds.

Deer often avoid open spaces, including roads, when predators are nearby. But while it has long been suggested that predators might tamp down on traffic collisions with prey, that has never been demonstrated in areas where big predators are well established, researchers say.

The new study tracked wildlife across the Olympic Peninsula in Washington state, comparing collision data with photos from camera traps that revealed the whereabouts of mountain lions. The big cats, sometimes referred to as cougars or pumas, prey primarily on deer.

Researchers found that where mountain lions were active, deer avoided roads. Overall, deer in those areas were 15 percent less likely to be found near roads, which led to a 67 percent drop in the odds of a traffic accident involving deer.…