Mountain lions tied to 76% fewer deer crashes, study says

Mountain lions are linked to far fewer deer-vehicle crashes in parts of Washington state's Olympic Peninsula, with collisions falling by as much as 76 percent in areas the predators frequent, according to a study published Wednesday in Current Biology.

Lead author Justin Suraci, of Conservation Science Partners, said the effect was not because mountain lions were eating enough deer to reduce herds. He said fear of the predators appeared to make deer avoid roads and developed areas and reduce nighttime activity.

The researchers used data from 503 camera traps and 59 collared mountain lions collected through a long-term Panthera study with several Native American tribes and nations. They found that where mountain lions were present, deer were more active by day than by night, 15 percent less likely to be in areas with a high density of roads and 86 percent more likely to occupy remote habitat far from developed areas.

The team divided the peninsula into five-by-five-kilometre cells and overlaid crash data. It found up to a 76 percent reduction in deer-vehicle collisions in areas with high mountain lion presence over a five-year span.

State data for 2020 to 2025 showed two human deaths, more than 80 injuries and $14.7 million in estimated health expenses and vehicle repairs from crashes with ungulates on the peninsula.

Suraci said researchers could not yet estimate how many deaths, injuries or costs mountain lions had prevented, but said the toll would be substantially higher if the pumas were absent. Panthera puma programme director Mark Elbroch said the findings could help people live alongside cougars.