Cougars cut deadly vehicle-deer collisions in the U.S. by up to 76%, study shows

A study in Current Biology found that cougars on Washington's Olympic Peninsula reduce deer-vehicle collisions by up to 76% simply by making deer avoid roads and shift activity to daylight. Researchers from Panthera and Conservation Science Partners combined 503 camera locations, GPS data from 59 collared pumas, and nearly 1,000 reported wildlife-vehicle collisions from 2020-2025 to reach the finding.

Deer accounted for 92% of collisions, and where pumas were present, deer were 15% less likely to occupy high-road-density areas and 86% more likely to stay in remote terrain. The effect comes from deer altering behavior across an entire herd, not from cougars simply eating enough deer to shrink the population — a single cougar eats about 48 deer a year, far too few to matter numerically.

Nationally, deer-vehicle collisions kill 200-440 people annually and cost about $10 billion; on the Olympic Peninsula alone the study period saw two deaths, over 80 injuries, and $14.7 million in estimated costs. Washington's transportation agency notes the research fits a broader pattern where wildlife behavior, not just wildlife numbers, drives road safety outcomes.

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