Why do deer just freeze when you’re driving along and you catch them in your headlights? It’s because they’re actually blinded by the lights.
A column in the New York Times explains that since deer are most active at dawn and at dusk, their vision is optimized for low light. When your headlights are on them, they can’t see anything, so they simply freeze.
“They don’t know what to do, so they do nothing,” says biologist David C. Yancy.
The article also notes that while deer are good at detecting motion (like a possible predator), they’re not good at seeing details at a distance. By human standards, they’d be considered legally blind. Deer-car collisions peak at this time of year, the fall breeding season, because males are in pursuit of females, who, in turn, are often running away from them and not looking where they’re going.
Not included in the article is an important tip for what to do, and not do, when you see a deer on the road. Slow down, but try not to swerve. It’s counter-intuitive, and difficult to resist doing, but to a deer you’re just another predator. She understands what to do when someone is trying to catch her. What she doesn’t understand is when someone is trying not to catch her! So a lot of the accidents that take place are the result of the deer and the car both swerving and crashing into each other.