Deer In Headlights: Why Do They Stand There?

(ANIMAL FACTS/SCIENCE) We’ve all heard the expression “like a deer in the headlights,” but why do deer just stand in front of a moving car? Here’s why headlights can make a deer freeze. Also, see the linked article below for tips to avoid hitting deer. — Global Animal

Deer In The Headlights

The New York Times, C. Claiborne Ray

Q. Why do deer get transfixed by car headlights and just stand there in harm’s way?

A. “Deer are crepuscular,” said David C. Yancy, a deer biologist with the Kentucky Department of Fish and Wildlife Resources. Their activity peaks within an hour or so on either side of sunrise and sunset, so their vision is optimized for very low light.

When a headlight beam strikes eyes that are fully dilated to capture as much light as possible, deer cannot see at all, and they freeze until the eyes can adjust.

“They don’t know what to do, so they do nothing,” Mr. Yancy suggested.

Continuing research at the University of Georgia on whitetail deer vision suggests that by human standards, deer are legally blind. A researcher interviewed in the September/October issue of Arkansas Wildlife estimated their vision at 20/200: where a person with normal eyesight can discern an object’s details at 200 yards, deer need to be within just 20 yards away. (They are better adapted to detecting motion.)

Deer-car collisions peak with the fall breeding season, with males moving around to find receptive females — and unreceptive females in retreat — and no one has figured out a good way to prevent them, Mr. Yancy said. For now, he added, the combination of “deer crossing” signs, articles to warn the public, and defensive driving will have to do.

More New York Times:

Related Story: Deer Crossing: Avoid Roadkill Disaster