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Why Do Deer Freeze In Headlights?

wild deers crossing highways

There is a popular saying that someone looks “like a deer in headlights.” This idiom describes someone who is overwhelmed or paralyzed by fear or indecision. Many drivers have had encounters with deer on the roads, and often the deer are running across the street when they disrupt the drive. So, do deer actually freeze in the headlights, and if so, why do they do that?

The answer comes down to anatomy and evolution. Deer do indeed freeze in headlights, but not all the time. Here’s why.

car and road divider Do Deer Actually Freeze In Headlights?

Yes. Deer have been known to freeze in the path of an oncoming car. The face of a deer bathed in white luminescence with large eyes staring blankly back at you is an iconic one. It’s also a scene that strikes fear into the hearts of drivers everywhere. This odd occurrence is common enough that the phrase has become widespread and universally known.

Since the phrase is based on a real phenomenon, many people wonder why the deer don’t simply run away. Standing in front of a moving car is not good for anyone’s health. So why do deer freeze in headlights?

deer crossing the road
Image By: Piqsel

Deer Anatomy

The reason why deer stand still when faced with bright headlights comes from the deer’s unique anatomy. Deer are crepuscular. Crepuscular is a fancy science word for animals that are most active in the hour directly before dawn and directly after dusk. (For reference, cats are also crepuscular.) That means that the eyes of a deer have evolved to take in a lot of low light. They see the best when there is very little light, and they see much better in the dark than people do. This is due, in large part, to the fact that a deer’s eyes can dilate to a massive size. The more a pupil can dilate, the more light it can let in.

When a deer turns and looks at your car in the early morning, it gets a face full of extremely bright light. This bright light floods the wide-open pupils of the deer and blinds it. When the deer looks into your headlights, they see nothing but whiteness. The resulting blindness stuns the deer. The animal’s brain cannot make a decision about what to do next, and so it just stands still. Even people are not eager to make a move when they are rendered completely blind.

It would be similar to someone coming into your room at night while you were sleeping and shining a bright spotlight into your eyes. People also feel similar discomfort and confusion when they leave a dark theater and emerge into bright noontime sunshine.

This reaction among deer to car headlights is likely getting more pronounced as time goes on. Headlights continue to get brighter and brighter. The newest luxury headlights feel blinding to people behind the wheel of opposing vehicles, so it is no surprise to think those same headlights will continue to blind helpless deer.

Related Read: Projector Headlights vs. Reflector Headlights: What’s The Difference?

Origins of The Saying “Like a Deer In Headlights”

According to those who study idioms, the saying “like a deer in headlights” first started circulating in the 1980s. The phrase gained steam and popularity when it was used in the 1988 US presidential campaign. After the saying hit the national headlines, people began to use it more regularly in their own speech.

Seeing a deer frozen in the headlights of a car is a relatively recent phenomenon. The modern sealed beam lighting technology found on all cars today wasn’t made standard until 1940. Before that, there was little opportunity to freeze any deer. The lights were just not bright enough. Therefore, it is no surprise that the phrase has only been around for the past forty years.

car and road divider Conclusion

Deer freeze in car headlights because the bright lights blind them. The deer don’t want to freeze, and doing so often leaves them injured or dead. But the brightness of a car’s headlights floods their eyes and overwhelms their brains. Next time you see a deer frozen in bright light, remember that they are likely shocked and terrified. It is not their fault. The deer’s large light-sensitive eyes are how the deer are wired to survive in the wild.

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Featured Image Credit: Mazur Travel, Shutterstock


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