Deer see best in dim light, but can't perceive how fast cars are moving -- contributing to an increased number of crashes at night

If you've driven in the fall in Wisconsin, chances are you've either hit a deer suddenly emerging onto the road — or been in a close call.

Deer are “crepuscular” prey animals with eyes that work best in dim light. It’s why drivers are most likely to encounter them on roadsides at dawn and dusk. The majority of Wisconsin deer-related car crashes in 2022 took place between 5 and 6 a.m. and between 5 and 9 p.m.

During the day, deer bed down in sheltered, woody areas to rest and digest. Eating quickly, then retreating to safety for digestion is a predator escape mechanism.

More: Understanding deer behaviors could help prevent collisions with cars in Wisconsin

Jennifer Smith is a behavioral ecologist at UW-Eau Claire. She said it’s useful to understand the deer’s “umwelt,” the unique ways an organism perceives the world.

For example, Smith said, loud noises could be used to scare naturally skittish deer away from high-traffic areas or warn them as a car approaches.

When a car does approach, they are not conditioned or adapted to look both ways before crossing the road. Chris Young, who studies conservation and biology at the University of Wisconsin-Milwaukee, said deer are unable to discern the sound of one approaching car from the general roar of the freeway.

Deer also lack the ability to perceive how quickly a car is moving, according to Scott Hygnstrom, deer ecology researcher and professor at UW-Stevens Point, who has been in 11 deer vehicle collisions.

While deer might see or hear a car coming, they might not register it as a risk, he added.

Contributing to the risk:

The middle of a forest has far less food for deer than an “edge.” It's on borders between landscapes where their favorite foods grow: berries; grasses; “browse,” or the tips of woody shrubs and trees; wildflowers or “forbs,” such as goldenrod, fireweed and lupine.

The edges of roads have the kinds of food deer are attracted to. Add the fact that deer are more active during times of dim light, and that they can't discern how fast a car is approaching, and it's a recipe for a crash.

Cleo Krejci covers K-12 education and workforce development as a Report For America corps member based at the Milwaukee Journal Sentinel. Contact her at CKrejci@gannett.com or follow her on Twitter @_CleoKrejci . For more information about Report for America, visit jsonline.com/rfa .

This article originally appeared on Milwaukee Journal Sentinel: Deer see best in dim light, but can't perceive how fast cars are moving -- contributing to an increased number of crashes at night