Changing Our Clocks Takes Surprise Toll on Deer

Collisions with cars spike after the November switch, new study finds
By Rob Quinn,  Newser Staff
Posted Nov 3, 2022 6:00 PM CDT
Permanent Daylight Saving Would Save Deer, Human Lives
"If you drive two hours after dark, you’re 14 times more likely to hit a deer than if you drive before dark," Cunningham says.   (Getty Images/Ockra)

Deer don't use clocks but they would still benefit enormously from making daylight saving time permanent, researchers say. According to a study published in the journal Current Biology, the change would prevent the road deaths of more than 36,000 deer annually, along with an average of 33 human deaths and around 2,000 injuries to humans. Researchers analyzed data on more than 1 million deer-vehicle collisions between 1994 and 2021 and found that collisions are 14 times more likely in the two hours after sunset than the two hours before sunrise, meaning deer—and drivers—would be better off with more light in peak evening driving hours. Making daylight saving time permanent would also save around $1.2 billion in traffic costs annually, researchers say.

"We were surprised at the magnitude of the results," says study co-author Laura Prugh. She tells USA Today that researchers thought the later sunrise and earlier sunset would balance out more evenly. Clocks will go back an hour at 2am ET on Sunday. According to the study, collisions go up 16% in the week following the change. "The time switch occurs pretty much exactly smack bang in the middle of the mating period, in particular, for white-tailed deer," says co-author Calum Cunningham, per NBC. During mating season, he says, male deer are more vulnerable to accidents because they "go a little bit crazy—they increase movement and are fixated on reproducing."

"This is one fairly consequential factor for both wildlife and people that hadn’t been considered before, and it turns out it makes a pretty big difference," says Prugh, who hopes lawmakers in Congress will take it into account when they debate the change. The Sunshine Protection Act to make daylight saving time permanent passed the Senate unanimously in March but it has been stalled since then in the House, where lawmakers say it is not a priority. (Read more daylight saving time stories.)

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