Wildlife crossings, which many wildlife managements promote as a way to allow animals to bypass busy roads, may have an issue: Fear. According to new research published in Plos One, some big game animals are too scared to use wildlife crossings.

The study zone was the Trans-Canada Highway in Banff National Park, where a wildlife underpass is built on a four-lane highway. Researchers installed two motion-activated video cameras at the crossing to record the number of vehicles passing in 15-second intervals, while also recording the types of vehicles. They compared those stats to the behavior of elk and white-tailed deer in the area. If an animal was eating near the tunnel when a vehicle approached, did it continue to feed or did it change its behavior?

“It’s only through studies like this that focus on how animals perceive and react to the stimuli in their environment, which can attract or repel them, that we’ll gain the necessary insights to develop effective wildlife crossings,” Daniel Blumstein, UCLA professor of ecology and evolutionary biology told Science Daily. “Different species are likely to respond differently and other external contextual cues might also influence how a given species responds.”  

The collection of nearly 600 separate wildlife videos over six months shows vehicles, even with a dedicated wildlife crossing nearby, change an animal’s behavior. Both deer and elk reduced forage time when a vehicle was nearby. They were more skittish when vehicles passed by intermittently than when there was steady traffic.

“We are not certain why animals are more responsive to fewer vehicles,” said Eric Abelson, who was a postdoctoral fellow at UCLA’s La Kretz Center for Conservation Science during the study. “It is possible that when there are many cars barreling down the road, they can be heard from farther away and don’t surprise the animals as much.”

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In the study, deer were often observed to stop eating and start running away from the road. Elk typically stopped eating and started looking around but didn’t necessarily flee. But in both cases, they avoided using wildlife crossings because of fear of traffic. The researchers hope these findings could be used to help improve the location and efficiency of wildlife crossings, potentially by using sound and light barriers so animals feel safer.