Wildlife corridors don't trap prey, University of Alberta research finds

Wildlife passages, like those in Banff National Park, are meant to help animals cross roads safely, but researchers and ecologists have long been asked about possible unintended consequences of the structures.

Study captured thousands of images of mammals using structures in Quebec

One of the research team's remote photos shows a North American red squirrel carrying nest-building materials through a wildlife underpass in Quebec in the summer of 2014. (Submitted by April Martinig)

Wildlife crossings like those in Banff National Park are meant to help animals cross highways safely, but ecologists have long been asked about possible unintended consequences of the structures.

New research out of the University of Alberta disproves a common theory that predators could exploit the corridors by using them to trap prey.

Researchers tested the prey-trap hypothesis by placing remote cameras in 17 wildlife passages in the Laurentides Wildlife Reserve in Quebec between May of 2012 and August of 2015.

They measured how often some small and medium-sized predators and prey — such as weasels, mice, moles and raccoons — appeared on the passages. A camera at each entrance, when triggered by heat and movement, took a series of photographs.

An aerial view of a wildlife overpass in Banff National Park. (Parks Canada)

The cameras captured more than 11,000 mammals using the wildlife underpasses but did not capture a single predation episode or attempt. 

The researchers also found no photo evidence of any larger predators, like wolves, coyotes or lynx, using the wildlife passages.

Based on the images gathered, predators did not follow prey into the passages and prey tended to avoid the paths after predators had used them. 

"This study is showing that one of our biggest concerns, which was predators catching on to the prey using the passages, isn't actually as much of a problem as we thought it would be," April Martinig said Tuesday in an interview with CBC's Radio Active.

Martinig is a PhD candidate in ecology at the U of A and lead author of "Temporal clustering of prey in wildlife passages provides no evidence of a prey-trap," which was published Monday in the peer-reviewed journal Scientific Reports.

Martinig said she found the results reassuring since she often hears from members of the public who worry wildlife crossings could be putting smaller animals directly in predators' paths.

Scientists will still need to monitor wildlife passages in case predators eventually catch on, she said, but for now, building structures that exclude predators should not be a concern.