Study Proves Wildlife Crossing Structures Maintain Gene Flow in Bear Population

A new study claims that the wildlife crossing structure along the Trans-Canada Highway helps maintain gene flow among healthy populations of grizzly and black bears.

According to the scientists at the Montana State University, the wildlife crossing structure along the Trans-Canada Highway promotes gene flow among healthy population of bears. This new genetics study is based on the analysis of 10,000 hair samples collected from black bears and grizzlies, during a three-year study period.

"Showing that the black bears and grizzlies using the crossings to traverse the highway are also breeding is a major finding," said former MSU graduate student and WTI scientist Michael Sawaya. "While there have been a lot of studies showing that wildlife is using these crossings, this is the first time anyone has shown that animals using the crossings are breeding often enough to ensure that the populations on either side of the highway are not being genetically isolated."

Wildlife crossings allow free animal movement so they can cross man made barriers (roads, bridges etc.) safely. They include viaducts and underpass or overpass tunnels.

For this study, the researchers focused on the bear population in Banff National Park in Calgary, Canada. It is bisected by Canada's Highway 1. This is the first study that shows bears are efficiently using the crossing for mating and breeding with the animals on the other side of the highway, according to Nature World News.

The crossing was designed to lower the rate of collision and prevent fragmentation of wildlife population near the highway. Grizzly bears often die of road accidents. The Alberta government has listed the bears as the most threatened species.  

Along Highway 1 there are nearly 44 wildlife crossings and they form the most extensive system of wildlife crossing structures.

In order to confirm the gene flow through the population, the researchers extracted DNA from hair samples collected on both sides of the highway. They observed that the bears that crossed the highway had either sired or given birth to cubs. Some bears were even comfortable selecting a mate on the other side of the highway.

They noticed that one black male bear mated with five different female bears and sired 11 cubs.

This finding disputes assumptions that claim grizzly bears are wary of using human infrastructure.

The percentage tests revealed that nearly 47 percent of the black bear s made use of the crossing and successfully produced cubs. However, only 27 percent of the grizzly bears used the crossing for mating purposes.

The finding was published in the British journal "Proceedings of the Royal Society B."