"The Amazing Tunnels, Trails and Bridges Built Especially for Bears"

The Tunnels, Trails, and Bridges Built Especially for Bears

Wildlife corridors are helping grizzly bears roam more freely in the Rocky Mountains.

For bears and other wild animals to truly thrive, they need to roam widely between habitats. Wildlife tunnels, trails, and bridges can help – but are they enough?

In the northwest of the US, the Rocky Mountains stretch from Canada to Mexico. This rugged landscape is home to wolverines, elk, and several hundred grizzly bears, whose population is recovering thanks to efforts to reconnect their habitat. Though huge – the tallest mountain is over 4,000m high, and the range stretches 4,800km – the Rockies are not as wild as they once were. Towns and roads now cut across the land, creating problems for wildlife, especially bears.

Bears need lots of space to thrive. A typical grizzly needs 80 to 965 sq km to find food and meet new mates. They hunt deer by rivers, catch fish in creeks, and forage for grasses, bulbs, and berries in forests and on mountainsides. A 2014 study tracked a grizzly bear named Ethyl as she traveled 2,800 miles through Montana, Idaho, and up to the Canadian border. But safe, connected wilderness is hard to find, says Mark Hebblewhite, a professor at the University of Montana.

"I'm here walking above the city of Missoula," he says, "and I see a new development going in that's going to carve up another 600 acres with 200 homes". These homes are needed, but they also fragment one of the world's largest ecosystems.

Helping Animals Roam and Connect

One solution is to help wildlife cross from one protected area to another. This can be done with highway underpasses or overpasses, also known as bear tunnels or bridges. Another solution is to prevent areas from being developed so they can connect two protected areas. Known as wildlife corridors, these connecting strips are gaining more attention. They have begun to reconnect habitat for tigers in Nepal, bees in Britain, and deer in the Netherlands.

Ecological corridors are important because research shows most protected areas are too small to maintain all species and ecological processes, says Jodi Hilty, president and chief scientist at Yellowstone to Yukon (Y2Y). Y2Y aims to build connections between important habitats along the Rocky Mountains. The Yellowstone to Yukon region spans 1.3 million sq km, from Yellowstone National Park in Wyoming to Canada's Yukon Territory. Since 1993, the Y2Y team has turned this land from a disjointed patchwork of protected areas into a more connected space for animals. Now, 95% of the land is classified as "wild," though only about 16% is protected.

Mountains are ideal for bears because their diverse landscape provides food, shelter, and safety from humans. Grizzlies are omnivores, eating both meat and plants. They shift their diet with the seasons, which means they need to move to find new foods, explains Hebblewhite.

The Impact of Wildlife Corridors

In 1985, there were only 200 grizzly bears in the Yellowstone region. By 2010, this number had risen to 600. Hunting restrictions helped, but connecting scattered habitats was also crucial, says Hilty. Mountains help many kinds of wildlife, providing homes for vulnerable species and sanctuaries during climate change. The Rocky Mountains are home to threatened lynx, swans, bats, wolves, and mountain caribou.

However, private lands in valleys are dangerous for bears. Rubbish bins and chicken coops attract bears and lead to conflicts with humans, often resulting in the bear being shot. Coexistence work aims to help bears pass through without trouble, whether in rural or urban areas, says Hilty. About eight grizzlies a year are killed by cars in Alberta, Canada, while 12 are shot.

Helping bears cross roads safely is a key intervention. Scientists use remote cameras to study where animals try to cross highways. Findings help determine where to build bridges or tunnels, often with fences along the nearby highway. Such crossings reduce collisions by 80-97%. The team has built 127 wildlife crossings, supporting various species from bears to salamanders. More crossings are in progress.

Isolation is another threat to bears. Highways prevent bears from meeting and mating, shrinking the gene pool. Wildlife corridors help them meet new mates, improving population health.

Respecting Wildlife and Communities

Whisper Camel-Means, a member of the Qlispe tribe and a wildlife biologist, emphasizes the importance of tolerance. New residents need to understand that if they see a bear, they should go inside and let the bear continue its journey, not have it trapped or killed. Respecting wildlife is also about respecting communities that have coexisted with these animals for a long time.

Conservation projects should avoid undermining local communities. Indigenous tribes were pushed off their land when Yellowstone National Park was established. A historical treaty has protected land rights for the Salish and Kootenai communities. Currently, 25% of the Y2Y project is managed or co-managed by Indigenous people, and Hilty hopes this will increase.

Efforts to help bears also protect other species. The Rocky Mountains are home to many rare plants and animals. Conservation efforts focus on creating corridors that will remain effective as the climate changes. Understanding ecological connectivity helps us understand how the natural world works and our place in it, says Hilty. 

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