22/05/2024
To truly thrive, bears and other wild animals need to roam widely between habitats. Wildlife tunnels, trails and bridges can help – but are they enough?
In the North West of the US, a rocky green and grey landscape juts and curves its way north to Canada, and south to Mexico. These are the Rocky Mountains, home to roving wolverine, majestic elk – and several hundred grizzly bears, whose population has been recovering thanks to efforts to reconnect their habitat so they can roam more freely.
Though huge – the tallest mountain is over 4,000m (13,123ft) high, and the range stretches a full 4,800km (2,983 miles) – the Rocky Mountains are not the wild expanse of land they once were. Towns and cities have formed in valleys, and roads have cut across the land to connect them. For wildlife, and especially the bears, this creates a problem.
Bears need space to thrive – lots of it. A typical grizzly bear needs 80 to 965 sq km (50 to 600 sq miles) to find appropriate food and meet new mates. They look for deer by the river, catch fish in mountain creeks, and forage grasses, bulbs and berries in forests and on mountain sides. A 2014 study followed a grizzly bear called Ethyl as she wound her way 2,800 miles (4,506 km) through Montana, into Idaho, and up to the border with British Columbia. But safe, connected stretches of wilderness have become hard to find, says Mark Hebblewhite, professor of Ungulate Habitat Ecology at the University of Montana, who has spent his career studying the animal inhabitants of the Rocky Mountains' peaks and valleys.
"I'm here walking above the city of Missoula, a little city of 50,000 people," he says, speaking on his mobile while out on a hike. "And I see a new development going in that's going to carve up another 600 acres (2.43 sq km) with 200 homes". These homes are needed – but they are an example of how the world's biggest, most expansive ecosystems become fragmented as humans move in.
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