A wildlife corridor.

Washington Department of Transportation

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Animal Crossings

Pathways built just for wildlife are making highways safer.

A hungry mountain lion steps out from a forest. In the distance, it sees a deer. But a highway stands between the big cat and its next meal. Cars and trucks speed by at 65 miles per hour. If the mountain lion wants to eat, it will have to risk its life to cross the busy road.

This problem is not uncommon. Across the U.S., animals cross traffic in search of food or new places to live. Also, highways and roads cut through the migration routes that many animals follow each spring and fall.

The result has been an alarming number of accidents. According to one study, nearly 2 million collisions took place between vehicles and animals from July 2019 through June 2020. To prevent accidents, some states have created wildlife corridors. These pathways are built under or over roads. They enable animals to cross safely.

The U.S. has more than 1,000 of these wildlife crossings—and more are being planned.

Marina Poushkina/Shutterstock.com

LOOK OUT! A black bear and her cubs cross a highway in Canada.

Over and Under

In Washington State, the I-90 highway cuts through Snoqualmie (snoh-KWAHL-mee) Pass. About 28,000 vehicles zoom through the pass each day. That could mean trouble for the hundreds of animal species that live in the area, including elk, black bears, and coyotes.

In 2009, the state began building wildlife corridors along a 15-mile stretch of the highway. Patty Garvey-Darda is a biologist with the U.S. Forest Service. She helped plan the corridors.

The project includes bridges and tunnels. The crossings are planted with grass and other plants to help them blend in with the rest of the animals’ habitat. The goal is to make sure creatures of all sizes regain the full habitat that was divided by the highway.

“We’re trying to connect the whole ecosystem,” Garvey-Darda explains.

Courtesy of Conservation Northwest

ON THE MOVE: A family of Canadian geese uses an underpass on I-90.

Safer Travels

Wildlife crossings aren’t meant to protect only animals. Thousands of drivers and passengers are hurt in collisions with animals each year.

Along I-90, wildlife corridors are doing their job. In 2019, fencing was put up along the highway to guide the animals to use crossings. Since then, Garvey-Darda says, not one large animal has been struck by a car.

Corridors have been successful in other places too. A study found that crossings along a highway in Colorado led to a 90 percent drop in collisions with moose and other large animals.

In Florida, corridors help protect endangered panthers—as well as alligators and other animals. In Vermont, crossings enable frogs and salamanders to travel safely each spring to breed.

The Road Ahead

The I-90 project is about half-finished. More crossings are scheduled to be added by 2029. Garvey-Darda says this project and others like it help wildlife and people coexist.

“This is a win-win because not only will we be safer while we travel the interstate, but wildlife populations and ecosystems will be healthier too,” she explains.

Critter Crossings

Though much of the focus in building wildlife corridors has been on big mammals, the structures also protect smaller creatures. A variety of animals has been spotted going over and under the I-90 highway. Here are a few of them.

RT Images/Shutterstock.com (pine marten); Daniel Heuclin/NaturePL.com (pocket gopher); HWall/Shutterstock.com (western toad)

1. Based on the article, what are some reasons a wild animal might try to cross a highway? 

2. What is a wildlife corridor? 

3. How did scientists in Washington State guide wildlife to use the animal crossings they built along the I-90 highway? 

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