Animal Overpasses, Tunnels Offering Roadkill Remedy

Cameron Walker
For National Geographic News
May 12, 2004

It's one of the first rules learned in kindergarten: Hold hands and look both ways before crossing the street. But while stoplights and crosswalks can help people get safely to the other side, animals may need a bit more assistance.

Now special "ecopassages" are helping wildlife reach the other side of the road, giving them a better chance at finding food, meeting mates, and completing migrations.

According to the Federal Highway Administration, millions of animals are killed each year on U.S. roads. Roadkill has knocked an endangered cat, the ocelot, down to about 80 individuals in the U.S. The number one predator of moose in Kenai Fjords National Park, Alaska, is the car.

Along with animals, approximately 200 people each year die as a result of car-wildlife collisions.

Scientists and highway planners are now working to help get wildlife and motorists to their destinations. From salamander tunnels in Massachusetts to cougar corridors in southern California, the ecopassages that run under and above roads are allowing animals to cross roads and highways safely.

"These ecopassages can be extremely useful, so that wildlife can avoid human conflicts," said Jodi Hilty of the U.S.-based Wildlife Conservation Society. Animals that migrate can also use make use of these passages when busy roads interrupt the animals' routes, she said. Hilty has studied ecopassages in California's oak woodlands.

Perils of Isolation

For large animals with extensive home ranges, such as mountain lions, these wildlife corridors are essential to keeping the animals' territory large and their gene pools flowing.

"If a mountain lion population in even the largest of southern California's mountain ranges is isolated, it's a matter of a few decades before they disappear," said Paul Beier, a conservation ecologist at Northern Arizona University in Flagstaff.

Beier, who has studied southern California's mountain lions since 1988, has tracked the big cats with radio collars to see what their travels are like.

One of the lions he was watching, called M6, was exploring the south side of the Riverside Freeway east of Anaheim. Then, Beier found it on the other side of the freeway and found the mountain lion's tracks in both sides of the Coal Canyon tunnel under the freeway. "It was one of the most exciting days in my field research," Beier said.

As a result, the underpass has been decommissioned and restored to a more natural state, so that mountain lions and other animals can use it to get across the eight-lane highway. More recently, U.S. Geological Survey researchers have documented bobcats and coyotes using underpasses in the Riverside, California, area.

Continued on Next Page >>


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