Why Did the Elk (or Bear or Deer or Lynx) Cross the Road?

The Olin Studio

A design from the Olin Studio in Philadelphia would cost about $12 million and span a six-lane highway.

Nor can you ask them what would induce them to nibble that dinner while strolling across a lushly planted footbridge spanning a six-lane highway.

Getting elk to cross highways safely—and encouraging lynx, bear, deer and bighorn sheep to follow suit—was the key challenge in an unusual global contest that concluded this month.

The ARC International Wildlife Crossing Infrastructure Design Competition asked engineers, ecologists and landscape architects to come up with an overpass bridge for pedestrians of the furry sort. The goal: to encourage wildlife to roam freely across their habitat—even when that habitat is bisected by a highway.

The five finalists, unveiled last week in Denver, designed multimillion-dollar bridges that aimed to tempt animals across with tasty foliage, green valleys, gentle streams and curved walls to block out noise and vibrations from the traffic below.

Mr. Rock, who is with Michael Van Valkenburgh Associates in New York, came up with a very wide bridge planted with strips of differing vegetation giving each species its own lane to cross in: pine-tree forest for wildlife that like privacy, such as deer; a section of meadow for animals that prefer more wide-open views.

For his part, David Rubin, a partner at the Olin Studio in Philadelphia, even included a wildlife playground of sorts, made up of toppled tree trunks, to attract the American marten, a beady-eyed weasel with a penchant for scampering among dead wood.

Designing animal crossings is not a new art; in the last decade, they have become common across the U.S. But nearly all the existing crossings are underpasses—tunnels and culverts built underneath roads and out of sight.

Florida, for instance, has built a network of concrete underpasses to ferry panthers safely across roadways. Glacier National Park in Montana boasts a tree-lined underpass for mountain goats. There are tortoise tunnels in California. And the town of Amherst, Mass., guides spotted salamanders, in their annual trek from burrows to breeding ground, through special culverts that protect them from getting squashed.

But though these projects have been successful, some animals, such as elk and deer, find underpasses dark and scary and won’t use them with any regularity, ecologists say.