I GREW UP IN Littleton, Colorado, a suburb of Denver that was forcefully inserted into miles of open prairie land back in the late ’80s. This is where the sprawling eastern plains meet the Hogbacks, the very beginnings of the Rocky Mountains. 25 years later, we still have more open space than most areas of suburban Denver, but the buildup of a major highway and a network of suburbs has disconnected the deer, coyotes, bears, and mountain lions from their natural thoroughfare between the plains and the mountains.

Before the buildup, baby deer would run down the street in the morning if you could wake up early enough to catch them, and coyotes howled every night. Nowadays such sightings are rare, and the vast majority of these animals either won’t risk the highway, or get hit by cars in the process. The first elk I’ve seen in years made his way into the neighborhood this summer to snack on our neighbor’s unmowed lawn, and he looked mightily confused about how he managed the maneuver.

Here are 6 ingenious wildlife crossings that help make the journey as natural as possible for the four-legged travelers of the world.

1

Ecoduct, Netherlands

The Dutch are revolutionizing wildlife crossings and trying to put an end to the habitat fragmentation caused by human made structures.

2

Banff National Park, Canada

This park takes the prize for keeping its wildlife safe, with 41 different wildlife structures that help bears, elk, and cougar cross the Trans-Canada Highway over 200,000 times per year. To see an aerial shot of one of these overpasses, click here.

Photo: WikiMedia

3

I-90 in Washington, USA

This is a mockup of an overpass being designed for highway improvements near Keechelus Lake. Construction is set to begin in 2014 at the earliest. Officials are using the Banff overpass for inspiration.

Photo: WSDOT

Intermission

10 animals your children will never see

10 great animal migrations to witness

What it takes to be a wildlife photographer [PICs]

4

Grevesmülen, Germany

The Germans call this the “Green Bridge” over the A20 highway.

Photo: Wikipedia

5

Montana, USA

An “animal bridge” helps wildlife cross the road in one of Montana’s national parks.

Photo: The Pedigree Artist

6

Christmas Island National Park, Australia

How many places in the world can you see a sign for "crab crossing"? Christmas Island's red crabs make one of the 10 great animal migrations you can witness.