Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things


Wild Things

Animals get safe spots to cross the road — and car collisions drop

pronghorn

After overpasses and underpasses for pronghorns and other wildlife were constructed on a highway in Wyoming, vehicle collisions with animals dropped precipitously, a new study reports.

Sponsor Message

U.S. 191 is one of the driving options for people headed to Grand Teton or Yellowstone National Parks. But the road also cuts through prime territory for mule deer and pronghorns. And cars and large wildlife don’t usually mix well. When they do tangle, the cars end up heavily damaged, and the animals end up dead.

In an effort to reduce this conflict, the Wyoming Department of Transportation spent nearly $10 million to install two overpasses and six underpasses, along with deer-proof fencing, on sections of the highway near Daniel Junction in 2012. The sites for the passes were chosen based, in part, on the migration patterns of mule deer and pronghorns through the area.

Shortly after the installation, the animals were seen using the crossings, and vehicle collisions appeared to decline. The project was labeled a success. Now, an analysis of the project finds just how successful it has been: Car collisions with pronghorn have disappeared entirely and those with mule deer have dropped by 79 percent, Hall Sawyer of Western Ecosystems Technology Inc., and colleagues report May 16 in the Wildlife Society Bulletin.

Two digital cameras were installed at each overpass and one at each underpass to monitor wildlife using the crossings during the spring and fall migration periods in 2012 through 2015. Thousands of animals started using the pathways, and each year, more and more animals crossed the highway using these safe paths. Over the years, 40,251 mule deer and 19,290 pronghorn made their way through the passages.

Of the mule deer passing through, 79 percent used the underpasses. But among pronghorns, 92 percent took the overpasses. This confirms something that researchers had thought would be true but never really had any data to back up. They figured that ungulates such as pronghorns that live in open areas and are heavily reliant on vision to detect predators should prefer overpasses, because the structures would allow the animals to have better vision and movement. The new finding supports this, at least for pronghorns, and shows that building overpasses, which are more expensive than paths beneath highways, really is necessary for some animals.

This area of U.S. 191 was one of the worst for wildlife vehicle collisions before the crossings were built, averaging 85 per year from 2005 to 2012. By the third year after the installation, though, collisions had dropped to just 16 per year.

When the crossings were put in place, the Department of Transportation claimed that, by preventing vehicle collisions, the project would essentially pay for itself in 20 years. But this project has been so successful, the team calculates, that a crossing could pay for itself in just 4 years. And then, of course, there’s the benefit for the wildlife itself, which can now more easily and safely move through the landscape.

The team does note that Wyoming did have to make a few adjustments to the project to accommodate human behavior. The overpasses are edged with high berms to prevent animals from seeing the highway, but those berms proved tempting to ATV users and motorcyclists. Because this activity is damaging to vegetation and could reduce effectiveness of the crossings, the Bureau of Land Management had to post signs warning people away.

And when the crossings first went up, some canny hunters figured that the overpasses were good spots to find hundreds of pronghorn; hunting is now banned within 800 meters of a wildlife overpass. 

Animals,, Conservation

Counting cats is hard, but we know the numbers aren’t good

By Sarah Zielinski 9:03am, May 27, 2016
Recent studies highlight the difficulty of counting big cats, but even imperfect counts show that these species are in trouble.
Animals

For baby sea turtles, it helps to have a lot of siblings

By Sarah Zielinski 8:31am, May 23, 2016
After hatching, baby sea turtles must dig themselves out of their nest. This requires less energy if there are lots of siblings, a new study finds.
Animals

These mystery mounds are actually giant piles of earthworm poop

By Sarah Zielinski 8:33am, May 20, 2016
The grassy mounds that dot a watery landscape in South America are created by giant earthworms, a new study finds.
Animals

The bizarre mating ritual of a bee parasite

By Sarah Zielinski 8:41am, May 18, 2016
Stylops ovinae insects — parasites found in mining bees — have short lives filled with trauma.
Animals

Vultures are vulnerable to extinction

By Sarah Zielinski 8:36am, May 11, 2016
Life history makes vultures more vulnerable to extinction than other birds, a new study finds, but humankind’s poisons are helping them to their end.
Animals

Crocodile eyes are optimized for lurking

By Sarah Zielinski 2:28pm, May 6, 2016
Crocodiles hang out at the water’s surface, waiting for a meal. A new study shows their eyes are optimized for spotting their prey from this position.
Animals,, Oceans

Cause of mass starfish die-offs is still a mystery

By Sarah Zielinski 11:53am, May 5, 2016
Sea stars off the U.S. west coast started dying off en masse in 2013. Scientists are still struggling to figure out the cause.
Animals

Chemical behind popcorn’s aroma gives a bearcat its signature scent

By Sarah Zielinski 9:20am, April 28, 2016
Bearcats smell like popcorn. Now scientists now why: The chemical responsible for popcorn’s alluring scent has been found in bearcat pee.
Animals

How animal poop could be key in solving echidna mystery

By Sarah Zielinski 2:30pm, April 26, 2016
The western long-beaked echidna hasn’t been seen in Australia in 10,000 years. But DNA in scat could reveal its presence.
Animals,, Oceans

Scientists find a crab party deep in the ocean

By Sarah Zielinski 9:00am, April 18, 2016
A trip to check out the biodiversity off the coast of Panama revealed thousands of crabs swarming on the seafloor.
Subscribe to RSS - Wild Things