Do wildlife crossings work?

There are fewer than 20 red wolves living in the wild, all in Eastern North Carolina. Once common throughout the Eastern and South Central U.S., red wolf populations have been decimated. In just the past year, five of these rare wolves were struck and killed by cars. 

This includes Muppet, the two year old red wolf who belonged to one of only two red wolf families in the wild. 

This troubling story plays out in so many ways in so many places. Wildlife all across the United States have experienced dramatic habitat loss and population declines. 

Wildlife-vehicle collisions are a key part of the problem. One pragmatic solution is wildlife crossings. But, one might ask, do they actually work? 

What is a wildlife crossing? 

Wildlife crossings help to reconnect fragmented habitats, one of the leading causes of population declines. As we build roads, cities, dams and other infrastructure, habitats are carved up and populations of animals become fragmented and isolated. Animals are then denied the ability to move as they need to – whether it be to find food, mates, shelter, or to escape weather and other seasonal threats. 

Often, these animals have no choice but to attempt to cross a busy highway. The result can be seen every day lying dead on the road. Wildlife-vehicle collisions are a large issue for wildlife and humans alike. Every year, collisions with wildlife result in hundreds of human deaths, thousands of injuries and at least $8 billion in property damage. Every day, motor vehicles kill more than a million vertebrates. 

Something needs to be done. How can we save lives, money, and the species across our country migrating towards death or extinction? Enter – wildlife crossings. Instead of risking their lives by crossing on the road, these passageways allow wildlife to travel above or below it. These crossings can exist as bridges, culverts or other overpass/underpass structures, and ensure that wildlife can safely go where they need to go for survival. 

Do they work?

The concept sounds great, but the question remains: Do they really work? Do animals choose to use the crossings? Do they actually reduce wildlife-vehicle collisions? How would the animals know where to go? 

Although there are still many unanswered questions, more and more wildlife crossings have been built, and experts are beginning to evaluate their effectiveness. In the United States, more than 1,000 wildlife corridors are in operation. 

The data thus far… (drumroll)… is very promising. Case studies from across the planet are finding that wildlife crossings indeed have a positive impact on reversing the harms of habitat fragmentation.

In Florida, wildlife crossings have increased the gene flow and prevented vehicle collisions with Florida black bears. At Banff National Park, studies show that wildlife crossings have a positive impact due to reducing roadkill, increasing food and shelter access, and even decreasing stress levels in wildlife. In Arizona, as of 2020, one wildlife overpass was used more than 6,000 times by bighorn sheep, bobcats, deer, coyotes and more.

When placed in areas of known wildlife movement, wildlife crossings with elements such as fencing have reduced wildlife-vehicle collisions by up to 97%.

Effective crossings aren’t always simple

Wildlife crossings can have significant positive impacts, but certain considerations must be taken into account to ensure they work as intended. Many animals prefer a certain type of crossing over another. For example, elk, wolves, grizzly bears and deer prefer a wide, high and short crossing, whereas species like cougars and black bears prefer long and narrow underpasses. 

Occasionally, it might take some time for wildlife to adjust to their new amenity. For animals like grizzly bears and wolves, there can be a learning curve of up to five years before they start using the structures. 

When constructing a crossing, it is important to take heed not only to how the crossing looks but where it is located. A study in California showed that a number of underpasses had been ineffective due to their location not aligning with the area’s wildlife movement. Information has been collected over many years on where and how animals move. Given this data, wildlife crossings can be placed in conjunction with where these animals naturally roam.

A successful solution

In summary, yes, wildlife crossings work. Data provide evidence that both human and animal lives are saved when we re-connect nature. Wildlife crossings are a bright spot for humans and animals.

As for the red wolves, good news is coming. Federal funding has been granted to North Carolina to support a wildlife crossing project for the red wolves. This will greatly reduce the chance of vehicle strikes with red wolves, as well as different species across the country.