When any type of animal stops trying to cross a road due to fear, the highway has become a barrier, and their species will be at risk of dying out. This is because the animals’ habitat is now fragmented, or broken into pieces, and so they can no longer breed and hunt for food in a healthy way.
It is up to humans to help animals cross our roads, or else we may lose them forever.
Road Ecology and Wildlife Crossing Structures
For years, people around the world have been working to make roads safer for both animals and humans. They study and practice what is known as road ecology.
“The solution to addressing issues of wildlife and highway interaction is two-pronged: fencing plus crossing structures,” says Terry McGuire, a highway engineer now retired from Parks Canada and a road ecology expert. “It has been shown through research that one does not work as effectively without the other.”
While some animals take years to become comfortable using crossing structures, others can become comfortable with them quite quickly. Fencing helps guide wildlife to crossing opportunities, saving individual lives and also helping populations thrive.
Fencing and crossing structures have been used successfully in countries all over the world, from France and Germany to Singapore and South Korea. Our North American neighbors, Canada and Mexico, have also created effective crossings. Now, states like California, Colorado, Texas, Washington and Utah are focusing on road ecology too.
Safe Passage: The I-40 Pigeon River Gorge Wildlife Crossing Project is working to make roads safer for both wildlife and people near Great Smoky Mountains National Park.
Passed Down Through Instinct
Long before humans ever thought about building roads for their own travel, animals had created ancient trails, often near sources of water. They followed these trails by instinct across the land to get many things they needed to thrive. Food, shelter, and mates were high on the animals’ list of needs.
Now, our roads crisscross those same ancient trails in every part of the world. But wild animals still try to use their old routes, because they still need to get a variety of foods and find healthy mates outside their own families.
The more vehicles travel on roads, the harder it is for wildlife to cross successfully. As long as animals keep trying to cross, humans can also be injured or killed in the accidents or collisions that result.
Types of Crossings
Old-fashioned road signs don’t cost much to put up and can help make drivers aware an animal may be crossing and remind them to go slower for safety. They work best in parks where speed limits are already low, but still they cannot save animals’ lives or prevent collisions.
These are electric signs that turn on when an animal is crossing or starting to come into the road. They can help by getting drivers to slow down and watch for wildlife. They are a bit more expensive than basic signs, work best on small roads without much traffic, and can only detect large animals.
Made of metal, cement, or plastic, culverts may be round or elliptical in shape and cost less than many other types of crossing structures. They are used well by many small species to pass under the highway. Coyotes and bobcats like them too, but larger species usually reject them because they are so dark and may seem like a trap.
Offering more space and better footing than round culverts, box culverts come in many sizes and can save the lives of small, medium, and large animals. In the southwestern US they channel water from flash floods and allow many species to cross under roads as well. They have been shown to work for black bear and Florida panther for a modest cost. These types of structures can be designed to aid crossing for turtles, snakes, frogs, salamanders and other reptiles and amphibians.
These are made of curved steel plates that are usually brought to the road and put together there. They can often work just as well as more expensive structures for megafauna such as bear, deer, and elk—and for mountain lions in the west. As with culverts, some animal species might refuse to go into a multi-plate arch because of the lack of natural light and feeling of being confined or fear of being trapped.
In places where it is critically important to connect wildlife habitat, such as migration routes, open-span bridges are highly recommended. A more expensive option than culverts or arches, these bridges can cost more than one million dollars each. In the western states and Canada, they have been seen to work well for large wildlife including bear, deer, elk, mountain lions and wolves—and to help smaller species as well.
When animals travel, they often follow water drainages, so making a bridge extension is one of the most effective ways to help wildlife to cross highways. Animals of all sizes are comfortable passing under bridges because, unlike in a culvert or arch, there is plenty of natural light and they do not feel confined. Bridge extensions can be expensive, but since transportation departments often make road repairs, creating wildlife crossings can become a part of that process, saving animals’ lives.
Because they can work well for the most species, wildlife overpasses may be the best solution to wildlife crossing needs. Species like moose and antelope that will not cross underneath the highway can thrive using an overpass. Though this is the most expensive type of wildlife crossing structure, it has been used with great success to save animal lives in Europe and Canada. Overpasses are now being considered in states including Colorado, Washington, and Utah among others.
Variety is Important
It is important to locate wildlife crossings where animals wish to cross the road, not just where it may be easy or convenient from a construction perspective. Scientists and researchers help road planners know where animals try to cross by studying wildlife mortality, collision data, migration routes, and the geographical terrain of the area.
One type of crossing does not necessarily meet every animal’s needs and, ideally, a combination of various crossing types should be provided, spaced out in such a way that animals do not need to travel great distances to find a crossing.
Most wildlife shy away from anything that looks like a trap, and so, at first, animals may not want to use wildlife crossing structures. Having trees and plants close to the structure reduces light and noise and gives animals’ protective cover. Fencing must be put in place to direct them to a new crossing structure, or they may choose to cross the highway rather than use something unknown. Sometimes an animal trying to use a structure will find itself in the road, and so an escape ramp must be close by so it will not be trapped. All of these aspects need to be considered as part of the planning process for a successful wildlife crossing.
Source: Bill Ruediger, Wildlife Consulting Resources, Safe Passage: A User’s Guide to Developing Effective Highway Crossings for Carnivores and Other Wildlife