U.S. Fish & Wildlife Service

Sacramento Fish & Wildlife OfficeServing the people, conserving the fish, wildlife, and plants of California

A Unit Of The Pacific Southwest Region

Helping Wildlife Avoid the Rivers of Predators

August 16, 2012

Multiply the dead animals you see on the side of the road by the total of days you and everyone else drives.  That’s a lot of Roadkill Road Ecology is the study of the effects roads have on nature and the science has come a long way. Photo Credit: John Cleckler/USFWS

Almost everyone has either driven or been the passenger in a car at some point, and while you were in that car, what did you see on the road? There’s the constant flow of cars, the lanes, the signs, and the road kill. It’s always there. A raccoon or a squirrel, maybe you didn’t see it but could smell a deceased skunk somewhere close. Now imagine that one dead animal on the side of the road and add up the total days a week you take a drive. Now a year and multiply that number by the number of people who drive in the world. That’s a lot of road kill.

Ok, so road kill isn’t a pretty picture. That’s just the thing, Road Ecology is the study of the effects roads have on nature, i.e. road kill. Ever heard of Road Ecology? No? I hadn’t either until speaking with John Cleckler from the U.S. Fish and Wildlife Service’s Sacramento Office. John was kind enough to give me an overview so that I could give you- the average public citizen- a little knowledge about the rising new science.


The animals in areas around roads see a multitude of effects due to the roads around them and each has a strong impact. Photo Credit: John Cleckler/USFWS

Roads have various effects on the animal community that surrounds them. They are a constant threat. They can cause behavioral disturbances in animals, behavioral barriers, erosion, change of landscape, and chemical run off from the cars. The animals in the surrounding areas see a multitude of effects due to the roads around them and each has a strong impact.

  • Behavioral Disturbances and Barriers: When an animal such as a salamander is travelling to a pond its instinct is to go directly to the pond- it doesn’t comprehend the idea that there could be a highway in between it and its destination. Salamanders don’t have a GPS on them that can guide them away from harm and so they walk right into the street. The salamander, raccoon, or deer experiences a disturbance in their natural behavior when they enter that road/freeway. Unaware of what to do they walk right into traffic. These ‘barriers’ in their natural habitat are harmful to not only the animals but to drivers as well, who swerve to protect them, or hit them and in turn are harmed.
  • Changing Landscape: Most of our roads have been here for a while, so we don’t always think about their consequences, but there are a few new roads here and there that are added to our system of transportation. These new roads have an impact on not only the animals themselves but on their habitat as a whole. When a new road is put in, it causes a change in landscape. The road could potentially cut a forest in half or divide a population of species in two. These changes could cause a decrease in animal population or cause a species to evolve at a different rate than its other members.
  • Chemical Run Off: The chemicals our cars leave on the road are dangerous to the habitat of all animals. These chemicals are washed off the road from rain or spills and they get washed into the rivers and the soil of the surrounding area. The chemicals have been known to affect amphibian breeding and cause forced evolution in salamander populations. These chemicals also have affected the distance that plants can grow in distance to the road, and have led native plants to being outcompeted with nonnative plants that adapt better to exhaust from the cars.

Wildlife crossings are tools for animals to get from one side of our roads to the other. There are various types of wildlife crossings for different species of animals. Photo Credit: P. Cramer, USU, UDWR, UDOT

Wildlife Tunnels and Crossings

While discussing wildlife tunnels/crossings, John Cleckler said, “Roads are like rivers of predators to all species of wildlife.” To us, a road is a tool of transportation, a means of getting from point A to point B. However, that tool may just split up point A and point B for creatures like salamanders and deer. Each year the road kill adds up, and it isn’t always just a little chipmunk on the side of a freeway. There are animals anywhere from endangered butterflies to elephants that have suffered from car collision around the world.

Animals can’t cross a road safely without their own tool - which is just where wildlife crossings come in handy. They can be located above or below the road in areas that are known for condensed animal crossings.

California’s Progress

California is behind the national trend in part because most animals here that need these crossings are smaller animals like amphibians.  Those are cheaper but harder to sell to the public. Photo Credit:  John Cleckler/USFWS

There are a few of these animal crossings in California. In Southern California there are drainage culverts known to be used by wildlife, and there have been multiple crossings made for animals throughout the state such as under the road tunnels for California tiger salamanders. John Cleckler says with the rising science of road ecology and all of the wildlife tunnel/crossing projects throughout the world “[California] can’t help but be pulled along a little bit.”

However, California is behind the curve when it comes to wildlife crossing/tunnels installation. While there is talk of animal overpasses being built in both Northern and Southern California, most of the animals of California that are in need of these crossings are smaller animals like amphibians and wildlife crossings for these animals are harder to sell to the public.

Getting interest and support for a big fuzzy bear or a pretty fragile deer in need of a crossing is generally easier than building up interest for a salamander or a toad. The crossings/tunnels cost a lot of money and even though those for smaller animals cost less, their cause is harder to raise money for.

What You Can Do to Help

I’m not about to tell you to stop driving to school, or to stop commuting between cities or using your cars because, let’s face it, that will never happen. Our society depends on mobility and transportation. However there are a few things the public can do to help reduce the effects of roads on nature.

  1. Learn – Educate yourself about the wildlife in your area, whether or not there are any crossings or tunnels near you, and what coming road projects would benefit from a wildlife crossing. A good place to start is Road Apple on Facebook-https://www.facebook.com/pages/Road-Apple/216338871750856. Knowledge is the best first step to take!
  2. Report – The California Roadkill Observation System is the first statewide roadkill reporting web site. It allows the public throughout California to record their observations of deceased animals and the context of their environment and through CROS helps increase the knowledge of potential wildlife car collisions.  Visit http://roadecology.ucdavis.edu/ to participate.
  3. Support – There is not enough money to fund projects like wildlife tunnels/crossings throughout the state of California, so you can always help by finding or writing grants to help fund a local project. And when you hear of a project in your area proposed to help wildlife in this way, stand up and support it.

Your voice matters.

Story by Ashley Cotter, Summer Intern, U.S. Fish and Wildlife Service, Sacramento Office

Last updated: November 9, 2017