Roadkill Studies Aim to Help Animals Cross the Road
It’s not so much, “Why did the chicken cross the road?” It’s more a question of “Where did the chicken cross the road?”
At least, that is the question state transportation and wildlife officials hope to answer when they compile and release stats on roadkill in an effort to make sure animals get to the other side.
Every year, the Colorado Department of Transportation releases a report on the number, type and location of every animal that did not survive its foray onto the highway.
“We break it down by month, species, highway and if you want to go deeper, we even have certain stretches of highway,” said Jeff Peterson, CDOT wildlife program manager.
Peterson said the studies are primarily used to determine highways or areas that are proving especially dangerous for animals.
“The obvious thing is we’re finding out where animals are not successful in crossing the road,” Peterson said. “If there’s a big problem with animals, we might recommend a bridge or fencing to make it better for the animals.”
The numbers also are how CDOT decides where to place animal crossing signs, which actually are based on statistics, Peterson said.
“It’s five animals hit per year per mile,” Peterson said. “If you meet that standard, you can think about putting a sign in.”
In addition to CDOT, the information is valuable for Colorado Parks and Wildlife in examining animal movements.
“We get our biologists involved to look at animal movement and corridors to try to find the problem areas to mitigate potential safety concerns with people and obviously animals,” spokesman Jason Clay said. “Our collaboration with CDOT has been great. It’s a huge safety hazard, and is bad for wildlife and very dangerous for humans as well.”
The numbers are broken down on a larger level within CDOT’s five maintenance regions. Boulder County is included in Region 4, which includes northwest Colorado.
In 2017, 1,242 animals were killed on highways in Region 4, encompassing everything from elk to coyotes to one unfortunate mountain lion. But, year after year, one animal always presents the greatest concern.
“It’s mule deer,” Peterson said. “Probably 75 percent of (roadkill) is mule deer. It’s what you would expect, dusk and dawn in spring and fall, when they are moving.”
But while deer are the most frequent victims, the roadkill study shows porcupines, owls, badgers and even a weasel all were killed on highways in Region 4 last year. Ironically, the proverbial chicken of the road crossing jokes did not show up in the Region 4 report, though there were 43 pheasants and 10 turkeys that did run afoul of traffic.
Already in 2018, Clay said 16 species of animal in Region 4 have been catalogued.
“You just see the wide variety of animals that get hit,” Clay said. “As the state grows, people are getting more and more into wildlife habitat. It’s bound to happen, and your average person might not realize the numbers. It’s a problem.”
But who exactly gathers all the numbers? CDOT takes some of the information from Colorado State Patrol reports, but Peterson said most animal versus car crashes are not called in.
So as it turns out, CDOT gets most of its roadkill statistics from the people who have to clean it up.
“Maintenance crews record what they pick up,” Peterson said, acknowledging this means the study does have some margin for error when it comes to exact species.
“We’re not asking our maintenance guys to be biologists,” Peterson said. “They might not be able to tell the difference between birds. Or sometimes the animal might be unrecognizable due to the damage.”
This method also means smaller animals are underrepresented, since highway collisions usually reduce them to smears that maintenance doesn’t clear. For instance, Region 4 only recorded 38 prairie dog deaths and one squirrel death, even though Peterson said the actual number is undoubtedly higher.
“A lot of smaller animals are underreported,” Peterson said. “They can’t scrape up every prairie dog.”
Because of the method of gathering the statistics, Peterson said they aren’t necessarily useful for identifying wildlife trends. But they are especially useful in figuring out if mitigation efforts are working. Peterson said a series of underpasses and overpasses recently installed on Colo. 9 near Kremmling reduced animal deaths by 90 percent .
“Is a big significant mitigation effort being effective? That’s what those numbers are really useful for,” Peterson said.
And, of course, they are a constant reminder for motorists of just how often animals cross the road.
“It should be a constant reminder to be vigilant from driving,” Clay said. “And obey the signs CDOT puts up. They have those signs for a reason, and there are numbers behind it.”
Mitchell Byars: 303-473-1329, email@example.com or twitter.com/mitchellbyars