Anyone who has ventured down one of Washington’s country roads in search of a colorful display of turning leaves has probably noticed another decidedly less scenic hallmark of autumn: The battered, decomposing bodies of deer, elk, coyotes and other animals that pepper the highways this time of year.

A quietly maintained state database of animal casualties on state roads reveals that this seasonal pairing of the glorious and the grisly is no coincidence. In Washington, October is roadkill season.

Each year, road maintenance crews working for the Washington State Department of Transportation remove an average of about 3,500 deer and elk carcasses from Washington highways, according to the WSDOT website. These collisions aren’t just harmful to wildlife — they result in an average of 1,190 human injures and two fatalities per year.

For almost a decade, road maintenance crews at the Washington State Department of Transportation have catalogued the age, gender, location and species of each animal they remove in the “Wildlife Carcass Removal Database.”

This database, which can only be viewed by special request, can be searched by time of year, highway, or type of animals. Nine years’ worth of data for Pacific and Wahkiakum county roads reveals some interesting patterns and occasionally surprising things about which animals get hit, and where they get hit.

Local roadkill facts

• Many animal deaths in the region are concentrated just outside of cities or towns. For example, about a third of Wahkiakum County animal deaths on State Route 4 took place in a three-mile section immediately to the east of Cathlamet.

• Additionally, a roughly four-mile stretch of State Route 4, between the Wahkiakum County line and the town of Naselle, and a roughly five-mile-long stretch of Highway 401 that terminates in Naselle had by far the highest concentrations of animal deaths of any state roads in Pacific County.

• On State Route 6, which lies partially in Pacific County and partially in Lewis County, about 80 percent of animal-vehicle collisions happened on the Pacific County segment, even though it constitutes only about one-third of the total length of the road.

• While Highway 101 has the highest average number of animal deaths each year because it is the longest road in the county, the average number of deaths per mile on this road is actually relatively low.

• Overall, black-tailed deer are hit far more often than any other species, but there are a few exceptions. Fifty-four percent of all Pacific County elk deaths that have been recorded over the last nine years took place on two small stretches of road on State Routes 4 and 401.

An incomplete picture

The database was created as a way to gather information about animals’ patterns of movement, motorists’ driving habits, and road safety, said Kelly McAllister, a biologist for WSDOT. As the transportation agency’s resident expert on roadkill, it’s his job to maintain the database, study animal behavior around state roads, and make recommendations about how to reduce vehicle-animal collisions.

McAllister cautions that the database is far from perfect. Due to several pitfalls of the data-gathering process, the real number of animals casualties is likely much higher than the database indicates.

For one thing, the database is “a reflection of the large mammals — almost most exclusively deer and elk — that are picked up by maintenance staff,” McAllister said.

The crews rarely remove small animals, because they aren’t reported as often and they don’t create a hazard for drivers. So even though creatures like raccoons, skunks and opossums are regularly hit, the database doesn’t reflect that.

Additionally, animals that die on non-state roads aren’t included, and animals that wander off of a road before dying generally fall through the cracks. And some animals are simply never reported, McAllister said.

Finally, WSDOT crews do not always report their findings.

“There’s a fair amount of variability in terms of who does report it and who may not. I’m sure when (road crews) get really super busy with snow removal or trees knocked on roadways, forgetting to report carcass removal is probably fairly easy to do,” McAllister explained.

But, “given those limitations, it still is our best representation for where we’ve got problems — where animals are being hit chronically, regularly year after year in numbers that stand out relative to everywhere else in the state,” McAllister said.

Data is put to real use

By studying when and where animals die, researchers can identify patches of road that are particularly dangerous for animals — and perhaps for drivers too. WSDOT officials use the data to determine how to establish spending priorities, and decide where additional safety precautions are needed.

Most often, this means putting up the ubiquitous yellow diamond-shaped sign featuring the silhouette of a buck. Increasingly, digital signs with changing messages are being used to alert drivers to the presence of large mammals.

In a few cases, the data has led WSDOT to invest in more extensive measures to reduce animal collisions. On Highway 97, north of Wenatchee, and on a stretch of road between Cle Elum and Ellensburg, the frequency of collisions was so severe that WSDOT resorted to measures such as installing eight-foot-tall barrier fences and creating alternate ways for animals to cross the highway.

McAlliser said researchers are also using the data to supplement the computer modeling programs they use to track animal movement around highways.

“It’s very real data,” McAllister said, “We use the roadkill data as a kind of a validation step.”

Identifying patterns

Together, the modeling and roadkill data make it possible to quantify and better understand the roadkill patterns and trends that many locals have probably already identified in an informal way.

“Spatially there is a lot of consistency to some of the problem locations. …You just about know you’re gonna see elk numbers along the Willapa Bay,” McAllister said.

The data also shows that the Pacific County areas where animal casualties are most common fit a profile that contributes to animal deaths all over Washington. Animals are most often killed “where you have roads that carry an intermediate traffic volume — an average of 5,000 to 10,000 cars per day in non-urban environments,” McAllister said.

Large mammals know enough to avoid populous city streets and heavily used highways like I-5, where the traffic screams by at high speeds. On low-traffic country roads, their chances of crossing without encountering a car are pretty good.

But rural commuter roads like State Route 401 have a combination of high animal populations and consistent traffic that regularly proves deadly for deer and elk.

And as for the local spike in seasonal deaths, it turns out that this is a statewide phenomenon with a perfectly logical explanation.

Autumn is mating season for deer. And when deer have love on the brain, McAllister said, traffic is the last thing on their minds.

“The males are suddenly feeling the hormones running and they’re looking for females,” McAllister said, “They tend to have very little sense of their surroundings.”

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