It’s officially fall, the air is colder at night, leaves are turning bright colors, and dead raccoons dot the highways. Along with skunks, deer, coyotes and squirrels, raccoons have made quite an appearance on our roadsides in recent weeks. September and October are the times of fall dispersal for many species of mammals, when the young of the year are big enough to strike out on their own, away from mom. Many times this means seeking out new territories on the “other side of the road.” Of course this leads to an increased number of traffic fatalities for the young critters.

While many people don’t pay much attention to road kill, as a naturalist I’ve found that these flattened fauna can actually provide a great deal of information about the overall health and population size of Iowa’s wildlife. A recent road kill survey conducted in Iowa showed raccoons to be the number one animal hit by vehicles in our state. These were followed by whitetail deer, possums, cottontail rabbits, and striped skunks as the five most commonly squished critters on the highway. Eastern gray squirrels, ring-necked pheasants, Canada geese, coyotes and eastern fox squirrels also made the top 10. These wildlife species are common in Iowa and also utilize habitats which are criss-crossed by roadways.

This fall I’ve seen more coyotes hit on the road than in any other time in recent memory — all of them young (i.e. dumb) ones of course. That’s a good clue that the coyote population is healthy and growing. It also says that our rabbit population has been on the rise in the last couple of years. When rabbit numbers start to take a down turn, then predator populations will begin to drop off too.

Biologists can also use this road kill data to estimate the relative abundance of wildlife species, like coyotes. By driving the same number of miles of highway roads every day, for say two weeks each season, and recording the number and location of freshly-killed coyotes, similar to the DNR’s August roadside survey for live pheasants, you can estimate the relative abundance of coyotes from the equation: [n/l)/V] X 10,000 where: n = number of fresh road-killed coyotes; l = length of the road (km) surveyed; and V = average daily volume of traffic. In most studies, juveniles represented the majority of coyotes killed on the highway, suggesting a strong age bias. Other variables to consider are a given roadway’s average vehicle speed, the weather, season, and adjacent habitat types.

With the exception of squirrels, all of the road kill mammals we’ve seen this fall have been nocturnal or crepuscular. Because of this, drivers should pay special attention to movement from the ditches when traveling between dusk and dawn. Fall dispersal is upon us and the whitetail deer rut won’t be far behind, so keep your eyes open and stay alert when driving through Iowa’s autumn nights.