Roadkill is a 20th Century phenomenon, which is to say that we did not have it in the 19th Century when the roads were populated by horses and carriages.
Oh sure, we had some train kills -- deer and moose and cows and buffalo, but that's trackkill, not roadkill. And, of course, some horses died on the road from exhaustion or being shot, but they too were not roadkill as we define it here -- animals dying from vehicle impact on the road.
In fact, roadkill is probably the wrong term, even if it is the one we use. Carkill is what this really is; the road, after all, is simply a passive observer.
The problem with the term "carkill," is that it puts us in the picture. Roadkill, however, is a term that conveniently assigns millions of drive-by deaths to an inanimate object. It is a comforting term that obsolves us of guilt.
Today, the Mercury Cougar (Automobilus detroitus) does some of the pruning work once done by the wolf (Canus lupus). Which is not to say Ford, Chevy, Toyota, Volvo, Mack Truck, and all the rest are not doing their part as well. They are.
Roadkill is not a small biological phenomenon, it is a big one. In my small state of Virginia, there are over 35,000 deer-car impacts a year. In Michigan, deer impacts are so pervasive (over 55,000 a year), that they use deer roadkill data to determine the deer population in the woods. In Pennsylvania, another 40,000 deer a year fall under the wheel. What's the national tally? Who know? The number 350,000 is tossed around, but that seems low. That said, not all states have as many deer as Virginia, Pennsylvania and Michigan, or as many drivers on dark or twising roads. So who knows? Whatever the number, it's clear that it is a lot.
Though I have no doubt that Darwinian forces are slowly playing out between animals and cars, the time-frame is still far too short. As a result, as brilliant as a squirrel is at figuring how to get to, and jimmy open, a bird feeder, it is still completely flummoxed by squealing tires and 4-cylinders. As a result, squirrels die in droves from vehicle impacts -- perhaps 40 million a year according to one back-of-the-napkin bean counter.
A few more sobering roadkills numbers, and some descriptive reasons as to why some animals are more likely to die on our highways than others:
- Dogs: 1.2 million dogs are killed on U.S. roads every year. Most of these dogs are killed in the daylight while chasing a ball, child, cat, or squirrel. Fences and leashes keep dog alive. No fence and no leash, and the result is predictable.
- Cats: Cars kill about 5.4 million cats per year -- more cats than are killed in all U.S. animal shelters. Most cats are hit by cars at night.
- Snakes: Snakes are cold-blooded and will warm themselves on asphalt, especially on poorly-traveled rural roads. Because snakes are small and easily obliterated by tires, there are no good numbers, but they are huge.
- Opossums: Opossums feast on roadkill, a habit that results in about 19 million opossums a year getting squashed. Possums are naturally slow, come out at night, and will often freeze in the headlights of a car.
- Skunks: When threatened, a skunk's natural defense is to turn its back and spray -- a technique that does not work too well with cars. Most skunks are hit at night.
- Groundhogs: An estimated 5 million groundhogs or woodchucks get hit by cars every year. Groundhogs are diurnal, but because so many den along roadside embankments in order to take advantage of soft dirt, good drainage, fewer predators, and good forage, they are often living just yards from traffic. Sure this is maladaptive, but groundhogs have not been programmed with cars in mind.
- Raccoons: Raccoons frequently scavenge in roadside water ditches, are not too fast, are fairly belligerent, sometimes travel in trailing family groups, and hunt at night. Which is a nice way to say their are a lot of vehicle-raccoon impacts -- perhaps 10 million a year, maybe more.
- Fox: Red fox are field-and-edge creatures, and are much more likely to be hit be a vehicle than a Gray fox which will generally be found in deeper woods and rocky areas. That said, both Red and Gray fox are night time scavengers, and as such are prone to being struck on the road while feeding on the carcass of a snake, possum, rabbit or squirrel previously struck by traffic. The saving grace of a fox is that they are very fast and extremely wary -- the two chief reasons you see fewer dead fox and coyote than you do dead raccoons and possums.