Forest Preserve District of Cook County, Illinois
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Traffic Toll of Wildlife
Nature Bulletin No. 242-A   October 29, 1966
Forest Preserve District of Cook County
Seymour Simon, President
Roland F. Eisenbeis, Supt. of Conservation

The Jains, a religious sect in India, take a vow "not to kill". A Jain wears a cloth over his mouth for fear he might unknowingly swallow a gnat or a fly, and carries a broom to whisk small creatures from his path. We Americans go to the other extreme. We brush off the fact that, on our highways, we have carelessly killed and crippled more of our own people than two world wars. But that is not all. Highway traffic is a major cause of death to our wildlife.

Until the advent of the automobile, a few animals lost their lives on public roads. Occasionally a turtle or a snake was injured or crushed in the horse-and buggy days, but rarely a bird or mammal. The Model T Ford and its contemporaries, with an average speed of 25 miles per hour on the gravel and dirt roads of their time, ran down a few rabbits, possums, skunks and roving house cats blinded by their headlights, but there were few daytime casualties except sparrows, red-headed woodpeckers, and farmers' poultry.

Then, during the 1920' s, much of our present network of paved highways was built. In the late twenties, fast cars and trucks began to appear in numbers and, presently, most traffic was moving at 50 miles per hour, more or less. Then, a sharp upturn in the traffic kill of wildlife began, which continues to increase.

The first study of this traffic hazard was made by W. P. Flint of the Illinois Natural History Survey. He kept year-round records during 1930, 1931 and 1932 of all wildlife and livestock killed on a 25-mile stretch of state highway between Urbana and Oakwood, Illinois. An average of one dead animal per day was found on each two miles of pavement. From April to October were the peak months. Of the total, almost half were English sparrows, approximately one-tenth were chickens, one-tenth were rabbits and one-tenth were gophers. Less than one-third were species useful to man: songbirds, domestic poultry, game animals and fur-bearers.

Another study of this toll of animals was made on Cook County highways in 1946 and 1 947 by forest preserve naturalists. A day-to-day tally of the casualties among the larger forms of animal life was kept for a total of 21,000 miles about equally divided between highways in rural regions, through suburban towns, and those traversing or bordering our forest preserves. For various reasons but principally on account of the large volume of fast traffic on the many 4-lane pavements, it was not possible to count small animals such as mice and songbirds, or even larger ones. Others were thrown off the pavement or, badly injured, crawled away to die. We may have seen only a fifth or possibly a half of the total.

Even so, here the picture is much different than in rural downstate Illinois. Rabbits were by far the most numerous, followed by squirrels, cats, possums and skunks -- in that order. On roads through suburban towns and rural regions, the percentage of cats killed increased sharply. Dogs, raccoons, gophers, groundhogs, mink, muskrats, a few weasels, and even one red fox, were the other large mammals counted. Pheasants, because of their size, were the most common birds found killed. Domestic poultry was uncommon. It was found that the annual kill by traffic of game and fur-bearing animals, on highways passing through or bordering our forest preserves -- a minimum of 3000 animals -- is about the same, per square mile of land, as the annual kill by hunters and trappers in downstate Illinois. To wildlife, the automobile is as deadly as the shotgun.

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