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
TRAFFIC TOLL OF WILDLIFE
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
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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Update: June 2012