Roads Take a Toll on Wildlife

Wildlife carcasses litter the sides of rural roads. Researchers in one study spotted an average of 14 vehicle accident victims for every 100 miles they drove. On the southern Great Plains of Kansas, Oklahoma and Texas, they added up 1,412 mammal roadkills in 10,250 miles of driving over three years.

Their figures don't include unidentifiable carcasses or animals that crawled out-of-sight before succumbing from a collision. So the tallies underestimate the total carnage on what some people have termed "long, narrow slaughterhouses".

The University of Oklahoma study identified 18 species of mammals lying dead along roads that pass through woodlands, prairie and rural countryside. Nearly all (85 percent) of the kills were of four species: striped skunk, Virginia opossum, nine-banded armadillo and northern raccoon.

Two of these mammals resort to survival strategies that don't adapt well to avoiding collisions. Armadillos and skunks won't readily get out of the way of on-coming vehicles. Armadillos jump straight upward when startled, while skunks stand their ground once realizing they can't outrun a car.

Other road deaths discovered ranged from white-tailed deer to squirrels and included a bobcat and an American mink. Not all the casualties were accidents. The study's authors witnessed drivers intentionally swerving to hit wild animals.

There were patterns of where and when animals encountered vehicles. Run-over wildlife showed up most frequently on paved, two-lane roads. Higher speeds travelled by cars and trucks on paved versus gravel roads mainly contribute to more than doubling the death rate. Four-lane highways may be wide enough to deter animals from crossing, resulting in fewer accidents.

The carnage was also particularly heavy at certain times of the year, especially spring. Peaks in fatalities correspond with when animals are moving about most, such as during mating season or when young disperse. Skunks tend to roam farthest in February and March, right after they finish hibernating. On a 140-mile drive in February 2007, the researchers counted 47 dead skunks.

It's well known that wildlife deaths on roads can be readily reduced with improvements such as underpasses, the study's authors note. They comment that "a society that tolerates such a large number of roadkills places too little value on wildlife." In the United States, with its four million miles of public roads, that number could be huge.


Brenda D. Smith-Patten and Michael A. Patten. 2008. Diversity, Seasonality, and Context of Mammalian Roadkills in the Southern Great Plains. Environmental Management.

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