Operation roadkill

Joshua Tewksbury (left) hangs off the back of his truck as it rumbles from one field site to the next in southern Bolivia. At night, the team will be scanning these same roads for nightjars. Credit: Courtesy of Brendan Borrell Ecologist Joshua Tewksbury and h

By | December 1, 2007

<figcaption>Joshua Tewksbury (left) hangs off the back of his truck as it rumbles from one field site to the next in southern Bolivia. At night, the team will be scanning these same roads for nightjars. Credit: Courtesy of Brendan Borrell</figcaption>
Joshua Tewksbury (left) hangs off the back of his truck as it rumbles from one field site to the next in southern Bolivia. At night, the team will be scanning these same roads for nightjars. Credit: Courtesy of Brendan Borrell

Ecologist Joshua Tewksbury and his team from the University of Washington in Seattle were rumbling along a road in southern Bolivia one night last spring with a truck full of plant samples, when a pair of yellow eyes materialized in the middle of the track. It was a Nyctidromus albicollis, also known as a nightjar, a medium-sized nocturnal bird with long wings, short legs, and a squat head. In Tewksbury's experience, nightjars are wise enough to fly away from approaching vehicles. But this one refused to budge. The truck made no attempt to stop, and the bird vanished underneath. That was that. Like Schrödinger's cat, it was unclear whether the bird was alive or dead, but judging by the engine's giggles and gasps, the team assumed the worst.

According to one dubious extrapolation by Merritt Clifton, editor of the Animal People Newspaper, 41 million skunks, 26 million cats, and millions of other species are killed by cars each year in the United States. Clifton's estimate is based on the Roadkill Project, a survey conducted by schoolchildren in New England, so it is unclear whether their limited counts are representative of the entire country. Still, had Charles Darwin known about roadkill, he might have wondered why these critters are not adapting.

That spring night in Bolivia, Tewksbury (who was slightly delirious from the day's botanical fieldwork, studying wild chili peppers), realized that if any animal has evolved a roadside manner, so to speak, it would be the nightjar. For most of their evolutionary history, nightjars lay in wait for flying insects where they emerge from dense forests, typically at the edge of clearings. In modern times, they have taken to the roads. "The general hypothesis is that nightjars on main roads know how to deal with cars," says Tewksbury. "Nightjars on back roads don't, simply because there are so few cars; there's no selection for dealing with cars."

Thus, an experiment was born. Or, at least, a pilot study. After all, what else can a team of data-hungry biologists do when they're cooped up in a car six hours a day, shuffling between remote research sites? Tewksbury could watch for yellow eyes. Carlos Manchego, a field assistant, could hang outside the vehicle and estimate the survival rate. The task of data recording is delegated to me, a journalist and the only member of the expedition who still has a field notebook out at midnight. Tewksbury preps me: Nightjars that did not easily get out of the way were considered to fly "inappropriately."

After the methodology is worked out, complications arise. "How many nightjars have we had so far?" Tewksbury asks.

"I have to check the notes," I say. "We're at four: one flier, three nonfliers."

"The first one flew, other three didn't," Tewksbury says.

"Second one, we may have killed," says graduate student Noelle Machnicki.

"So that wasn't appropriate," he responds, in reference to the bird's faulty attempt to avoid the truck.

"Third one, we may have killed. No, no, Carlos saw it," she says.

"Still, wasn't appropriate," Tewksbury says.

"And the last one we had to brake for," she says.

"That's a good one, too," he says, because it lent further support to his theory.

"We should tell Uco [the driver] to maintain his speed," says Machnicki.

"No, we'd kill too many nightjars," says Tewksbury.

"If he has to brake, then that's a nonflier: inappropriate," she says.

"Let's do 'fly,' 'not-fly,' and 'edge,' 'center.' That's all we really need to do," instructs Tewksbury.

Thirty-five kilometers later, the team still sorely lacks in the data department, but they are already musing over publication. "We'll submit it to Science," says Machnicki. Tewksbury chuckles and says that probably wouldn't fly, "but it still might be a note to The Auk or something."


December 5, 2007

I was not amused. Do we really want automobiles to select those species able to survive? Could the scientists have used the hours and their combined brain power to design better ways to collect data so the extent of the problem could be known? Identify factors making different species more or less susceptible? Think up ways to prevent roadkills?
Avatar of: anonymous poster

anonymous poster

Posts: 39

December 8, 2007

I loved this article. This is an interesting area of nature/man relations that has been seriously understudied. We have a great deal of info on carbon dioxide emission, hunting, etc. but almost nothing on cars.\n\nWhat creatures adapt to cars, which don't? Is this natural selection, or behavioral selection. That is, do these animals have to see cars to develope strategies or is this something that will be implanted into their genes?\n\nAre these animals adapting by getting flashier, so cars brake, or by getting faster, or by getting smarter? Absolutely fascinating. \n\nEven if this is a little cruel of an experiment (but, these animals would be killed wether or not the scientists recorded it, right?) there are surely productive things to be learned. Do animals run from noisy cars, or quiet ones? Do they get out of the way of bright headlights, or dimmer ones? Are their noises that can scare the animals out of harms way? Without knoledge, we are lost, and so are the roadkill.\n\n Someday all new areas of research will go into building man's dream car. If sufficiently scientific and informative research pops up, they will consider putting the longevity of critters in mind.
Avatar of: Merritt Clifton

Merritt Clifton

Posts: 1

December 19, 2007

It is axiomatic in news reporting that a good reporter verifies information before putting it into print. In this case, your reporter apparently made no effort to verify factual claims attributed to me before publishing them and then calling them "dubious." \n\n Indeed they are dubious, because those numbers do not come from my data, and 41 million skunks and 26 million cats would have been approximately the total skunk and feral cat populations of the United States at the time I did my research on roadkill frequency, in 1992-1998. \n\n The Dr. Splatt roadkill data collected mainly in the Northeast projected that as many as 9 million skunks per year and 5 million cats per year were being roadkilled as of 1993-1994, when I published a table of projected findings under the headline "Cold winter holds down roadkill; peaks coincide with moon phases," in the ANIMAL PEOPLE edition of September 1994. However, while I believed that the cat project probably would hold up, because cats are found proportionate to human population all over the U.S., I pointed out that the skunk projection included a huge amount of regional distortion.\n\n Later I used the much more rigorously compiled Strah Poll, a roadkill count kept for the past 15 years by Cathy Strah, of Mentor, Ohio, and found that while skunks are disproportionately likely to be hit, they are not hit in anything like the numbers that the Dr. Splatt data suggested.\n\n Roadkills of cats have meanwhile fallen like a rock, between the greater tendency of cat owners to keep their cats indoors and the steep reduction in the U.S. feral cat population achieved during the past 15 years by the advent of the neuter/return population control technique. \n\n The U.S. feral cat population was about 20 million in 1937, 30 million in 1950, and peaked at 40 million circa 1991, according to early studies by John Marbanks and my own more recent work. The 40 million was a midsummer peak-of-kitten-season high. 26 million was the year-round average, and only five years later, 26 million appeared to by the summer peak. Since then, the summer peak has fallen to about 12.5 million, with a mid-winter low of just over 6 million, for a year-round average of about 9.3 million.\n\n I would guess that roadkills of cats have fallen proportionately--although owned cats are more likely to be hit, simply because there are more of them at large. The best available data indicates that about half of all cat owners allow their cats to go outdoors, but they have only about a third of the owned cats, owing to the much higher mortality of cats who go outside. Thus about 30 million owned cats roam.\n\n If there were five million roadkilled cats per year at a time when there were about 50 million owned and feral cats at large, then by crude extrapolation there might be as many as 3.9 million cats roadkilled today. But I think this projection would probably be about four times too high, partly because coyotes have taken much of the urban habitat that 15 years ago was occupied by feral cats, and coyotes appear to have overtaken the car as the second most active cat predator. Animal control captures are still in first place, however, currently accounting for about two million feral cat deaths per year (down by 75% from circa 1994, but still high relative to all other known causes of death.\n\nMerritt Clifton\nEditor, ANIMAL PEOPLE\nP.O. Box 960\nClinton, WA 98236\n\nTelephone: 360-579-2505\nFax: 360-579-2575\nE-mail: anmlpepl@whidbey.com\nWeb: www.animalpeoplenews.org
Avatar of: Brendan Borrell

Brendan Borrell

Posts: 1

December 23, 2007

I appreciate Mr. Clifton's correction of the "dubious" figures I had attributed to him. Curiously, I obtained that factoid from the website of the Roadkill Project, which also supplied the data upon which Clifton's extrapolation is based.

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