Severed Chicken Head Experiment Shows We're Underestimating How Many Animals Are Killed by Cars

The shocking experience of hitting a deer on the road is occasionally followed by something you might find even stranger—passing pickup truck drivers asking if they can keep the corpse. 

But it shouldn’t come as a surprise that non-human scavengers pick up roadkill, too. Researchers in the United Kingdom who study these critters think that their roadside eating habits have led humans to seriously underestimate how many animals are killed by cars.

“Roadkill disappears very quickly,” Sarah Perkins, study author from Cardiff University in Wales, told Gizmodo. “Our actual estimate of the number of animals killed on the road is much higher than before.”

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The researchers set up camera traps in the city of Cardiff, with chicken heads to serve as the faux-roadkill bait. Animals removed three quarters of the chicken heads within the 12 hours. But if the heads were placed on the road at 9 a.m., 60 percent of the heads were gone within two hours. Given this data, the researchers think that the actual number of animals killed on the road could be up to six times greater than estimates, according to the study published in the Journal of Urban Ecology.

And that’s important, because the impact of traffic on wildlife is a crucial question to ecologists, Fraser Shilling, co-director of the Road Ecology Center at the University of California, Davis, told Gizmodo. Studies like Perkins’ will help scientists understand how to better estimate roadkill and who is picking the carcasses up.

This study has its limits, Shilling said. Estimating the population size and reproduction rate of species killed on the road still remains a challenge. Perkins pointed out that chicken heads are smaller than the animal most commonly killed on the road in the UK, badgers, but could perhaps stand in as a proxy for smaller animals like mice and birds. She thought the study’s conclusions would definitely apply to the United States as well, but said more work needs to be done studying roads in less urban areas.

If you were wondering, humans were not on the list of scavengers included in the most recent studies, but they have picked up fake roadkill used in older studies, Perkins said. Several domestic dogs took the chicken heads, too.

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But we have to be thankful for the foxes, gulls, and other scavengers who are removing the mess, said Perkins. “Some of our species are probably providing an ecosystem service. Some things otherwise might not be so pleasant for people—our wildlife is cleaning that up.”

[Journal of Urban Ecology]

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Former Gizmodo physics writer and founder of Birdmodo, now a science communicator specializing in quantum computing and birds

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DISCUSSION

But aren’t the smaller animals like mice less likely to be killed on the road? For them, only the tires are dangerous, while larger animals have to fear the entire width of the car. They also move fast, compared to a wadling skunk, so probably spend less time on the road when they cross it.