These Lizards Stress-Eat When Loud Military Aircraft Fly Overhead

Colorado checkered whiptails on a U.S. Army base show increased stress levels and altered behavior after noisy jets and helicopters pass by, a study finds

a yellow and black striped and checkered lizard on the ground
A Colorado checkered whiptail Ken Holtgrewe via Getty Images

To a Colorado checkered whiptail lizard, the roaring sound of a military jet flying overhead can cause some serious stress. A new study suggests the four-inch-long reptiles have found a way to cope with the anxiety: They’re stress eating. 

On a normal day for the lizards living on the U.S. Army Fort Carson Military Base in Colorado Springs, the ambient noise level is no louder than that of a humming refrigerator. But on flight days, the sound of jets and helicopters can reach up to 112 decibels, which is akin to hearing a car horn from three feet away—and it’s enough to put the lizards on edge.

To find out how these reptiles are impacted by low-flying aircraft, scientists observed their behavior for three minutes following a flyover, then they caught the lizards to perform blood tests.

After aircrafts passed, the lizards’ levels of cortisol, a hormone linked to stress, had skyrocketed, the team reports in a paper published last week in the journal Frontiers in Amphibian and Reptile Science. Their behavior also shifted—the lizards moved around less and ate more in a likely attempt to rebuild the energy resources lost during their stress reaction.

“Here we show that noise disturbance does have measurable physiological impacts on Colorado checkered whiptails,” says first author Megen Kepas, a biologist at Utah State University, in a statement. “We also show that they are somewhat resilient and may compensate for this to some degree by altering their feeding and movement behaviors.”

Colorado checkered whiptails are an all-female species that reproduces asexually. The striped reptiles live along dry creek beds in the shrublands and grasslands of southeastern Colorado. But because of habitat loss, they are now considered a “species of special concern” by Colorado Parks and Wildlife and “at risk” by the U.S. Army. Studying the lizards’ reaction to noise pollution provides scientists with a clearer picture of the threats they face.

The researchers tested the lizards during their breeding season in 2021. Scientists asked pilots to, on certain days, fly over the test areas in the 212-square-mile property of the Fort Carson base, which was the main funder of the study. On other days, the test areas were left undisturbed.

In all, the team ended up with blood samples from 82 females, with no lizard captured more than once. Each lizard was weighed and measured, and all individuals underwent blood tests for stress hormones as well as ultrasounds to see if they were pregnant. Females carrying more eggs had more dramatic increases in cortisol, per the statement.

“I found the study to be super interesting,” Tracy Langkilde, a biologist at Pennsylvania State University who was not involved with the paper, tells CNN’s Mindy Weisberger. Much of the research on the impacts of sound pollution is focused on birds, she tells the publication, so this study provides a new perspective.

Still, the researchers could have used a control group of lizards that had never been exposed to military flyovers before, to compare how they react to the jets, Richard Griffiths, a biologist at the University of Kent in England who was not involved in the study, tells New Scientist’s Matthew Sparkes. The females that live near the base have probably been “forced to get used to it,” he says to the publication.

Because stress could impact the Colorado checkered whiptail’s behavior, the scientists recommend that military flyovers are limited over highly populated lizard habitats during their reproductive season. They write that the altitude of the flights should be increased, which would limit the stress-inducing noise on the ground. Ideally, the sound should be below 50 decibels, per the paper, keeping the lizards’ surroundings no louder than the standard level of a refrigerator hum.

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