Lizards exposed to loud noise from overflying helicopters and fighter jets engage in stress eating and spend less time basking in the sun.
Megen Kepas at Utah State University and her colleagues have studied the behaviour of Colorado checkered whiptails (Aspidoscelis neotesselatus) living on Fort Carson US military base near Colorado Springs. Apache, Chinook and Black Hawk helicopters and F16 fighter jets operate from the base, so the researchers wanted to see if they affected the behaviour of the lizards.
To facilitate the study, undertaken in 2021, US army pilots flew over test areas on specified days, and avoided them on others. During flyovers, the sound at ground level peaked at 112.2 decibels – about as loud as a chainsaw a metre away – while maximum levels were otherwise just 55.8 decibels, which is about the level of the buzz of a refrigerator.
The researchers caught a total of 82 lizards, which are considered a species of special concern by Colorado Parks and Wildlife, after observing their behaviour for 3 minutes.
The lizards, which are an all-female species that reproduces asexually, spent less time moving around and more time eating when exposed to aircraft noise. Next, Kepas and her colleagues weighed the reptiles and drew blood for hormone tests. This revealed that levels of the stress hormone cortisol increased after aircraft flyovers.
The researchers suggest that the lizards’ increased stress levels raise energy demands in the body and force them to spend more time eating to compensate. To mitigate the effects, they recommend that the US Army limit the noisiest flyovers.
Richard Griffiths at the University of Kent, UK, says the findings are intriguing, but that it could be useful to observe a control sample of lizards that had never been exposed to aircraft noise.
He says lizards would usually scatter and hide when disturbed. Aircraft noise is probably so ubiquitous on the base that the reptiles there have been “forced to get used to it”, he says.
“If they’re so used to this, if they’ve learned that these noises are not causing a problem in terms of reduced survival, then it’s just reduced to these physiological responses. And then you get this sort of compensatory diversion of behaviour towards eating,” says Griffiths.