Lizards, despite their small size and relatively simple ear structure, have surprisingly good hearing. While their range of hearing frequencies may not be as wide as that of humans, recent research indicates that these creatures can be impacted by noise pollution.
Scientists have studied the effects of low-flying military aircraft noise on an uncommon lizard species, the Colorado checkered whiptail (Aspidoscelis neotesselatus), in a unique collaboration with the US Army.
The Colorado checkered whiptail is considered a “species at risk” by the US Army and a “species of special concern” by Colorado Parks and Wildlife. Native to southeastern Colorado, these lizards inhabit shrubland and mixed grassland along dry creek beds. They are exclusively triploid females that reproduce asexually and are around 30 cm long, including their thin, long tails.
In a study conducted at Fort Carson US military Installation near Colorado Springs, researchers observed several A. neotesselatus populations on the 550 square km of land. With military helicopters and jets frequently flying over their habitat, the researchers set out to examine the effects of such noise disturbance on the lizards’ behavior and well-being.
Led by Megen Kepas, a doctoral student at Utah State University, the team conducted an experimental study in 2021. They coordinated with US army pilots to schedule aircraft flyovers of the designated study area, where noise levels reached up to 112.2 dB – comparable to an orchestra or a power saw.
During the study, the researchers observed and caught unmarked lizards, weighing, measuring, and collecting blood samples for hormone measurements. They also used portable ultrasounds to determine pregnancy status and the number and size of developing eggs. The lizards were then marked according to approved Institutional Animal Care and Use Committee (IACUC) protocols.
Back in the lab, the researchers analyzed the preserved blood samples for concentrations of the stress hormone cortisol, as well as glucose, ketones, and reactive oxygen metabolites (ROMs). While they found that cortisol levels increased sharply immediately after flyovers, glucose, ROMs, and ketone concentrations remained unaffected.
“We found that whiptails at the Fort Carson show a stress response to aircraft flyovers, after we accounted for individual differences in body size and reproductive investment, in particular the number of developing eggs,” said Layne Sermersheim, a master’s student at Utah State University and the study’s co-first author.
The results revealed that the lizards reacted to flyover noise by increasing their blood cortisol and ketone levels, indicating a stress response that rapidly mobilizes more energy resources. Interestingly, females with more developing eggs tended to have a higher increase in cortisol, suggesting that reproductive females may be more susceptible to noise disturbance.
Moreover, the researchers found that the lizards’ behavior was also affected by the noise pollution: they spent less time moving about but more time eating when exposed to noise from flyovers.
“Compensatory eating would allow individuals to maintain their energy levels during a stressful event. This is important because metabolism, physical activity, investment into reproduction, and hormonal responses require energy,” explained Sermersheim.
Overall, the study highlights the physiological and behavioral impacts of noise pollution on the Colorado checkered whiptail lizards. It also underscores their resilience, as the lizards seem to be able to compensate for these disturbances by adjusting their feeding and movement behaviors.
The study is published in the journal Frontiers in Amphibian and Reptile Science.
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.