Urban Noise as a Stressor in Side-Blotched Lizards

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Marilize Van der Walt, Utah State University

Life Sciences

Urbanization is accompanied by a lot of changes to the landscape that have the potential to affect the native species inhabiting the area. If animals are chronically exposed to these anthropogenic disturbances and are unable to acclimatize, changes in circulating glucocorticoid hormones may cause adverse effects to the animal’s health, such as an impairment in innate immune activity. One such disturbance is human-induced noise. Using the side-blotched lizard, Uta stansburiana, because of their localized habitat and inability to escape such disturbances within the urban environment, we looked at the field and lab components of noise as a stressor. We first measured decibel levels in urban and rural field sites in their natural habitats in St. George, Utah, and conducted a lab study exposing U. stansburiana to either a synthesized urban sound recording or no sound recording (control) for nine days. We collected blood samples and measured circulating corticosterone and testosterone concentrations and bactericidal ability to determine if there are endocrine and immune alterations in response to increased noise decibels. Our results show that lizards exposed to urban noise experienced increased corticosterone levels indicative of stress. Furthermore, bactericidal ability was indirectly affected by noise through significant correlations between body condition and corticosterone and testosterone concentrations. These results indicate that an increase in ambient decibel levels acts as a stressor to animals in urban areas. By dissecting out an individual component of a complex stressor we can better understand the effects of urbanization as a whole.