Big City Blues: The effects of urbanization on Western Fence Lizard (Sceloporus occidentalis) stress and response to competitors
Urquidi, Emily R.
Putman, Breanna J.
Department of Biology
California State University
San Bernardino, California USA
As urbanization increases, animals are subjected to new stressors caused by human activity, including habitat fragmentation. Habitat fragmentation forces animals to reside in small habitat patches. In these small patches, the possibility of urban lizards encountering a competitor may increase. Although urban areas have been found to have lower biodiversity, invasive species are commonly introduced to urban areas. Considering this, we predict that lizards in urban areas will be more stressed than their natural counterparts. We also believe lizards in urban areas may be more experienced with conspecific competition, but less experienced with heterospecific competition. Thus, we predict that lizards in urban areas will have higher baseline CORT concentrations and higher stress-induced CORT concentrations after encountering competitors compared to natural lizards. To study this, we compared the baseline CORT concentrations from 69 Western Fence Lizards (Sceloporus occidentalis) caught at two replicate urban and natural sites located in two different areas of Southern California: San Bernardino and Claremont. One sample was taken from an urban population, which consists of relatively high human population densities and high levels of impervious surface; we collected another sample from a natural population, which consists of mostly intact sage scrub habitat. To quantify stress response to competitors, we ran behavioral trails pairing Western Fence Lizards with either a conspecific or novel heterospecific competitor. After the trial finished, we took a blood sample in order to quantify stress. Our results show that lizards in urban areas have higher baseline CORT. Although we did not find a difference between population stress-induced CORT levels when subjected to a competitor, we did find that lizards were the most stressed after a conspecific trial.