Are Highways Stressful for Pikas? Analysis of Stress Hormones of Ochotona princeps Living Adjacent to Interstate 90

Human-modified landscapes disrupt ecosystem connectivity, harming wildlife populations. Some wildlife species live in modified habitats along roads, but their fitness in these stressful environments is poorly understood. Chronic stress alters behavior, reduces reproduction rates, and has been linked to reduced survival. In the Cascade Range of central Washington, American pikas (Ochotona princeps) have colonized anthropogenic rock embankment used for stabilization along Interstate 90 (I-90), but no research to date has determined the fitness or success of this population. To measure basal stress levels of this population, we extracted fecal glucocorticoid metabolites (GCM) from fresh fecal samples. We compared chronic stress levels in pikas adjacent to I-90 with those living in similar rock embankment in a rails-to-trails state park, and in natural talus patches. We also assessed the correlation between fecal GCM concentrations and potential stressors at a subset of sites by measuring environmental temperatures, elevation, and noise levels. A generalized linear mixed model was used to determine differences in GCM concentrations among habitats and assess the potential effects of these environmental variables on stress. Fecal GCM concentrations varied among the 3 habitats. Animals in the I90 habitat had the lowest fecal GCM levels, potentially indicating a suppressed stress response due to their chronic exposure to stressors