No evidence of physiological stress in an urban animal: Comparison of fecal cortisol metabolites between urban and rural Eurasian red squirrels

Over the last few decades, urban environments have been regarded as alternative habitats for wildlife. Given the continuous anthropogenic disturbance, however, it remains largely unknown whether urban environments are truly beneficial to some animals or whether the animals are merely just surviving. Glucocorticoids, which play an important role in coping with environmental challenges, are often measured as primary biomarkers of physiological stress. Chronic secretions of these hormones can have deleterious effects on animal health. Some urban stressors are constantly present and may increase the risk of chronic stress. In this study, we compared fecal cortisol metabolite (FCM) levels to evaluate stress levels between an urban and rural population of Eurasian red squirrels Sciurus vulgaris . We hypothesized that if squirrels suffer from greater stress in urban environments, their FCM levels would be significantly higher than that of rural squirrels. Our results showed that FCM levels were not significantly different between the urban and rural squirrel populations, and urban squirrels did not weigh less than rural squirrels. We conclude that the urban squirrels were not subjected to greater stress than their rural counterparts. Urban environments may be preferable for red squirrels, possibly because of release from predators and increased food availability through artificial feeding.