Diet: it’s all about location, location, location! How urbanization influences endocrine stress, isotopic signatures, and fecal antioxidants in eastern chipmunks (Tamias striatus)

Abstract

As cities continue to expand on a global scale, animals gain greater access to human food waste, and the consequences associated with the consumption this food waste are poorly understood. Using eastern chipmunks (Tamias striatus) as a study species, I examined the differences in cortisol concentrations and body condition scores, as well isotopic signatures of carbon (∂13C) and nitrogen (∂15N), and fecal antioxidants from eastern chipmunks on an urbanization gradient. I tested the hypotheses that: 1) chipmunks would have lower cortisol levels and better body condition scores if they are living in more urban areas because urban environments may contain higher amounts of human food waste relative to natural habitats, and 2) chipmunks would have higher carbon and nitrogen signatures and excrete more antioxidants in more urban environments compared to their natural counterparts because they may be consuming human food waste. Chipmunks were sampled across Sudbury, Ontario from 20 areas with varying levels of urbanization. Each time a chipmunk was captured, hair samples, fecal samples, and body measurements were collected. To quantify urbanization, I surveyed all study sites over a three-day period to score the level of human activity. I found that cortisol significantly differed among chipmunks across the gradient, such that chipmunks in more urban habitats experienced the highest levels of cortisol. I found chipmunks and poorer body condition in the most urban areas. Chipmunks in more urban habitats produced a higher nitrogen signature than their natural counterparts, while no significant difference was observed in carbon or fecal antioxidants. My results help us to understand differences in diet across as well as the physiological changes associated with urban habitats, which may help us understand how other species may respond to urbanization