Ecological Correlates of Stress in the Canadian Population of Black-tailed Prairie Dogs

Abstract

Black-tailed prairie dogs (Cynomys ludovicianus) are a foundational species in the mixed-grass prairie ecosystem whose numbers have been declining in Canada over the past two decades. In predator-prey systems, risk of predation has been shown to increase hormones associated with the physiological stress response, and drive population declines by limiting reproductive success. I investigated whether the perceived risk of predation could be a factor contributing to the local decline of this species. Cortisol and corticosterone play a key role in the vertebrate stress response. Therefore, I conducted an experiment to manipulate and track the deposition of these hormones in blood, feces and hair in response to a simulated acute and chronic stressor. I determined that cortisol is the primary hormone in the stress response of this species. My experiment elevated cortisol levels in feces and hair, but a variety of influences precluded clear conclusions about the treatment effect of the experiment. I also investigated how the risk of predation in wild black-tailed prairie dogs is related to cortisol levels and reproductive success. I found that prairie dogs who live on the edge of the colony perceive a higher risk of predation, but this risk does not translate to significant differences in cortisol or reproductive success. Instead, cortisol varies between individuals, but is present at levels that facilitate an adaptive response to environmental challenges, and appears to be repeatable within individuals over time. These results suggest that the risk of predation, whether actual or perceived, should not be considered a limiting factor in the persistence of the Canadian black-tailed prairie dog population.