Author(s): Seth M. Harju
Author(s): Seth M. Harju
Description: White-tailed prairie dog (Cynomys leucurus) populations have declined from historic levels due to poisoning, habitat loss, and introduced disease. Management and conservation of prairie dogs can be aided by investigating the role of steroid hormones in prairie dog ecology, as steroid hormones represent an individual’s behavioral and physiological response to the external environment. To address this issue, I studied the ecology of steroid hormones in free-living and captive white-tailed prairie dogs, by using fecal hormone samples to assess baseline hormone levels over a period of several hours. I quantified the stress response to varying levels of isolation and investigated the origin of age-sex class differences or similarities in steroid hormone levels. To consider possible nonlinear relationships between individual fitness and isolation, I also tested whether prairie dogs experience an Allee effect in steroid hormone levels. Although I did not detect an Allee effect in fecal hormone levels, corticosterone was negatively linearly related to isolation. Twenty percent of corticosterone values were in a distinct outlier tier, possibly caused by a discrete stressful event as an unsuccessful predatory attack. Detection of a statistical difference in hormone levels between age-sex classes may have hampered by high variability and low sample size. Because corticosterone levels were negatively linearly related to isolation, decreases in population density would likely result in increased individual fitness as affected via baseline steroid hormone levels. Even with low sample sizes, the high variation in hormone levels suggests biologically equivalent stress profiles between age-sex classes. With regards to interpreting other research, these results highlighted the importance of correctly choosing and measuring common predictor variables such as population density or age-sex class. Of overriding importance is the discussion of biological significance as well as statistical significance. This can aid in model selection as well as interpreting statistically insignificant results. Future research with prairie dogs would benefit from quantifying the factors contributing to the outlier tier of corticosterone. This study demonstrated methods and obtained results useful to the management and conservation of white-tailed prairie dogs and associated species.