No Difference in Corticosterone Concentrations Between Missouri Three-Toed Box Turtles Living in an Urban and a Rural Site

Baseline health data for species of conservation concern are important for understanding threats to the long-term viability of populations. One indication of health is physiological stress among individuals. Corticosterone (CORT) is frequently used to quantify stress in free-living reptile populations, as high values may be associated with reduced fitness. Herein, we describe and validate methods for quantifying blood CORT levels in three-toed box turtles (Terrapene mexicana triunguis). We subsequently use this information to evaluate stress levels in 2 populations of free-living three-toed box turtles in Missouri, USA. To our knowledge, this is the first quantification of CORT levels in the three-toed box turtle. In 2012 we collected blood samples from 11 three-toed box turtles in human care at the Saint Louis Zoological Park (zoo), St. Louis, Missouri for assay validation, and from 2012 to 2016 we collected 220 samples from 144 free-living three-toed box turtles at 2 sites, 1 urban and 1 rural. In the zoo turtles, mean CORT concentration was 0.71 ± 0.10 ng/mL. Following a handling experiment, CORT concentration increased to 3.14 ± 0.72 ng/mL (P = 0.011). Mean CORT levels between free-living turtles at the urban and rural sites did not differ (urban = 0.54 ± 0.08 ng/mL, rural = 0.37 ± 0.02 ng/mL, F pr = 0.12). Sex did not influence CORT levels (F pr = 0.29). These results suggest that the turtles living in the urban environment did not experience chronic elevated glucocorticoid production and supports urban parks as potential habitat for box turtles