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Behavioral and Physiological Responses of Ornate Box Turtles (Terrapene ornata ornata) to Temperature Stress
Temperature is a critical regulator of physiological and behavioral processes. When body temperature departs from a preferred body temperature range there can be consequences to performance and survival. Therefore, extreme temperatures may initiate physiological responses and intensify trade-offs between key fitness functions such as foraging or predator avoidance. I explored the behavioral and physiological responses that ornate box turtles ( Terrapene ornata ornata), have to stressful environmental temperatures. First, I exposed adult female turtles to a range of temperatures which included 38°C, 28°C, 21°C, and 4°C and measured glucocorticoid hormone concentrations as an indicator of stress. I found that exposure to temperature extremes led to higher glucocorticoid concentrations. Second, I examined turtle thermoregulatory behavior (cover use) by comparing turtles with and without additional shade in an outdoor enclosure. I found that additional shade did not affect cover use, but that turtles with no shade had significantly warmer carapace temperatures and tended to lose more mass. I then challenged turtles with food limitation to see if thermoregulatory behavior and cover use would be altered. Although food limited turtles showed physiological signs of fasting (mass loss along with lower glucose and higher ketone body concentrations), they did not alter thermoregulatory behaviors or show increased glucocorticoid levels. Due to increased predation risks for small juvenile turtles, thermoregulatory decisions could differ between juveniles and adults. In separate studies, I investigated the responses of juvenile turtles when faced with a trade-off between thermoregulation and using a refuge. I found that juveniles were more likely to use a shelter even if shelter use resulted in body temperatures below preferred. These studies also indicated that larger juveniles were more willing to leave a refuge to thermoregulate. Together, these studies suggest that temperature is an important factor determining ornate box turtle behavior when faced with trade-offs, but the importance of temperature may diminish when more threatening stressors (predation) are present.^
Neyer, Abigail A, "Behavioral and Physiological Responses of Ornate Box Turtles (Terrapene ornata ornata) to Temperature Stress" (2018). ETD collection for University of Nebraska - Lincoln. AAI10841801.