Thermoregulation as a function of thermal quality in a northern population of painted turtles, Chrysemys picta

• Published in: Canadian journal of zoology Vol. 85; no. 4; pp. 526 - 535
• Main Authors: Edwards, A.L, Blouin-Demers, G
• Format: Journal Article
• Language: English
• Published: Ottawa, ON National Research Council of Canada 01.04.2007; NRC Research Press; Canadian Science Publishing NRC Research Press
• Subjects: Biological and medical sciences; Body temperature; Chrysemys picta; Distribution; Engineering research; Environmental aspects; Field study; Freshwater; Fundamental and applied biological sciences. Psychology; Habitat selection; Habitats; Heart rate; Ocean temperature; Population; Predators; Regulation; Temperature; Thermoregulation. Hibernation. Estivation. Ecophysiology and environmental effects; Turtles; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Canada; Chrysemys picta; Vertebrata; Chelonia; Energetic cost; Seasonal variation; Body temperature; Thermoregulation; Reptilia
• ISSN: 0008-4301; 1480-3283; 1480-3283; 0008-4301
• DOI: 10.1139/Z07-037

Body temperature affects nearly all processes of ectotherms. Reptiles do not generate sufficient body heat to regulate their body temperature internally and therefore use behavioural thermoregulation. We determined whether thermoregulatory effort varied among seasons in an environment where large temporal differences in environmental temperatures (T e ) exist. We took 31 297 internal body temperature (T b ) measurements from 18 painted turtles ( Chrysemys picta (Schneider, 1783)) throughout their active season. We estimated T e with physical models and water temperatures. We measured the range of preferred body temperatures (T set ) in a thermal gradient. T set was 21.3-25.0 °C. We used T b , T e , and T set to calculate standard thermoregulation indices (E x and d e - d b ). An E x of 40.7% and a d e - d b of 2.4 °C indicated that painted turtles are moderate thermoregulators, despite inhabiting a high-cost environment. Effort to regulate T b increased as the thermal quality of the habitat decreased. Thermoregulatory effort was higher when T set could not be achieved. Painted turtles put more effort in thermoregulation in the early season than in the rest of the season. This within-species pattern follows the pattern seen among species. This study is the first to measure T b internally and to apply standard thermoregulation indices to free-ranging turtles.