Heating and cooling rates in four species of turtles

1. 1. Two basking turtles, Chrysemys picta and Pseudemys scripta, heat significantly faster than they cool. Two terrestrial species, Gopherus polyphemus and Terrapene carolina, cool significantly faster than they heat. 2. 2. Rate of heat exchange in dead basking turtles is the same as the cooling rate in living animals; dead terrestrial turtles have rates of heat exchange similar to their living heating rates. After section of the dorsal roots of the spinal nerves innervating its carapace, Chrysemys rate of heat exchange in both directions is similar to its rate of heating before section. 3. 3. These rates of heating and cooling have been compared with other rates in the literature and equations relating the rate of heat exchange to body weight of reptiles from different habitats have been calculated. 4. 4. We interpret our findings as suggestive of active control of conductance, utilized differently by turtles from two diverse habitats.