Operative Environmental Temperatures and Basking Behavior of the Turtle Pseudemys Scripta

Abstract

Operative environmental temperatures (Te, an index of the thermal environment) were measured for basking Pseudemys scripta in South Carolina. Operative environmental temperatures were good predictors of the basking behavior of P. scripta. Turtles in this study generally did not bask unless Te was 28°C (preferred body temperature) or higher. This demonstrated that basking was not a random behavior in respect to Te, and implicated thermoregulation as a major factor eliciting basking behavior. Operative environmental temperature was positively related to short—wave and total solar radition as well as to air and substrate temperature. Substrate temperature was the best single predictor of Te. A multiple regression equation (Te = 0.005R + 0.103Ta — 1.16 log V + 0.932Ts — 2.54, r2 = .90, where R = total radiation in watts per square metre, Ta = air temperature in degrees Celsius, V = wind speed in metres per second, and Ts = substrate temperature in degrees Celsius) defines the relationship of Te to microclimate variables. Movement of the sun through the day results in spatial variation in Te's available to turtles and influences their location and basking behavior.