We carried out experiments in outdoor enclosures with a substrate
of uniformlow grass. Trials were performed on sunny days, at an ambient
temperature of approximately 25 °C. We tested each subject turtle
at three different temperatures (15 °C, 20 °C and its species-specific
Tset), once at each temperature. Tset was estimated as the upper set
point temperature (USP) selected by turtles in a basking device (see
below). The Tb atwhich turtles cease basking and shift towater properly
represents the upper bound of Tset and can be precisely determined. For
this reason, it can be considered an appropriatemeasure of Tset associated
with maximizing processes in which performance increases continuously
to To and then sharply decreases [9,36–39]. Thus, we
considered the USP of basking as an appropriate measure of Tset that
should maximize righting performance in turtles under the coadaptation
hypothesis.