Seasonal and Intraspecific Variation in Thermoregulation of the Mediterranean Gecko (Hemidactylus turcicus)

The primary objective of this study is to provide the first thorough investigation of thermoregulatory variation in a nocturnal lizard during its activity period. Since comprehensive investigations of thermoregulation have been primarily performed on diurnal lizards, this study addresses the deficit of knowledge about thermoregulation in nocturnal lizards. Thus, the nocturnal gecko, Hemidactylus turcicus , was used to test a protocol proposed by Hertz et al (1993). Measures of body temperatures of field active geckos as well as operative temperatures (the equilibrium body temperatures that animals would attain in given microclimates) were compared to measures of preferred temperatures determined in a laboratory thermal gradient. Measurements were made for four classes of geckos (adult males, adult non-gravid females, adult gravid females, juveniles) in four seasons (June, August, October, March). Field body temperatures and operative temperatures vary between seasons and field body temperatures closely track operative temperatures. In all seasons geckos are ineffective thermoregulators. The constraint of the thermal environment (i.e., low variability in operative temperatures) is advanced as the reason for this seasonal pattern. No seasonal patterns exist in preferred temperatures; however, differences between classes are present. Juveniles have the lowest preferred temperatures and gravid females have the highest preferred temperatures.