Thermoregulation in Nocturnal Ecthotherms: Seasonal and Intraspecific Variation in the Mediterranean Gecko (Hemidactylus turcicus)

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Journal of Herpetology






Comprehensive investigations of thermoregulation have been primarily performed on diurnal lizards. The nocturnal gecko, Hemidactylus turcicus, was used to test a protocol proposed by P. E. Hertz, R. B. Huey, and R. D. Stevenson in 1993. Measures of body temperatures of field active geckos (Tb) and operative temperatures (Te), the equilibrium body temperatures that animals would attain in given microclimates, were compared to measures of preferred temperatures (Tp) determined in a thermal gradient. Measurements were made on adult males, adult nongravid females, adult gravid females, and juvenile geckos in four seasons (June, August, October, March). Both Tb and Te varied between seasons; however, Tb closely tracked Te. No seasonal patterns existed in Tp; however, juveniles had the lowest Tp, whereas gravid females had the highest. Regardless, in all seasons geckos were ineffective thermoregulators. The low variability in Te is the likely cause for this pattern. For such “thermoconforming” species, we suggest that the magnitude of the variation in Tb, Te, and Tp be included in assessments of how well organisms regulate to their set-point (preferred), temperatures. We conclude that geckos, and possibly many nocturnal ectotherms, thermoregulate during the day when a more variable thermal environment exists.