Behavioral sensitivity to corticosterone in juveniles of the wall lizard, Podarcis muralis

Reptiles exposed to stressful conditions respond with increases in plasma levels of corticosterone (CORT). The outcome of such hormonal fluctuations can affect the organism's physiology and behavior; however, relatively few studies in reptiles have progressed past the effects of stress on the plasma levels of CORT. The purpose of this study was to investigate the effects of CORT on lizard behavior. We focused on activity and thermoregulation of juveniles of the wall lizard, Podarcis muralis. Juveniles with experimentally elevated plasma CORT concentrations showed a higher moving rate and spent a greater amount of time moving. They also spent more time being involved in attempts to escape from a terrarium. This enhanced locomotor activity was associated with significant changes in thermoregulatory behavior, as CORT-increased individuals had reduced thermoregulatory activity than the controls. The same pattern of results was obtained in nature and under laboratory conditions. Thus, CORT levels appear to mediate an important trade-off between locomotor activity and thermoregulation. To our knowledge, this is the first time that the effect of CORT on lizard thermoregulation has been examined.