Voluntary Hypothermia in Reptiles

Studies on lizards in laboratory thermal gradients which are not shut down at night reveal complex thermoregulatory behavior. Maintenance of the high, characteristic levels of body temperature known for active lizards may be abandoned. Low levels, which incapacitate the lizards, are selected. Evidence of complex responses of the "thermostat" at a reptilian level of organization suggests a reassessment of our theories concerning the evolutionary status of "torpidity" in birds and mammals.