Null models and the thermal biology of the anguid lizard Anguis fragilis; evidence for thermoregulation?

Abstract

Observations were made on the behaviour and body temperatures of the legless lizard Anguis fragilis when active above ground in outdoor enclosures. The lizards were most frequently observed in partially shaded locations followed by fully shaded areas; full basking and locomotory movement were minor activities irrespective of weather conditions. Weather conditions had no significant influence on behaviour. Tests for thermoregulation using null models indicated that the main reason for movement above ground was thermoregulatory. Body temperatures were significantly higher than shade operative temperatures but lower than operative temperatures in open locations whatever the weather. Standard deviations in body temperature, employed as a measure of thermoregulatory precision, were lower than standard deviations of operative temperatures in sunny weather but not significantly different from operative temperatures during overcast weather or shaded operative temperatures during sunny weather. The limited amount of locomotory movement suggests thermoregulation was achieved through selection of appropriate microenvironments. © Koninklijke Bill NV 2005.