Thermal Biology of an Iguanian Lizard, Opiums cuvieri cuvieri, in a Tropical Dry Forest of Madagascar

Abstract

Thermal characteristics of an Iguanian lizard, Opiums cuvieri cuvieri, were examined in a tropical dry forest of northwestern Madagascar. This lizard is an arboreal, strictly diurnal sit-and-wait predator feeding mostly on insects. A field study was conducted from mid-September 1997 to mid-January 1998 and from late-September to mid-November 1998. Ambient air temperature significantly affected body temperature, but sex, snoutvent length, month, perching height, and posture of perching lizards did not show significant effects on body temperature. Effects of time and interaction between ambient temperature and time were significant in the first half of 1997 (dry season) and 1998, but not in the latter half of 1997. Overall body temperature was significantly correlated with ambient temperature, and slopes between them did not significantly deviate from one. However, slopes varied with time of day, and significant correlation between ambient and body temperatures diminished in the midday period. Body temperature was significantly higher than corresponding ambient temperature. In the rainy season, when ambient temperature decreases, the lizards seemed to regulate its body temperature to some extent by selecting hotter microhabitat (the ground). Collectively, although the study site is a relatively open, deciduous forest, where direct solar radiation for thermoregulation by basking is available, O. c. cuvieri exhibits intermediate features between thermoregulator and thermoconformer, having mixed characteristics of both types. © 2004, The Herpetological Society of Japan. All rights reserved.