DAILY BODY-TEMPERATURE VARIATION IN FREE-RANGING RUBBER BOAS

A current generalization regarding body temperature (T-b) variation in free-ranging reptiles is that, when possible, they maintain relativel y high T-b's to optimize important biological functions. However, beca use this generalization is based primarily on studies using opportunis tic spot measurements of diurnal lizards, it is both phylogenetically and ecologically biased in addition to underrepresenting inactive anim als. We addressed these problems by continually monitoring T-b variati on in free-ranging rubber boas (Charina bottae), a nocturnal bold. We surgically implanted temperature sensitive radiotransmitters into 14 f emale snakes and monitored their T-b's at 5-min intervals for periods of up to a year (September 1990 to September 1992) using an automated monitoring system. Operative environmental temperatures (T-e's) were c oncurrently measured using physical snake models. We describe four dai ly T-b patterns, including a preciously undescribed pattern in which s nakes were nocturnally active, frequently at unusually low temperature s (modal activity temperature = 14 C). Nocturnal activity occurred abo ut once every eight days. As found in previous studies, pregnant snake s maintained higher and less variable T-b's than nonpregnant snakes, w hich is likely important for maintaining a high developmental rate. Ou r results also support findings from another study in which the therma l environment prevented snakes from maintaining high, stable T-b's muc h of the time. However, unlike precious studies, we found th;it when u nconstrained by the thermal environment, snakes did not maintain high stable T-b's much of the time. These results raise questions regarding the predictability of reptilian thermoregulation using environmental temperatures.