Temperature and Energy Characteristics of the Sagebrush Lizard (Sceloporus graciosus) in Yellowstone National Park

Abstract

The mean cloacal temperature for 41 Sceloporus graciosus in the field was 30.9*C. Both the mean air temperature one inch above the ground (23.7*C) and the mean substratum temperature (25.7*C) were significantly lower than the mean cloacal temperature. The mean cloacal temperatures of discrete spring, summer, and fall samples of lizards collected in 1966 measured in a laboratory temperature gradient (N = 58, 70 and 60 respectively), differed significantly from each other, with the spring sample having the lowest mean (28.9*C) and the summer sample the highest (32.3*C). The mean critical thermal maximum of a sample of 14 lizards collected August 1965, was significantly higher than the mean critical thermal maximum of a sample of 10 lizards collected in June 1966 (43.6 vs 42.6*C). While the mean critical thermal maxima of three samples collected in 1966 were not significantly different from each other, they, as well as the mean temperatures obtained from the samples in the thermal gradient, followed the general seasonal trend in temperatures. Oxygen consumption measured at 30*C with a Warburg apparatus was approximately 30% of the value indicated for most species of lizards. Mean fat storage on 7 September 1966, was approximately 23% of the total dry body weight for both juvenile and older lizards. Using estimates from oxygen consumption and fat loss, an adult lizard produces 2000-2800 cal during a hibernation period of 220 days.