Summary: LOW COST OF LOCOMOTION PERMITS ACTIVITY AT LOW TEMPERATURES IN A
NOCTURNAL LIZARD. K. Autumn*, R.B. Weinstein, and R.J. Full. University of Cali-
Thermal optima for physiological processes are generally high (3540_C) in lizards. Performance
decreases substantially at low temperatures, yet some nocturnal lizards are active with body tem-
peratures below 15_C. Nocturnal lizards may have derived features that permit activity at low tem-
peratures. Teratoscincus przewalskii, a nocturnal, terrestrial gecko from Northwestern China (11
g), was able to sustain exercise at 15_C on a treadmill for over 60 min at 0.18 km_h1. Resting and
maximum oxygen consumption at 15_C and 25_C were similar to predicted values for diurnal liz-
ards, supporting the hypothesis that much of thermal physiology in lizards is evolutionarily static.
The minimum cost of transport (Cmin, 0.73 mlO2 kg1m1) for T. przewalskii was 1/3 of the pre-
dicted value for an 11 g lizard. This low cost yielded a maximum aerobic speed (MAS) of 0.27
at 15_C. If Cmin in T. przewalskii was typical for a lizard, the MAS would be 1/3 this value
. Field observations indicate that individuals of T. przewalskii move at an average
speed of approximately 0.2 km_h1
. Field body temperatures during activity averaged 15.3_C. We
propose that low Cmin is an aptation that permits nocturnality in T. przewalskii.