The Thermal Dependence of Locomotion, Tongue Flicking, Digestion, and Oxygen Consumption in the Wandering Garter Snake

Abstract

The body temperature (Tb) of garter snakes (Thamnophis elegans) can vary considerably in the course of a day (e.g., 4-33 C), and information on how Tb affects physiological and behavioral processes is required to evaluate the significance of that variation. We measured crawling speed, swimming speed, tongue-flicking rate, digestive rate, and oxygen consumption at Tb's of 5-35 C in snakes collected in eastern Washington and acclimated to September field photoperiod and temperature cycles. All functions were strongly dependent on Tb. The maximum speed of crawling (X̄ = 0.74 m s−1) occurred at Tb = 34.5 C; that of swimming (X̄ = 0.69 m s−1) occurred at Tb = 28.5. At < 30 C, the snakes crawled more slowly than they swam, but the reverse was true at higher Tb. At Tb = 30 C, the snakes moved their tongues up and down at a maximum rate of 22 Hz. Digestion rate increased sharply above 20 C, to a maximum of 0.45 mice/day within the Tb range of 25-35 C. All snakes regurgitated their meal at 10 C. The Q10 values for mass-specific oxygen consumption over the 5-15, 15-25, and 25-35 C Tb ranges were 2.4, 1.3, and 5.0, respectively. Among the performances studied, swimming speed was the least sensitive, and digestion rate the most sensitive, to Tb. FieldTb data indicate that all functions would be near maximum levels during the day but would be significantly reduced at night. We conclude that no single Tb is best for the ecological tasks of prey capture, predator avoidance, and energy conservation.