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Thermal dependence of locomotory energetics and aerobic capacity of the Gila monster (Heloderma suspectum)

1983; Springer Science+Business Media; Volume: 151; Issue: 2 Linguagem: Inglês

10.1007/bf00689909

1432-136X

Henry B. John‐Alder, Charles H. Lowe, Albert F. Bennett,

Amphibian and Reptile Biology

The thermal dependencies of sustainable locomotion and aerobic energetics were determined in the Gila monster, a lizard of relatively low thermal preference. Maximal aerobic speed (MAS) is 0.70 km/h at 25°C and 1.03 km/h at 35°C (Q10=1.5). Endurance declines as speed is increased above MAS, and Gila monsters are unusual in being unable to engage in brief periods of high-speed burst locomotion. The rate of O2 consumption ( $$\dot V_{O_2 } $$ ) during locomotion has the same thermal dependence as that of MAS. Maximal $$\dot V_{O_2 } $$ 's are 0.594 ml O2/(g·h) at 25°C and 0.896 ml O2/(g·h) at 35°C (Q10=1.5). The masscorrected $$\dot V_{O_2 } $$ max of the Gila monsters is highest among lizards at 25°C and is relatively high, consistent with other platynotans, among lizards at 35°C. Net cost of locomotion is temperature independent and is relatively low among lizards. Low net cost of locomotion together with high $$\dot V_{O_2 } $$ max's lead to Gila monsters having high MAS's at both 25°C and 35°C. Gila monsters thus appear to be well adapted for aerobic, sustainable activity. The total cost of locomotion shows a positive thermal dependence. However, the minimum cost of transport, attained at the highest sustainable speed, is temperature independent. Locomotion at MAS becomes faster with increasing body temperature with no obligatory increase in total cost of locomotion.