Maximum and resting rates of oxygen consumption and heart beat were measured over a range of body temperatures for three species of lizards. These are Egernia cunninghami and Tiliqua rugosa (Scincidae) and Physignathus lesueuri (Agamidae). Maximum oxygen consumption rate was also measured for Amphibolurus barbatus (Agamidae). Aerobic scope, the difference between maximum and resting rates of oxygen consumption, is maximal near the preferred body temperature (PBT) of each species. For three of these species where body temperature data exist, ca. 85% of maximum aerobic scope may be attained in the body temperature range of animals found active in the field. Heart rate increment, the difference between resting and maximum heart rates, is maximal 2 to 4 C above the PBT. Oxygen pulse, the volume of oxygen consumed per heart beat, is independent of body temperature in resting lizards, but is inversely related to body temperature in active lizards. The relationship of aerobic scope and body temperature in reptiles has been reconsidered. All data are consistent with the hypothesis that maximum aerobic scope occurs near the PBT in non-varanid thermophilic lizards.
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