Maximal Metabolic Rates of the Barking Frog (Craugastor augusti)

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The Barking frog (Craugastor augusti, Dugès, 1879) is a direct‐developing anuran from Mexico and the Southwestern US. Very little is known about the metabolic characteristics of this species and maximal metabolic rates of adult animals are unknown. We hypothesized that metabolic characteristics of two genetically distinct populations from TX and NM, inferred from mitochondrial and nuclear DNA (Streicher et al. 2014), might show differences in maximal metabolic rates. We used closed respirometry at 20 °C to measure resting and maximal O2 consumption (VO2max) and CO2 production (VCO2max) to compare adult animals from the two populations, and examined the effects of body mass on metabolism. VO2max was 0.40 ± 0.04 ml O2 g‐1 h‐1 and 0.46 ± 0.02 ml O2 g‐1 h‐1 for the NM and TX populations (mean mass = 46.9 g), respectively, but there was no significant difference. The respiratory exchange ratio (VCO2max/VO2max) for the combined groups was 0.85 ± 0.04 and the aerobic scope (VO2max/VO2rest) was 16.9 ‐ 18.3, indicative of a high aerobic capacity. VO2max and VCO2max were significantly related to body mass (ml O2 h‐1 = 0.47 * Mass + 3.2 & ml CO2 h‐1 = 0.35 * Mass + 3.7). Previous work with anurans (32 species) has shown that VO2max scales with body mass to the 0.97 power (Taigen et al. 1992) and C. augusti falls on the predicted line relating VO2max and body mass for anurans. These results indicate that C. augusti is a highly aerobic species, but genetically distinct populations from TX and NM do not exhibit differences in maximal metabolic rates. Supported by NSF‐IOS 0843082 (MSH) and NSF‐CAREER 0845741(DAC).