Ecological Study of Oxygen Consumption in Three Species of Rattlesnake, Crotalus atrox, C.lepidus and C. molossus (VIPERIDAE) from the Northern Chihuahuan Desert

The purpose of this study was to compare oxygen consumption of three species of rattlesnakes, Crotalus atrox, C. lepidus and C. molossus, that inhabit the Chihuahuan Desert within the Indio Mountain Research Station (IMRS), Hudspeth County, Texas. The resting metabolic rates (RMR) of 39 rattlesnakes (C. atrox, N = 17; C. lepidus, N = 8; and C. molossus, N = 14) were determined at four experimental temperatures (20°, 25°, 30°, and 35°C). The body masses ranged from 47 to 660 g for all three rattlesnake species. The temperature coefficient of metabolism (Q10) averaged 2.8 between temperatures of 20°-30°C and 2.15 between temperatures of 25°-35°C, these are similar to other coefficients reported for large rattlesnakes such as C. adamanteus. The Q10 values for C. atrox ranged from 1.77 to 2.35, C. lepidus ranged from 2.54 to 3.32, and C. molossus ranged 2.13 to 2.75 from temperatures that ranged from 20°C through 35°C Interspecific differences in Q10 were slight or insignificant. A multiple regression relating oxygen consumption (VO2) to mass and temperature indicated that RMR increased with body mass and temperature. Interspecific oxygen consumption was statistically significant between the three species. Oxygen consumption varied between the three species due to size differences. Metabolic rates of males and females at comparable body mass for the three species of rattlesnakes were found to have no significant differences. The results indicate oxygen consumption is greatly affected by temperature and body mass. Incremental increases in temperature resulted in increased resting metabolic rates, with Q10 values within the range reported for most squamates. Assessing how environmental parameters affect physiological processes is critical to further understand the ecology and natural history of these organisms