Resting metabolic rates in boid snakes: allometric relationships and temperature effects.

Resting metabolic rates (RMR) of 34 species from 18 genera of boas and pythons (Serpentes: Boidae), with body masses ranging from 2 to 67,800 g, were determined as oxygen consumption (VO2) and carbon dioxide production (VCO2) at three ambient temperatures (Ta). The temperature coefficient of metabolism (Q10) averaged 2.61 between Ta of 20-30 degrees C and 2.65 between 30 and 34 degrees C. The respiratory exchange ratio RE (= VCO2/VO2) increased slightly with increasing Ta (0.795 at 20 degrees C, 0.819 at 30 degrees C, and 0.834 at 34 degrees C). Interspecific differences in Q10 and RE were slight or insignificant. A multiple regression relating metabolism (VO2) to mass and Ta explained 97% of the variance in the pooled interspecific data. The mass exponent was 0.806, which is approximately the same as reported for squamates and for all reptilian taxa combined. The mean within-species slope (0.732) was significantly less than the slope for pooled data, but did not differ significantly from 0.75. In 40 of 42 cases (14 species at 3 Ta), within-species slopes did not differ from each other. Values of the adjusted mean Y, from covariance analysis, were significantly and positively correlated with mass, indicating that the mass coefficient increases with increasing mass. Considerable variation in metabolic rate is apparent both within and between ecological and taxonomic categories.