Fig. 8.

A) Basal and minimum metabolic rate as a function of body mass. Regression equations for mass specific BMR were log₁₀BMR= −0.444 – 0.308 log₁₀BM (t= −13.9, P<0.0001,R²=0.73) among mammals and log₁₀BMR= −0.415 – 0.412 log₁₀BM (t= −4.33, P<0.001,R²=0.66) among birds. Minimum MR also decreased as body mass increased in mammalian daily heterotherms (log₁₀MR= −0.917-0.192 log₁₀BM, t=−2.30, P=0.025, R²=0.19). In avian daily heterotherms the slope of this regression was not significantly different from zero (t=−1.17, P=0.25). Among hibernating mammals the decrease of minimum metabolic rate with body mass was not pronounced but statistically significant (log₁₀MR= −1.579 – 0.116 log₁₀BM, t= −4.41, P=0.0001, R²=0.13). B) The relationship between minimum torpor metabolic rate and maximum torpor bout duration. TBD_max decreased with increasing TMR_min among mammalian hibernators (log₁₀TBD_max=1.22-0.862 log₁₀MR, t=−4.56, P<0.0001, R²=0.20). A weaker relationship in the same direction was also detectable among mammalian daily heterotherms (log₁₀TBD_max=0.76-0.475 log₁₀MR, t=−3.92, P<0.001, R²=0.27), but not in avian daily heterotherms (t=−1.37, P=0.205).