The scaling of metabolic rate in reptiles at low temperature

Basal metabolic rate has been shown to scale with body mass to the 3/4 power across a wide range of vertebrate groups. However, actively hibernating mammals appear to be an exception to this rule as they deviate from the 3/4 power scaling relationship at low body temperatures, such that metabolic rate is nearly independent of body size at low temperature. We investigated whether the relationship between body mass and metabolic rate at low temperature in ectothermic vertebrates resembles that seen in hibernating mammals. Specifically, we asked whether deviation from the relationship between body mass and metabolic rate at low temperatures is a phenomenon specific to mammalian hibernation or whether reptiles respond in a similar manner. Standard metabolic rate will be measured at 30°C, 20 °C, and 4°C in Green Iguanas, Eastern Fence lizards, and Green Anoles, spanning 3 orders of magnitude in body mass and the scaling relationship between standard metabolic rate and body mass at each of the 3 temperatures will be determined by linear regression. The maintenance of the 3/4 power scaling relationship in reptiles would suggest a temperature independent mechanism of metabolic depression specific to small mammalian hibernators, whereas a reduction of the scaling exponent in reptiles would suggest that the absence of the 3/4 scaling relationship is a general phenomenon among vertebrates at low temperatures.