(AR)Scaling of standard metabolic rate in estuarine crocodiles Crocodylus porosus

Abstract

Standard metabolic rate (SMR, ml O2 min−1) of captive Crocodylus porosus at 30 °C scales with body mass (kg) according to the equation, SMR = 1.01 M0.829, in animals ranging in body mass of 3.3 orders of magnitude (0.19–389 kg). The exponent is significantly higher than 0.75, so does not conform to quarter-power scaling theory, but rather is likely an emergent property with no single explanation. SMR at 1 kg body mass is similar to the literature for C. porosus and for alligators. The high exponent is not related to feeding, growth, or obesity of captive animals. The log-transformed data appear slightly curved, mainly because SMR is somewhat low in many of the largest animals (291–389 kg). A 3-parameter model is scarcely different from the linear one, but reveals a declining exponent between 0.862 and 0.798. A non-linear model on arithmetic axes overestimates SMR in 70 % of the smallest animals and does not satisfactorily represent the data.