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.
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Acknowledgments
We thank the Australian Research Council linkage grant (LP0882478), the Rural Industries Research and Development Corporation, the Northern Territory Research and Innovation Fund, and Wildlife Management International for funding. We are grateful to staff at WMI for technical support, including J. Carrigan, S. Coulson, D. Ottway and J. Pomeroy, who helped build the respirometry chambers and handle the animals. We thank Gordon Grigg for commenting on a draft and supplying references, Gary Packard for carrying out the non-linear regression, Craig White for analytical advice and Doug Glazier and two referees for comments on early versions.
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Communicated by I.D. Hume.
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Seymour, R.S., Gienger, C.M., Brien, M.L. et al. Scaling of standard metabolic rate in estuarine crocodiles Crocodylus porosus . J Comp Physiol B 183, 491–500 (2013). https://doi.org/10.1007/s00360-012-0732-1
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DOI: https://doi.org/10.1007/s00360-012-0732-1