Energetic costs of digestion in Australian crocodiles

Abstract

We measured standard metabolic rate (SMR) and the metabolic response to feeding in the Australian crocodiles, Crocodylus porosus and C. johnsoni. Both species exhibit a response that is characterised by rapidly increasing metabolism that peaks within 24h of feeding, a postfeeding metabolic peak (peak VO2) of 1.4–2.0 times SMR, and a return to baseline metabolism within 3–4 days after feeding. Postfeeding metabolism does not significantly differ between species, and crocodiles fed intact meals have higher total digestive costs (specific dynamic action; SDA) than those fed homogenised meals. Across a moret han100-fold range of body size (0.190 to 25.96 kg body mass),SMR,peak_VO2,and SDA all scale with body mass to an exponent of 0.85. Hatchling (<1 year old) C. porosus have unexpectedly high rates of resting metabolism, and this likely reflects the substantial energetic demands that accompany the rapid growth of young crocodilians