Metabolic response to feeding and fasting in the water python (Liasis fuscus)

Compared with other reptiles, pythons have a relatively low standard metabolic rate (SMR) when post-absorptive, but metabolism increases substantially after feeding. This study examined the effects of feeding and fasting on adult and hatchling water pythons (Liasis fuscus). We compared ratios of peak digestive metabolic rate (PDMR) after feeding with the metabolic rate of both post-absorptive (SMR) and fasted water pythons. If metabolic rate of a fasting snake is taken as 'SMR', then the ratio PDMR/SMR becomes increasingly exaggerated as fasting continues. After 56 days of fasting in adults, or after 45 days in hatchlings, the metabolic rate of water pythons was significantly lower than that of post-absorptive animals. Peak digestive metabolic rate of post-absorptive adult water pythons was only 6.3-12.0 times SMR, but the ratio was twice that if fasted (metabolically depressed) animals were used to determine the 'SMR' denominator. Thus, this ratio should be used with caution. Peak digestive metabolic rate after feeding increased with increasing meal size for meals less than 20% of body mass, but PDMR did not increase for meals between 20% and 39% of body mass for adult water pythons. Similarly, the PDMR did not increase significantly between 25% and 50% meal sizes for hatchlings. The digestive physiology of water pythons is apparently better suited to frequent meals of relatively small prey compared with the digestive physiology of some other pythons.