Dive duration is determined by the oxygen stores of the body and diving metabolic rate. Digestion in infrequently feeding ectotherms, such as snakes is energetically demanding and enduring - a potential conflict for oxygen resources for diving animals. I tested the effect of digestion of various meal sizes on the diving behaviour of the Arafura filesnake and found significant reductions in dive duration with all meal sizes. With the largest meal, dive times reduced to 20% (~5 min) of pre-feeding dive times. Even with the dramatic reduction in dive times, snakes still dived for longer than what was predicted by the calculated aerobic dive limit (cADL) which calculates theoretical maximum aerobic dive times based on metabolic rate and oxygen stores. The use of cutaneous aquatic respiration is believed to partially account for this given that during digestion, snakes up-regulated their use of aquatic oxygen above pre-feeding levels.

Effect of temperature and aquatic oxygen levels on diving behaviour
Temperature and aquatic oxygen levels are expected to influence the metabolic rate and diving behaviour of the Arafura filesnake due to the effects on metabolic rate and capacity for aquatic respiration respectively. I tested the effects on metabolic rate and dive duration by exposing snakes to temperatures of 20, 26 and 32C in both normoxic (155mmHg) and hypoxic (20-40mmHg) aquatic conditions. I found that increasing temperature both increased metabolic rate and decreased dive time. Under aquatic hypoxia, aerial respiration increased to compensate for the significantly reduced potential for aquatic respiration and dive duration further decreased. Fluctuations in temperature and aquatic oxygen levels would be expected in billabongs where filesnakes inhabit and any reduction in dive time caused by environmental factors or physiological processes (eg. digestion) may increase the exposure of snakes to both aerial and aquatic predators. The effect of predators on the filesnake diving behaviour is next to be studied.