DETERMINANTS OF THE POSTFEEDING METABOLIC RESPONSE OF BURMESE PYTHONS, PYTHON MOLURUS

The relatively large meal sizes consumed by sit-and-wait-foraging snak e species make them favorable for investigating specific dynamic actio n, the rise in metabolic rate associated with digestion. Hence, we mea sured O-2 consumption rates (VO2) before and up to 20 d after Burmese pythons (Python molurus) either had only constricted and killed rodent meals or had also been allowed to consume meals ranging in size from 5% to 111% of their body mass. Postprandial VO2 peaked within 2 d at a value that increased with meal size, up to 44 times standard metaboli c rate for the largest meals. In addition to being the largest known m agnitude of postprandial metabolic response, this also exceeds the fac torial increase in VO2 during peak physical activity for all studied a nimals except perhaps racehorses. Specific dynamic action, calculated from the extra VO2 above standard metabolic rate over the duration of digestion, increased with meal size and equaled 32% of ingested meal e nergy. The allometric exponent for body mass was 0.68 for standard met abolic rate, 0.90 for peak postprandial VO2, and 1.01 for specific dyn amic action. Specific dynamic action is higher, and standard metabolic rate is lower, in sit-and-wait-foraging snake species than in activel y foraging snake species. This suggests that sit-and-wait-foraging sna kes, which consume large meals at long and unpredictable intervals, re duce standard metabolic rate by allowing the energetically expensive s mall intestine and other associated organs to atrophy between meals bu t thereby incur a large specific dynamic action while rebuilding those organs upon feeding.