Digestion time and reemergence in the desert grassland scorpion Paruroctonus utahensis (Williams) (Scorpionida, Vaejovidae)

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Abstract
The desert grassland scorpion Paruroctonus utahensis spends most of its life in its burrow. During the active season, only about 5% of the individuals in a population appear on the surface each night. Individuals do not appear on the surface for several nights following a meal. To determine if physiological digestion time could account for this delay in reemergence after eating, I measured changes in oxygen consumption immediately following a meal. Oxygen consumption exceeded 125 μl O2g-1h-1 just after completion of a meal, then dropped to normal levels (53 μl O2g-1h-1) within 6 h. I also measured the interval between completion of the meal and subsequent defecation. All individuals defecated by 72 h following ingestion (median 12 h). In field enclosures, scorpions returned to the surface after a mean of 20.3 days (median=16) following a successful predation event. Lack of correspondence between estimates of physiological digestion time and the reappearance interval lead me to reject the idea of a long digestive pause in Paruroctonus utahensis. This conclusion lends support to the hypothesis that scorpions remain in their burrows to minimize exposure to predation.