Effect of Activity Duration on Recovery and Metabolic Costs in the Desert Iguana (Dipsosaurus dorsalis)

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Biology (HMC)

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The majority of elevated O2 consumption associated with short and vigorous activity occurs during recovery, thus an assessment of associated metabolic costs should also examine the excess post-exercise oxygen consumption (EPOC). This study examined O2 uptake during exercise, EPOC and distance traveled during 5-, 15-, 60- and 300-s sprints at maximal treadmill intensity in Dipsosaurus (N=10; 74.3±2.1 g). EPOC (0.08, 0.14, 0.23 and 0.18 ml O2 g−1, respectively) was large (80–99% of total elevated O2 consumption) and increased significantly between 5 and 60 s. The cost of activity (Cact; ml O2 g−1·km−1), intended to reflect the total net costs associated with the activity, was calculated as the total elevated O2 consumption per unit distance traveled. Cact decreased with activity duration due to proportionally larger increases in distance traveled relative to EPOC volume, and is predicted by the equation Cact=14.7×activity duration (s)−0.24. The inclusion of EPOC costs provides an ecologically relevant estimate of the total metabolic cost of locomotor activity. Cact exceeds standard transport costs at all durations examined due to the addition of obligate recovery costs. The differences are large enough to impact energy budget analyses for ectotherms.

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Copyright © 2001 Elsevier Science Inc. All rights reserved.