Postexercise Thermoregulatory Behavior and Recovery From Exercise in Desert Iguanas

Abstract

Wagner, E. L. and T. T. Gleeson. Postexercise thermoregulatory behavior and recovery from exercise in desert iguanas. Physiol Behav 61(2) 175–180, 1997.—Desert iguanas (Dipsosaurus dorsalis) undergo respiratory recovery more rapidly and incur lower energetic costs when they recover from 40°C burst activity at 20°C than when they recover at 40°C. However, a body temperature of 20°C falls well outside the preferred activity temperature range of this species, and imposes several physiological and behavioral liabilities. To determine if exhausted animals would favor a thermal regimen that allows for rapid and inexpensive respiratory recovery, we exercised lizards to exhaustion and allowed them to recover in a laboratory thermal gradient for 180 min. Recovering animals allowed their body temperatures to cool significantly to a mean temperature of 33.5°C during the first 60 min of recovery, and subsequently rewarmed themselves to an average temperature of 38°C for the remainder of their recovery period. Control animals maintained a constant body temperature of 37.7°C throughout the 180-min recovery period. We then exercised animals to exhaustion at 40°C and allowed them to recover for 180 min under a thermal regimen that mimicked that selected by exhausted animals in the previous experiment. Animals recovering under this thermal regimen returned to rates of O2 consumption, removed exercise-generated blood lactate, and incurred energetic costs that were more similar to data previously collected for animals recovering from exercise at a constant 40°C than to data from animals recovering at 20°C. These results suggested that the energetic benefits associated with recovery at 20°C are not of sufficient biological importance to cause a major shift in thermoregulatory behavior.