POSTEXERCISE THERMOREGULATORY BEHAVIOR AND RECOVERY FROM EXERCISE IN DESERT IGUANAS

Desert iguanas (Dipsosaurus dorsalis) undergo respiratory recovery mor e rapidly and incur lower energetic costs when they recover from 40 de grees C burst activity at 20 degrees C than when they recover at 40 de grees C. However, a body temperature of 20 degrees C falls well outsid e the preferred activity temperature range of this species, and impose s several physiological and behavioral Liabilities. To determine if ex hausted animals would favor a thermal regimen that allows for rapid an d 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 signif icantly to a mean temperature of 33.5 degrees C during the first 60 mi n of recovery, and subsequently rewarmed themselves to an average temp erature of 38 degrees C for the remainder of their recovery period. Co ntrol animals maintained a constant body temperature of 37.7 degrees C throughout the 180-min recovery period. We then exercised animals to exhaustion at 40 degrees C and allowed them to recover for 180 min und er a thermal regimen that mimicked that selected by exhausted animals in the previous experiment. Animals recovering under this thermal regi men returned to rates of O-2 consumption, removed exercise-generated b lood lactate, and incurred energetic costs that were more similar to d ata previously collected for animals recovering from exercise at a con stant 40 degrees C than to data from animals recovering at 20 degrees C. These results suggested that the energetic benefits associated with recovery at 20 degrees C are not of sufficient biological importance to cause a major shift in thermoregulatory behavior. Copyright (C) 199 7 Elsevier Science Inc.