Oxygen consumption, temperature, and water loss in bats from different environments

Abstract

A hibernating bat Eptesicus fuscus from North Carolina and a migratory species from Arizona were compared. At ambient temperatures below 30 C both species could be either torpid or active. In torpor the body temperature was within 1-2 C of the ambient temperature, and the metabolism was correspondingly reduced. Active bats maintained body temperature 32-36 C, and metabolism increased at low air temperatures. Thermoneutral zones and basal metabolic rates were determined. Over 30 C only the active metabolic state was recognizable. At high temperatures evaporative water loss increased greatly. Although water loss per milliliter of O2 used was lower for Tadarida than for Eptesicus, it was still higher than that found for desert rodents. Torpid bats lost one-half to one-third as much water by evaporation as active bats, and torpor can be regarded as a water-saving mechanism as well as an energy-conserving device.