Social Effects of Roosting on the Metabolism of the Pallid Bat (Antrozous pallidus)

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Abstract
In summer and autumn, pallid bats in Arizona may be found roosting during the daytime in temperature-stable crevices which vary from 28° to 31° centigrade (C) over a 24-hour period. The bats are heterotherms. They are colonial and roost in clusters. We analyzed body temperature, oxygen consumption, and weight loss of bats roosting individually and bats roosting in clusters, using adult males, adult females, and immature females in our analysis. Analysis was carried out while the bats were roosting in an incubator and in Plexiglas chambers at 15°, 20°, 25°, 30°, and 35°C. We used oxygen consumption and weight loss as indicators of metabolism. At all temperatures tested, bats roosting individually had higher mean oxygen consumption and weight loss values than bats roosting in a cluster. There were no significant differences due to sex, and in a cluster there were no significant differences in body temperature between bats on the periphery and those in the center. This implies that there are no sex-related or physiological factors underlying the metabolic advantages to roosting in a cluster. At 30°C, the oxygen consumption of both individual and clustered bats was lower than at 25°C or 35°C. We conclude that the bats require the sociality of roosting in clusters to conserve metabolic energy in daytime roosts most effectively, and that the bats are metabolically best adapted for roosting at temperatures near 30°C.