Seasonal variations in the basal rate of metabolism of subtropical insectivorous bats (Nycticeius humeralis and Lasiurus seminolus): a comparison with other mammals

Abstract

The basal rate of metabolism of the evening bat (Nycticeius humeralis ) and the seminole bat (Lasiurus seminolus ) was measured at various times of the year, and its seasonal variation was compared with that of other mammals. The BMR of both species is lower than predicted on the basis of body mass (resp. 52% and 65% of expected). It shows a seasonal variation with a low during the autumn-winter period, when the foraging activity of the bats is limited. Seasonal changes in body mass and/or adiposity are unable to explain this variation. The seasonal variation observed in Nycticeius and Lasiurus is similar to that exhibited by hibernators as opposed to that shown by several small non-hibernating mammals living in cold habitats and by species inhabiting hot environments. Food accessibility and climate, two factors that are thought to explain much of the interspecific variability in mammalian BMR, also appear to be important factors influencing the pattern of intraspecific seasonal variation.