Comparison of Variables of Torpor Between Populations of a Hibernating Subtropical/Tropical Bat at Different Latitudes

Abstract

Torpor use differs among heterothermic species and data comparing populations of a single hibernating species at different latitudes could reveal how animals adapt to different climates. I investigated variables of torpor in free-ranging Nyctophilus bifax, a hibernating subtropical/tropical insectivorous microbat, during winter from a subtropical region and a tropical region. Mean torpor bout duration was significantly shorter and mean minimum skin temperature of torpid bats was significantly higher in the tropical population in comparison to the subtropical population. In both populations torpor bout duration was negatively correlated with ambient temperature and the slope of this relationship differed significantly (P = 0.02) between the populations when examined under the same thermal conditions. The differences found in these variables of torpor were most likely due to regional differences in weather and insect abundance and suggest that populations of heterothermic mammals can adapt or acclimatize to the local climate of the habitat that they occupy, even when thermal conditions are mild.