The Behavior of Temperate Cave Bats in a Subtropical Environment

Abstract

This study seeks to determine how temperate bats react to subtropical climates in which flying insects are available throughout the year and in which cave microclimates in winter are appreciable warmer than those typical of temperature climates. The cave temperatures selected by bats in a cold climate are negatively correlated with their body weight; clusters of bats select even colder temperatures. The temperature differential that a bat (or a cluster) maintains with the environment is also a function of body weight (and thus cluster size), rate of metabolism and Q 1 0 . Only bats that are both small and nonclustering are capable of hibernating at environmental temperatures above 14°C. Therefore, the small Pipistrellus subflavis is the only cave bat that hibernates for an extended period in Florida. Myotis grisescens, a large species, is limited to caves in northernmost Florida, and much of that population migrates northward to winter in Alabama, where the cave temperatures are low enough for large clustering bats to remain in torpor for extended periods. Myotis austroriparius, an intermediate—sized species, remains active for the entire year in Florida, although it probably spends more time in torpor in the northern than in the central part of the state. The seasonal pattern of fat deposition in bats is correlated with their hibernal behavior: large fat deposits are found both in M. grisescens and P. subflavus, whereas those in M. austroriparius are larger in northern than in central Florida. Some temperate bats, such as M. grisescens and P. subflavus, do not seem able to eliminate hibernation to take advantage of the nearly continuous food supply in warmer climates. Rather, these species appear to be obligatory hibernators. In these species most of the copulation occurs in fall and winter, which in turn requires that the females remain torpid if pregnancy is to be delayed to spring. In warm climates this behavior is impossible for large or clustering species that require extended periods of torpor. Such species are thus excluded from a subtropical environment.