Comparisons of differential warming rates and tissue temperatures in some species of desert bats.

-An examination of warming rates of chest muscle in relation to rectal temperature and subsequent thermal mapping of selected tissues in active bats has shown the following trends: 1. During arousal, chest muscle warms slightly faster than rectal temperature in Pipistrrllus hasperus. .411fro:ous pullidus, MJsotis califbrnicus, M. thysanodes. Eptesicus fuscus, and Tudarida hrusiliellsis. whereas in Plrcorus towtlsendii chest muscle warms twice as fast as rectal. 2. Bats that warmed sufficiently to initiate flight in the laboratory had interscapular temperatures that wcrc higher than rectal, brain. or adjacent flight muscles. 3. Field data. however, indicate interscapular temperatures to be lower than flight muscle temperature, especially following periods of sustained flight. 4. Both laboratory and field data show that certain bats are capable of coordinated and sustained flight at tissue temperatures well below recognized homeothermic levels.