Body temperature and body mass of hibernating little brown bats Myotis lucifugus in hibernacula affected by white-nose syndrome

Populations of hibernating bats in the northeastern USA are being decimated by white-nose syndrome (WNS). Although the ultimate cause of death is unknown, one possibility is the premature depletion of fat reserves. The immune system is suppressed during hibernation. Although an elevated body temperature (Tb) may facilitate an immune response, it also accelerates the depletion of fat stores. We sought to determine if little brown bats Myotis lucifugus Le Conte 1831 hibernating in WNS-affected hibernacula have an elevated Tb and reduced fat stores, relative to WNS-unaffected Indiana bats Myotis sodalis Miller and Allen 1928 from Indiana. We found that WNS-affected M. lucifugus maintain a slightly, but significantly, higher skin temperature (Tskin), relative to surrounding rock temperature, than do M. sodalis from Indiana. We also report that WNS-affected M. lucifugus weigh significantly less than M. lucifugus from a hibernaculum outside of the WNS region. However, the difference in Tskin is minimal and we argue that the elevated Tb is unlikely to explain the emaciation documented in WNS-affected bats.