Continuous light inside a cave abolishes the social synchronization of the circadian rhythm in a bat

Abstract

The bat Hipposideros speoris regulates its flight activity rhythm in the absence of time cues in a totally dark natural cave. The flight activity rhythm even of captive bats in total darkness entrained to the social cues available from free flying conspecifics. The social synchronization of the circadian rhythm was abolished in continuous illumination (LL) of 10-20 lx. All the captive bats 'feerun' in LL with τ longer than 24 h. The social entrainment was re-established following a few cycles of transients when total darkness was restored.