Recaptured Myotis brandtii carried glue-on radio-tag for 10 months: does time from tagging to shedding depend on timing of annual moulting?

The use of radio telemetry has been essential for collecting information about bat biology and ecology.The radio-tag is usually glued on the back of the bat and typically falls off after just over a week.In the present study, we present a case where a radiotagged Myotis brandtii was recaptured with its radio-tag still intact and attached, ten months after initial tagging.At the time of recapture, there was no re-growth of hair under the transmitter.Three other radio-tagged Myotis mystacinus were also recaptured after the winter season, but these individuals had shed their radiotags and showed a complete regrowth of hair.Carrying a non-functional transmitter will cause unnecessary costs for the bat.As the onset of moulting is understudied in general, and differs widely between both species, sexes and sexual status, we propose that researchers should put more effort into recapturing radio-tagged bats before the end of the transmitter's battery life to remove the transmitter.This may be particularly important when the time of tagging does not correspond with the bats' moulting season.More intra-and interspecific information is needed about the timing of moulting in order to minimize negative effects on bats when using glued on radio-tags.