Glow Up! New discovery of fluorescing lesser horseshoe bats (Rhinolophus hipposideros)
An exciting discovery has been published, showing that two European horseshoe bats — the lesser horseshoe bat (Rhinolophus hipposideros) and the Blausis bat (Rhinolophus blasii) — can glow in the dark. Henry Schofield (VWT's former Head of Conservation) and team discovered this bizarre phenomenon last year and realised differences between species and the findings could be used as a new survey tool.
While previously, bats with glowing toes had been discovered in Mexico, this is the first time that whole body fluorescing under UV light has been recorded.
This glowing in the dark under a UV light only occurs in adults. This phenomenon is also observed in the Blausis horseshoe bat, but not in other European horseshoe bat species. The technique can improve survey efforts to identify species and maternity colonies.”
The fluorescence in R. hipposideros was only observed in adult bats of both sexes and not in juveniles (at least until they were six months old). It is unlikely that this phenomenon has any function in the ecology or behaviour of the species, as rhinolophids lack the eye structure that would enable them to detect light emitted at these wavelengths. It may also be a negative feature since some nocturnal predators may have the ability to detect the fluorescence. But for bat conservationists, potentially, the different responses of adults and juveniles have uses in the monitoring of species, especially concerning confirming maternity colonies and estimates of the productivity of colonies. In the case of R. blasii, it may also aid in the identification of this generally hard to spot species that often roosts with other medium-sized horseshoe bats. R. blasii is a cryptic species that roosts with R. euryale in some areas of Europe and the two species are difficult to separate without catching and handling the bats. The use of UV-torches to determine whether R. blasii is present and if so, what proportion of the mixed colony they comprise would be a non-invasive means of monitoring this species.
The UV fluorescence demonstrated by the adults of these bats may also provide those monitoring their population status with an additional tool. Counts of glowing bats versus those not fluorescing inside roosts or as they emerge could be a new tool for identifying maternity roosts and estimating the productivity of single species colonies.