Ultraviolet-induced photoluminescent bristles on the feet of the Mexican free-tailed bat (Tadarida brasiliensis)

We describe ultraviolet-induced photoluminescent structures in a nocturnal mammal: the Mexican free-tailed bat (Tadarida brasiliensis: Molossidae). Twenty-four individuals from two roosts near Mexico City were captured and photographed under white and ultraviolet light to corroborate the findings. All 24 presented the same ultraviolet-induced cyan photoluminescent combs of bristles on digits one and five of the feet, as well as some longer photoluminescent hairs on the toes and the edge of the uropatagium. Four individuals of another species sharing one of these roosts, the cave myotis (Myotis velifer: Vespertilionidae), were also captured and photographed, but none exhibited this striking pattern. A further individual of T. brasiliensis was captured opportunistically and photographed in Coahuila, around 700 km away, also showing these photoluminescent bristles. Photoluminescence in museum specimens was ambiguous. This is the first molossid bat for which a photoluminescent structure has been described. It remains to be seen whether any function exists, such as intraspecific communication.