Male bats with high testosterone levels have large forearm crusts when females are fertile

Males may put a lot of effort into attracting females. Male peacocks flaunt eye-catching trains, but male bats, because they are active at night, may rely on females' sense of smell to draw them in. Three years ago, Victoria Flores, a predoctoral fellow at the Smithsonian Tropical Research Institute (STRI) in Panama, discovered that male fringed-lipped bats often have a sweet-smelling, crusty substance on their forearms. Because only males had crusts and primarily exhibited these crusts during the putative reproductive season, Flores speculated that crusts might play a role in mating. Now Mariana Muñoz-Romo, postdoctoral fellow at STRI and National Geographic Explorer, and her colleagues have evidence to prove it.