On many days, when her lab is open, Stefanía Briones’s workstation is padded with paper towels stained with swirls of purple and blue. It looks a little like a madcap tie-dye experiment, but she is actually poking around for the bones inside bat penises. It’s a tricky task, because the bats Briones works with tend to be pretty small—just a few inches long—which means that their penises are even smaller. The bones inside them are often just millimeters long, roughly the length of a hyphen. As a research affiliate in…