"Singing" PenisAlthough not the loudest animal in terms of sheer decibels, the 0.07-inch (2-millimeter) water boatman species Micronecta scholtzi, pictured, does make the loudest sounds relative to its body size, scientists announced in June in the journal PLoS ONE.Engineers and evolutionary biologists in Scotland and France recorded the boatman—which is roughly the size of a grain of rice—"singing" in a tank. The aquatic insect's songs peaked at 105 decibels, roughly equivalent to the volume of a pounding jackhammer within arm's reach.The chirps are loud enough that humans can hear the sounds while standing at the edge of a boatman's pond. Fortunately for nature lovers, though, nearly all the sound is lost when the noises cross from water to air.Remarkably, the boatman creates his songs by rubbing his penis against his belly, in a process similar to how crickets chirp. Sound-producing genitalia are relatively rare within the animal kingdom, but animals have evolved hundreds of other ways to boost their hoots, howls, and snaps.—Rachel Kaufman

Photograph courtesy Jerome Sueur, MNHN