For researchers on the Mediterranean coast of Spain, near Valencia, the mystery began when bat excrement on the floor of a cave turned out to be loaded with scales, suggesting that an insect-eating bat species had instead turned to fishing.
It wasn’t a complete surprise. Bats are amazingly diverse, with 1,240 species (that’s 20 percent of all mammals), and they’ve had 50 million years to develop a multitude of quirky behaviors. Different bat species are known to eat almost anything—insects, of course, but also fruit, leaves, flowers, nectar, pollen, and, yes, blood. It might be genuinely surprising if somebody said bats catch and eat songbirds, except that researchers caught bats doing just that in 2007.
Frogs too. Early this year, researchers in Central and South America reported on how the male túngara frog’s love song produces a widening pattern of ripples on the surface of the water. Bats have learned to use that pattern as a flight path to cruise in and pluck up the unfortunate Lothario for dinner.
Still, Ostaizka Aizpurua-Arrieta and her coauthors on a new study in the journal PLOS One wanted to find out how Spain’s long-fingered bat learned to fish. “It was a special challenge for me because we didn’t think fishing was among the habits of the long-fingered bat,” says Aizpurua-Arrieta. These bats use echolocation to hunt down their main food source, immature midges, at the surface of the water. But the sonic pulses the bats emit for echolocation can’t penetrate below the surface, to where fish live. The long-fingered bat also weighs no more than a third of an ounce, which is “why it is difficult to imagine it fishing.”