Some bats keep flying in a light drizzle, but they take shelter when there's serious rain. A new study published online today in Biology Letters finds one reason why: Bats have to work harder to fly when their fur and wings are wet. In a series of trials in Costa Rica, scientists studied Sowell's short-tailed fruit bats as they flew around a large octagonal cage. Sometimes they first dampened the bats with tap water; sometimes the bats flew wet and in the rain. Bats used about twice as much energy when they were wet as when they were dry, the team found. Flying in the rain didn't make a difference, which ruled out some kind of mechanical problem caused by raindrops hitting wings, nor did the actual weight of the water. The scientists think that wet bats, like most wet mammals, are cold, so they have to work harder to stay warm. And with water mussing their silky fur and dampening their wings, bedraggled bats might also be less aerodynamic.
See more ScienceShots.