Sounds like trouble

Natural History, Oct, 2002 by Stephan Reebs

In Africa, terrestrial animals respond in one of two ways to advancing savanna fires: by burrowing into the ground or running for their lives. For those who try to flee but aren't very fast, a little forewarning can mean the difference between life and death. One such animal is the West African reed frog (Hyperolius nitidulus). In summer, reed frogs ding to grass stems or dry leaves. They remain motionless to conserve water, but the sound of distant fire can rouse them to action. German biologists T. Ulmar Grafe, Stefanie Dobler, and K. Eduard Linsenmair, of the University of Wurzburg, played a recording of a savanna fire to reed frogs that were peacefully estivating in Ivory Coast's Comoe National Park. Eighteen out of twenty frogs listened for a few minutes and then took off in the direction of tall trees or dense bush at a forest edge (these critters are good climbers, and tall structures offer protection from ground fires). None of the frogs reacted to white noise, and only six moved in response to the fire sounds played backward. Why do the frogs spend precious moments listening before they leap toward safety? Perhaps, the biologists suggest, the frogs want to make certain that the crackling sounds are fire and not dry sticks breaking under a large animal's footsteps. Scientists already knew that various nonhuman animals use smoke, heat, and visual information to perceive distant fire, but this is the first example of acoustic detection. ("Frogs flee from the sound of fire," Proceedings of the Royal Society of London B 269, 2002)

Stephan Reebs is a professor of biology at the Universite de Moncton in New Brunswick, Canada, and the author of Fish Behavior in the Aquarium and in the Wild (Cornell University Press).