Frogs mating call betrays their location to predatory bats, researchers from the Smithsonian Tropical Research Institute, Leiden University, The University of Texas, and Salisbury University have discovered. Tungara frogs live in Central and South America, inhabiting shallow puddles. They croak out mating calls to find mates, and although it’s hard to predict if any females will be interested, the male frogs often get more than they bargained for. Predatory bats fly the skies above the frogs and often dive down to snatch them from their puddle homes. Although the frogs have learned and evolved to detect the silhouettes of bats flying over head and stop their call to avoid being spotted, the bats have countered by beginning to use the ripples in the puddle caused by the calling to find and eat the frog even after they have gone silent.
Although the ripples often cause an end to the frog, research showed that it was not without a benefit. The Tungara frogs mating call that betrays their location to predatory bats includes two parts, a whine part and a chuk part. The whine is the part that attracts females, but the chuk makes the call more desirable. The frog makes the call by inflating and deflating a sac of skin on its neck, and its this that causes the ripples. The chuck is specifically responsible for making the ripples around the frog as it sits in the water, turning looking for a date into a gamble between finding love and being dinner. Although the bats can hear the frogs and find them without the help of the ripples, tests showed bats descending on frogs in rippling puddles nearly 40 percent more often still water. Researchers are theorizing that bats are able to use their echo-location abilities to see the ripples as a bull’s eye around the frog that has gone silent. Although they are using their only known trick to avoid detection, the Tungara is betrayed by the slow to stop ripples. Even though it has gone silent, the frog is a clear target to a bat using the ripples as a marker.
Mike Ryan, a researcher at UT Austin, points out that the frogs unfortunate scenario is chock full of information useful to us as well. Pointing out that all methods of communication create a disturbance in the environment, be they calls or lights or smells. Although the frogs are all aware of the air pressure changes interpreted as sound, they are not paying attention to the ripples caused in the water around them. This is what the bats have learned to monopolize on, as they often lose the frog when searching with sound alone, since the frog stops calling as soon as it sees the bat. Since the ripples caused by the frogs mating call betrays their location to predatory bats, Tungaras find themselves in a very difficult situation. Looking at this way, what’s a frog to do when confronted with the choice of mating or being eaten by a giant bat?
By Daniel O’Brien