Love Struck: Bats Attack Frogs After Eavesdropping on Their Serenade [VIDEO]
Frogs singing love songs to potential pond mates end up exposing themselves to predator bats, who can detect the ripples the frog creates in the water even after the love song stops.
A team of researchers from The University of Texas at Austin, the Smithsonian Tropical Research Institute (STRI), Leiden University and Salisbury University drew this conclusion by studying male túngara frogs (Physalaemus pustulosus) in Central and South America.
Writing in the journal Science, the researchers report that the túngara frogs, which spend their nights in shallow ponds serenading female frogs, will stop their song if they spot a bat flying overhead, but that the bat can still locate the frog from the ripples its love song makes, which will continue for several seconds after the song has stopped.
"A general theme of this research is that the way we communicate with any kind of a signal is by creating a disturbance in the environment," said study co-author Mike Ryan, a professor in the Department of Integrative Biology at UT Austin. "When we vocalize, we're causing changes in the air pressure around us and that's what our ears hear. When we use visual signals, light bounces off whatever pigments we're using and is transmitted to the receiver. Anything we do disturbs the environment, whether it's intended as a communication signal or not."
The scientists found that frog-eating bats (Trachops cirrhosus) were much more likely to attack a frog that made ripples in the water with its song when compared to frogs that were not disturbing the water.
The find suggests that bats use echolocation to detect the ripples.
The scientists note the misfortune of the frog that knows to stop making noise as a predator looms, only to get eaten anyway because a disturbance in the water gives his location away.
"When a frog detects the shadow of a bat overhead, his first defense is to stop calling immediately. Unfortunately for the frog, the water ripples created by his call do not also stop immediately. The ripples continue to emanate out for several seconds, creating a watery bull's-eye on the frog. Bats use the ripples, thereby beating the anti-predator strategy," said lead author Wouter Halfwerk, a behavioral biologist affiliated with UT Austin and STRI.
In an interview with Reuters, Halfwerk likened the process to covert espionage.
"Imagine the frog that's in a pond," he said. "It's like it's being spied upon by some agent that is spying on your communications. You try and make your love song and all of a sudden, yeah, you're screwed because someone is listening in on your call by using a completely different communication channel."
With one quick swoop, a hungry bat can finish the frog, cutting short its love song and its life.
"I wouldn't like being in the same situation," Halfwerk said. "It frightens me a little bit."