Frogs often use loud and distinct mating calls to attract mates. However, it seems that these mating calls can also be the sound of the death knell for frogs whose calls can cause the formation of ripples in the water. A new study shows that bats that like to prey on frogs can use these ripples to home in on their prey.

A team of researchers from various institutions conducted the recent study. The team, which was comprised of researchers from the Smithsonian Tropical Research Institute, the University of Texas, Salisbury University and Leiden University; found that the mating calls of the male túngara frog causes ripples on the surface of water. Since túngara frogs often lie in shallow pools of water, the calls can disturb the water surrounding, causing distinct ripples that other animals may perceive, especially bats that like to prey on these animals use echolocation to find the frogs. While the túngara frogs may stop their mating calls once they see a bat flying overhead, the bats can still use echolocation to detect the ripples on the water surface, which persist even after the mating calls have stopped.

"Animal displays are often perceived by intended and unintended receivers in more than one sensory system," says the research team. "In addition, cues that are an incidental consequence of signal production can also be perceived by different receivers, even when the receivers use different sensory systems to perceive them."

Túngara frogs, which are indigenous to South America, have a very distant mating call and can sound like alternating vocalizations similar to "whines" and "chucks." The calls are created when the frogs take in and expel air using a specialized vocal sac. Due to the inflation and deflation of the sacs that are partially submerged in water, distinct ripples form on the surface of the water with the frog sitting dead center of the concentric rippling pattern.

"Here we show that the vocal responses of male túngara frogs (Physalaemus pustulosus) increase twofold when call-induced water ripples are added to the acoustic component of a rival's call," says the team. "Hunting bats (Trachops cirrhosus) can echolocate this signal by-product and prefer to attack model frogs when ripples are added to the acoustic component of the call."

Love call for some. Dinner call for others.