March 16 - Love hurts for Panama's Tungara frog. The amphibian's love song beckons not only potential mates but also its moral enemy, the fringe-lipped bat. Researchers at the Smithsonian Tropical Research Institute in Panama say it's a classic conflict between two natural pressures for survival. Sharon Reich reports.
It's the sound of love...a mating call from the male tungara frog. But it might be the last sound this frog ever makes, because for the frog-eating fringe-lipped bat, it's like an invitiation to dinner. The battle between frogs and bats is one of the most intriguing in the animal kingdom -- and new research by the Smithsonian Tropical Research Institute in Panama sheds light on the evolutionary race. Researcher Rachel Page says the tungara frog is forced by circumstances to put itself in great danger during mating season. (SOUNDBITE) (English) RACHEL PAGE, Ph.D, SMITHSONIAN TROPICAL RESEARCH INSTITUTE, SAYING: "It has to call from water, not like a lot of frogs (who) call from vegetation or land. This frog cannot fully inflate the vocal sac unless it's in water. So, it makes itself very conspicuous to predators. Predators like the bat, can quickly home in on the frog via the sound of its mating call, reflecting off the ripples produced by the vocal sac in the water. The bats' powers of echolocation were put to the test in experiments with rubber frogs placed on speakers next to two trays of water. While the speakers emitted the mating calls, the water in one tray was made to ripple. When the bats were released, the researchers say nine out of ten showed a preference for the prey located next to the ripple pool. (SOUNDBITE) (English)RACHEL PAGE, Ph.D, SMITHSONIAN TROPICAL RESEARCH INSTITUTE, SAYING: "So it's this classic conflict of natural selection on the one hand and he needs to be inconspicuous, avoid predators to survive. And yet sexual selection on the other hand, without attracting a mate he can't reproduce, he can't pass on his genes. So, it's this conflict between these two opposing selection pressures." The researchers say there is hope for the tungara frog yet. The bats in the study lost their hunting advantage on ponds cluttered with leaves, which interfere with the ripples.... Although it may take another evolutionary leap before the frog learns that lesson.