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article imageBats use echolocation to hunt for túngara frogs

By Tim Sandle     Sep 3, 2014 in Science
A new study has shown how male túngara frogs are easily detected and eaten by bats. Because the frogs bellow, the bats can find them through echolocation.
The research indicates that the Central American amphibians’ balloon out their vocal sac as parts of a sexual display to attract females. This mating ritual allows bats to sense the presence of the frog.
Biologists observed how the inflated vocal sac of the male túngara (Physalaemus pustulosus) almost matches their full body size. As the frog does this, fringe-lipped bats (Trachops cirrhosus) are able to hunt the males. The fringe-lipped bat is a leaf-nosed bat from southern Mexico to Bolivia and southern Brazil.
The biologists were interested in how senses other than hearing guide the bats. For the research, The Scientist reports, the biologists placed ten wild fringe-lipped bats into netted enclosures with two lifelike rubber imitations of male túngaras (“robofrogs”). The robofrogs played mating calls, however only one of the imitation frogs had a billowing vocal sac. The other frog’s sac remained deflated.
The scientists observed that the bats almost always hovered over the robofrog sporting a puffing sac. Further investigation showed that darkness did not stop bats from detecting the robofrogs. This ruled out the involvement of vision. However, in a study where a plastic cup was placed over the frog’s vocal sac, the bats could not locate the frog. This suggests that the hunt requires echolocation. This idea was further supported when an ultrasonic microphone was situated in front of the fake frogs. The microphone detected the signature sound waves of the bats’ echolocation chirps.
The findings have been reported to the Journal of Experimental Biology. The paper is titled “Risks of multimodal signaling: bat predators attend to dynamic motion in frog sexual displays.”
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