Red-eyed tree frogs use sound and vibration for companion calls and aggression

Credit: Pixabay/CC0 Public Domain

One would be hard pressed to walk outside without hearing the animals calling. During the day, birds chatter back and forth, and as night falls, frogs and insects call out to defend territories and attract potential mates. For several decades, biologists have studied these calls with great interest, dismissing key lessons about the evolution of animal displays and speciation processes. But there may be a lot more animal calls than we realized.

A new study appears in Journal of Experimental Biology by Dr. Michael Caldwell and student researchers at Gettysburg College demonstrate that the calls of red-eyed tree frogs not only send sounds through the air, but also send vibrations through plants. What’s more, these plant vibrations change the message of others frogs Receive in major ways. The researchers played the sounds and vibrations generated by the male’s call to other red-eyed tree frogs surrounding a rainforest pond in Panama. They found that female frogs were twice as likely to choose potential mate calls if those calls included both sound and vibrations, and male frogs were more aggressive and displayed a greater range of aggressive displays when they sensed vibrations from their competitors’ calls.

“This really changes how we look at things,” Caldwell says. “If we want to know how a call works, we can’t just look at the sound it makes anymore. We need to at least look at the roles that associated vibrations play in delivering the message.”






The tree-eyed male responds to the sounds and vibrations of a rival male’s call by producing aggressive vibrational signals. Credit: Dr. Michael Caldwell

Because vibrations are unavoidably stimulated at any surface that a calling animal touches, the authors of the new study suggest that it is likely that many species communicate using similar “bimodal voice calls” operating simultaneously through both airborne and ground sound, or Waterborne vibrations.

Caldwell says, who points out that researchers in University of California and the University of Texas It reports similar results with distantly related frog species, and elephants and many insect species have been shown to communicate in this way. “For decades, we didn’t know what to look for, but with the growing scientific interest in vibrational communication, that’s all changing rapidly,” Caldwell says.






The female tree frog uses both airborne sounds and plant-borne vibrations to select between calls for potential mates. Credit: Dr. Michael Caldwell

This new focus on animal calls works through voice and vibration It can pave the way for significant progress in the study of signal has evolved. One potential implication highlighted by the Gettysburg College team is that “we may learn new things about audio cues that we thought we understood.” This is because both of It seems The vibratory components of bimodal audio signals are created together by the same organs. Therefore, the choice that acts on any component of the recall will necessarily shape the evolution of the other.

The red-eyed tree frog is one of the most photographed species on the planet, which makes these findings unexpected. “It’s just showing, we still have a lot to learn about animal behavior,” says Dr. Caldwell. “We hear animal sounds so often that we tune out most of them, but when we focus on looking at the world through the lens of a frog, the species more sensitive to vibrations than humans, it soon becomes clear that we were ignoring a good part of what they were saying to each other.”


A study showed that this frog has lungs that work like noise-canceling headphones


more information:
Michael S. Caldwell et al., Beyond Voice: Bimodal voice calls used in mate selection and aggression by red-eyed tree frogs, Journal of Experimental Biology (2022). DOI: 10.1242/jeb.244460

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Gettysburg College


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