You might be hard-pressed to go for a walk outside without hearing the sounds of calling animals. Throughout the day, birds chatter backwards and forwards, so when night falls, frogs and insects call to guard territories also to attract potential mates. For many decades, biologists have studied these calls with great interest, removing major lessons concerning the evolution of animal displays and the processes of speciation. But there might be much more to animal calls than we’ve realized.
A fresh study appearing in the Journal of Experimental Biology by Dr. Michael Caldwell and student researchers at Gettysburg College demonstrates that the calls of red-eyed treefrogs don’t just send sounds through the air, but additionally send vibrations through the plants. Also, these plant vibrations change the message that other frogs receive in major ways. The researchers played sound and vibrations made by calling males to other red-eyed treefrogs surrounding a rainforest pond in Panama. They discovered that female frogs are over doubly likely to pick the calls of a potential partner if those calls include both sound and vibrations, and male frogs are more aggressive and show a larger selection of aggressive displays if they can have the vibrations generated by the calls of these rivals.
“This really changes how exactly we look at things,” says Caldwell. “If you want to understand how a call functions, we can not just consider the sound it creates anymore. We have to at the very least think about the roles that its associated vibrations play in obtaining the message across.”
Because vibrations are unavoidably excited in virtually any surface a calling animal is touching, the authors of the brand new study suggest chances are that lots of more species communicate using similar “bimodal acoustic calls” that function simultaneously through both airborne sound and plant-, ground-, or water-borne vibrations.
“There’s zero reason to suspect that bimodal acoustic calls are limited by red-eyed treefrogs. Actually, we realize they aren’t,” says Caldwell, who highlights that researchers at UCLA and the University of Texas are reporting similar results with distantly related frog species, and that elephants and many species of insect have already been proven to communicate in this manner. “For many years,” says Caldwell, “we just didn’t know very well what to consider, but with an evergrowing scientific fascination with vibrational communication, all that is rapidly changing.”
This new concentrate on animal calls as functioning through both sound and vibration could set the stage for major advances in the analysis of signal evolution. One potential implication highlighted by the team at Gettysburg College is that “we might even learn new reasons for having sound signals we thought we understood.” It is because both sound and the vibrational the different parts of bimodal acoustic signals are generated together by exactly the same organs. So, selection acting either call component may also necessarily shape the evolution of another.
The red-eyed treefrog is among the most photographed species on earth, making these findings even more unexpected. “It just would go to show, we still have too much to find out about animal behavior,” reports Dr. Caldwell. “We hear animal calls frequently that people tune a lot of them out, however when we create a point to consider the world from the perspective of a frog, species which are a lot more sensitive to vibrations than humans, it quickly becomes clear that people have already been overlooking a significant section of what they’re saying one to the other.”
More info: Michael S. Caldwell et al, Beyond sound: bimodal acoustic calls found in mate-choice and aggression by red-eyed treefrogs, Journal of Experimental Biology (2022). DOI: 10.1242/jeb.244460
Citation: Beyond sound: Red-eyed treefrogs use sound and vibration in demands mates and aggression (2022, September 14) retrieved 14 September 2022 from https://phys.org/news/2022-09-red-eyed-treefrogs-vibration-aggression.html
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