Researchers observed treefrogs on their perches pressing and contracting their bodies in order to create a vibrational signal that is sent through the plant to other nearby frogs.
Credit: Michael S. Caldwell
Researchers observed treefrogs on their perches pressing and contracting their bodies in order to create a vibrational signal that is sent through the plant to other nearby frogs.
Credit: Michael S. Caldwell
SYDNEY: Whales use sonar, bats use echolocation and treefrogs, it seems, communicate through vibration.
That's according to an international group of herpetologists, who report in Current Biology finding male red-eyed treefrogs in Panama using vibrations in displays of aggression.
"While there has been a lot of work focusing on how these animals communicate with sound and visual signals, our study is the first experimental demonstration that tree-dwelling vertebrates can communicate using … vibrations," said Michael Caldwell from Boston University and lead author of the paper.
Vibrational signals
The researchers observed treefrogs on their perches pressing and contracting their bodies in order to create a vibrational signal that is sent through the plant to other nearby frogs, communicating territorial aggression.
Other arboreal species could also be communicating through vibrations, including other frog species, birds and even primates, the researchers noted.
The findings could open up a new direction in animal communications research, inspiring "other researchers to stop and think about how important vibrations could be for the species that they study," said Caldwell.
While vibration sensitivity has been observed in other animals such as the veiled chameleon and the South Asian common treefrog, responses to those vibrations have never before been studied as a means of communication.
Infrared light
Studies of elephant communication have shown that vibrations created by these mammoth creatures stomping their feet against the ground creates seismic signals that can be interpreted by other elephants.
The researchers decided to look for the use of vibrations in adults after detecting vibrations initiated by red-eyed treefrogs at the embryo stage. Because the embryos appear to sense attacks of egg predators, the researchers wondered if aggressive displays by adults could also be reactions to vibrational signals.
The team observed frog's behaviours beside a rainforest pond using infrared light so as not to disturb them; "just like humans, the frogs don't see infrared; so, as far as they are concerned, they are in the dark," said Caldwell.
This was the first time researchers have observed these frogs appearing to tremulate - to shake all or part of their body - in order to create a vibrational signal.
Artificial stimuli
Using a robotic frog and a electronic shaker, the researchers were able to record and mimic the vibrations caused by the frogs, and test how real frogs reacted to the artificial stimuli.
They found that dominant males tremulate more often and for longer amounts of time than those of submissive males.
Smaller males, and males in closely matched aggressive contests, tend to have higher frequency tremulations. This suggests that vibrations carry signals about the size and aggressive intent of the tremulating frog.
"You can feel them [vibrations] with your hand if the shaking frog is nearby," said Caldwell. The frogs, however, can feel the vibrations as far as two metres away. Caldwell suggests that the vibrations may be a creative way of avoiding predators, like bats, that use sound to find their prey.
