Elephants use vibrations to make long-distance calls through the ground, and now scientists say the animals can tell who’s calling and may even screen their calls.
The low-frequency rumbles elephants make, some below the range of human hearing, travel through the ground as seismic waves that other elephants can feel and understand. In fact, they know if the caller is a neighbor or a stranger.
“It turns out that they can discriminate very well in the ground just as they can in the air, and that was a surprise,” said Stanford University behavioral ecologist Caitlin O’Connell-Rodwell. She led the study, which will appear in the Journal of the Acoustical Society of America in August.
O’Connell-Rodwell first discovered the ground communication three years ago after seeing elephants in Africa suddenly stand still, lean their weight forward onto their toes and rest their trunks on the ground without spreading their ears to listen. Often, other elephants would arrive soon afterward.
It turns out elephants have vibration-sensitive cells in their feet and trunks, which may act as receivers for the seismic waves.
O’Connell-Rodwell is studying just how much information the ground waves convey. By recording and playing back vibrations to elephants in Namibia, her team found the animals knew the difference between welcome calls and danger calls or a “let’s go” call.
In her newest experiment, she recorded call vibrations of elephants encountering lions in Namibia as well as the lion warning calls of Kenyan elephants. When she played the Namibian calls to elephants in Namibia, they responded as they would to an airborne alarm call – they stopped drinking, spread their ears to listen for danger, moved closer together and left the area sooner.
But when the Kenyan vibrations were played in Namibia, they were ignored.
“Elephants are so smart it seems like they’re gauging whether it’s important to respond or not,” she said.
She suspects the different reactions may have to do with trust: Elephants heed warnings from trustworthy neighbors but don’t waste energy on strangers who may be crying “wolf,” or in this case “lion.”
“Alarm calls are something an animal should pay attention to, but it’s time taken away from other behaviors,” said San Francisco State behavioral ecologist Jan Randall, who studies kangaroo rats that drum their feet on the ground to communicate. “Recognizing the caller and the context of the caller is important so animals aren’t responding to bogus calls.”
How specific this elephantine caller ID is, if they know it’s Dumbo or Babar calling, remains to be seen. But elephants can recognize a specific airborne voice, so O’Connell-Rodwell’s betting the same is true for the vibrations.
University of California at San Diego, Oakland Zoo and Stanford researchers took part in the study.
