Elephants can hear through their feet
Elephants have a great sense of hearing and can send vocalizations a long distance. The species makes a variety of sounds, including snorts, roars, cries and more. But they also specialize in rumbles and are able to pick up sounds in a more unusual way.
While trumpeting may be heard a good distance away, elephants can also communicate in a low rumble that can travel as far as 6 miles, and what's more, the elephant receiving the call picks it up through its feet.
Caitlin O'Connell-Rodwell, a biologist at Stanford University in Palo Alto, California, found that the vocalizations and foot stomps of elephants resonate at a frequency other elephants can detect through the ground. Enlarged ear bones as well as sensitive nerve endings in their feet and trunks allow elephants to pick up these "underground" or infrasonic messages.
Stanford News reported in 2001, "The researchers wanted to find out if elephants would respond to recordings played through the ground, so they installed seismic transmitters at a tourist facility in Zimbabwe where eight trained, young elephants were housed."
"We think they're sensing these underground vibrations through their feet," said O'Connell-Rodwell. "Seismic waves could travel from their toenails to the ear via bone conduction, or through somatosensory receptors in the foot similar to ones found in the trunk. We think it may be a combination of both."
So when an elephant stomps when agitated, there's a purpose greater than just warning those in the immediate area — the elephant may also be warning other elephants many miles away. And when an elephant rumbles a call, it could be intended for family members far out of sight.
The ability to detect such seismic vibrations also helps elephants survive. National Geographic reported in 2004 that long-distance communication can help keep family members in touch even when they are spread over great distances to find food and water in times of scarcity. It can also provide other cues to danger.
"It's believed that elephants can hear storms as much as 100 to 150 miles (160 to 240 kilometers) away," Michael Garstang, a meteorologist at the University of Virginia, Charlottesville, told National Geographic. "When culling was being done in some of the parks, the elephants could clearly detect and identify the thump-thump-thump sound of the helicopter blades from 80 to 90 miles (130 to 140 kilometers) away, identify it as danger, and take off in the opposite direction."
The video below from KQED's Deep Look series shows elephants at the Etosha National Park in Namibia using their feet to "exchange information by emitting low-frequency sounds that travel dozens of miles under the ground on the savannah."