Science reporter, BBC News, Chicago
A bull elephant in Namibia responds to a mating call
It's one of the most fabled talents in the animal world – elephants' ability to "talk" via rumbles in the earth.
Now zoologists in Namibia are trying to harness these seismic social calls - to lure rampaging males back to safety.
They played the low rumble of a female on heat to bulls in must (a state of sexual readiness), who turned and headed for the vibration source.
The tool could help save elephants from Etosha National Park from the risk of violent conflicts with farmers.
The trials are being led by Dr Caitlin O'Connell-Rodwell, of Stanford University.
She told the American Association for the Advancement of Science conference in Chicago that park rangers are "very excited" about the prospect of using the technique to protect the endangered animals.
"The bulls in must were very responsive. We have shown that we can set the elephants on a very specific trajectory," said Dr O'Connell-Rodwell.
"At the watering hole, we waited for them to arrive, and then used the calls to set them on one path, and then turn them back round again.
"You see the male in the video pressing his trunk against the ground. He's on a mission – he's looking for that female in oestrus," she said.
"The response was intense and so directed. We were not expecting such intensity.
"We suggest this could be used as a tool by the park rangers – to help the elephants to stay out of trouble.
"The Namibian Environment Ministry is very interested," Dr O'Connell-Rodwell added.
Elephants are renowned for their ability to detect vibrations through the ground at great distances.
These include the mating calls of females who are in oestrus – or on heat, a phase which only occurs every five years.
Dr O'Connell-Rodwell wondered if this could be harnessed to lure stray elephants back into Etosha National Parks, where they are protected.
There have been violent conflicts between elephants and farmers in many regions of Africa.
Elephants damage crops, break water installations and may end up being shot.
"It's very difficult to get them back into the park. Someone ends up getting hurt," said Dr O'Connell-Rodwell
"I have been studying elephant behaviour for 15 years and it has always been in the back of my mind – could we use this behaviour to reduce the crisis which is going on out there?"
"Nobody has really thought of using these calls in this way before," she said.
To test her idea, Dr O'Connell-Rodwell used a speaker buried in the ground to play the oestrus call to males.
The call is a low rumble, barely audible to humans, as it falls at the lower limit of our hearing frequency range.
The researchers played the call to 26 bull male elephants in three classes: adults who were in must; adults who were not; and sub-adult males.
The bulls in must were "particularly responsive".
How far away the elephants can sense vibrations is still a mystery, says Dr O'Connell-Rodwell.
The sound travels through their fore-legs and up through their bones to the middle ear bone.
While they can hear mating calls at distances of up to 10km (six miles), they may be able to sense the vibrations even further.
"In this experiment, we only played the calls at 500m, but we think it would work at much further distances. Males have been shown to respond at up to two km," said Dr O'Connell-Rodwell.
She admitted that 500m "doesn't sound like a lot, until you try to corral a bull elephant in must.
"Even if the rangers can move an elephant bit by bit - 500m, and then another 500m, and then another, they can make a big difference," she said.
"We have modelled this in a quiet area of a national park, but we would like to try it in a noisier environment.
"There is evidence that elephants are being increasingly disturbed by noise," Dr O'Connell-Rodwell said.
"We don't know how much they rely on vibrations, as compared to audible sounds."
The research was funded by Utopia Scientific, a non-profit organisation.