Could putting vibrations into the ground be a way to keep elephants from coming into conflict with humans?
Already, attempts have been made to scare the animals away from villages using their own very low-frequency alarm calls – with partial success.
Now scientists are studying whether even better results could be obtained if this sound in the air is accompanied also by a seismic signal underfoot.
The work is being led by Prof Sue Webb from Wits University in Johannesburg.
The ultimate goal she said was to try to find a means of keeping everyone safe – both humans and elephants.
“Elephants can be incredibly destructive, especially with people’s farmlands,” she told BBC News.
“They come on to the farmland and they eat the crops and they push over the houses, and even kill people sometimes.
“So this is a huge problem in some rural parts of Africa and the issue is to try to find a way to keep the elephants out of human areas.”
Prof Webb was speaking at the Fall Meeting of the American Geophysical Union – the world’s largest annual gathering of Earth scientists.
Various ideas have been proposed for scaring elephants away from populated areas.
Putting beehives near crop fields is one solution: elephants hate being stung on their trunks.
Another method that has drawn considerable attention in recent years is the use of infrasound.
Elephants can communicate at auditory frequencies that are well below what humans are capable of hearing.
This noise can travel large distances, and so efforts have been made to record the animals’ alarm calls and then play them back in the infrasonic band to keep herds as far away as possible.
“The problem is that elephants are incredibly smart, and they soon figure out when things are fake,” explained Prof Webb.
“If you’re just playing back the infrasound, they’ll work out that it’s not the real signal and they learn that it’s not something they need to be afraid of.”
Prof Webb’s hypothesis is that a critical element could be missing from this approach: seismic signals.
She is working on the assumption that elephants communicate both through the air and through the ground.
It is possible the elephants know a fake infrasonic call when they do not sense a seismic signal at the same time.
“I strongly suspect it is a coupled signal between the infrasound and the seismic, but it’s not clear to me yet just how big the seismic signal is, and how important it is in all cases.”
An effective means is needed to keep elephants from coming into conflict with humans
To investigate, Prof Webb is using the trained animals of the Adventures With Elephants organisation, just north of Johannesburg.
These creatures will rumble on command – just as dog will bark when asked to “speak” by a handler bearing a treat.
Prof Webb’s team puts geophones on the ground to record and characterise the rumbles’ seismic signature in the earth.
It is early days in the experiments, but it is already clear that there is a sizeable signal to detect and that it can travel a considerable distance.
Of course, the rumbles coming from Prof Webb’s elephants are just the murmurings of greedy animals.
A future step would be to record the seismic signals associated with real elephant alarm calls.
“Eventually, the idea is to have something cheap and mobile that can be deployed quickly to scare the elephants away.
“It may just be a speaker that you have to couple with the ground in a more effective way than has been done in the past.”
The project was inspired by elephant researcher and writer Bob Preller.