Elephants can talk to each other from 6km away
Making noises through their trunks isn’t the only way elephants communicate. Dr Beth Mortimer of Oxford University reveals their secret language
What noises does an elephant make?
In terms of purposeful signals, those are made by vocalisations – using their vocal cords the same way that we do when we’re talking. People have heard of ‘trumpets’, but elephants have a whole range of vocalisations. The ones that go through the ground are known as ‘rumbles’ because they’re infrasonic vibrations – ultrasound is super-high frequency; infrasound is super-low frequency, under 20 Hertz. We can’t hear this type of vocalisation but, if you’re close enough to an elephant, you can feel it. It’s like a super-loud bass. We don’t know for sure how the elephants detect ground vibrations, but it’s either through sensors under their feet – similar to those we have in our skin – or through the feet, so the vibration travels up the leg bones to the middle ear, known as a bone-conduction method.
What do the rumbles mean?
There are alarm rumbles, greeting rumbles, ‘let’s go’ rumbles… There’s different information content depending on the social situation. The interesting thing about rumbles is that part of the vibration goes through the air, but it goes through the ground as well and not much is known about what role the physical environment plays on that.
How did you detect rumbles?
For the elephant project, we went into the field in Kenya and used geophones, which are basically microphones for the ground – the same equipment used to monitor earthquakes and processes through the Earth. So we were taking well-established techniques and approaches used in seismology, but applying them to elephant behaviour and conservation monitoring. We were recording vibrations to make computer models and were interested in what effect the different types of soils and landscapes would have.
How far do the signals travel?
There isn’t much experimental data, but based on our models, in favourable conditions – low background [noise] and on a sandy terrain – we think it’s six kilometres. Certainly over the kilometre range. So when they can’t see other elephants or use other signals to detect them, they might be able to use vibrations. They’ve got the potential for long-distance communication. You play the recordings back to elephants, we
call this seismic playback, and they only respond to calls from elephants they know. They can even discriminate the identity of the sender.
Why are vibrations useful to study?
If you put ground-based recorders in remote locations, then you can monitor the movements and identity of different types of wildlife in that habitat. Because elephants only really run if they’re in distress, we might be able to pick up this ‘panic running’, which would be useful information of whether there’s a poaching threat, for example. Our next plans are to look at how sensitive the elephants are to these vibrations.