It’s widely known elephants use a range of communicative trumpets, purrs and rumbles, but they also use sounds we can’t even hear – and now we know what they mean.

Elephants are highly social, intelligent animals. They live in family groups made up of related females, and just like us they form deep family bonds. The herd is led by the oldest and often largest female, called a matriarch. When a calf is born, it is raised and protected by the whole matriarchal herd.

Within the family group, individuals of all ages greet, and maintain bonding, by touching their trunk tips to each other’s bodies, and through both scent and sound when they are separated.

Elephants have acute hearing and communicate via a wide variety of sounds. Many different calls and rumbles audible to the human ear have been identified, each with their own meaning and intention as understood by members of the herd.

But more than this, elephants also use a range of infrasonic vocalisations – sounds which extend down to 5Hz, well below the 20Hz frequency which is the limit of human hearing.

Elephants use these low-frequency sounds as a form of long-distance communication as they can travel further without being absorbed or reflected by the environment.

These forms of elephant tele-communication are thought to carry up to 7km through dense forest and much further over open savannah.

It is believed that this is how social groups coordinate their patterns of movement for weeks at a time even when physically separated from each other.

The key apparatus allowing elephants to communicate so efficiently is their trunk.

Elephants make sounds in much the same way as we do, using their vocal folds to generate the source frequency and then modifying the sound’s structure by filtering it with the shape of their mouth and the nasal passages. But unlike us elephants can also modify the sound using their long trunk.

The trunk gives elephants an extra six feet of sound modification allowing them to concentrate sound energy in different parts of the call structure and achieve lower frequencies. Nasal rumbles are therefore thought to be particularly important for long distance communication.

We also know that when elephants eat, they are constantly purring.

This signals to the group that all is well. But when an individual detects danger, it stops purring and the sudden silence alerts the others, who also fall silent and become alert to the possible threat.

Most excitingly, we can actually understand some forms of elephant communication.

Elephants also have specific alarm calls which provide other elephants with information about the nature of potential dangers. Researchers have identified an alarm call for humans in Kenyan elephants. These herds produce a specific low rumbling sound when they hear local tribespeople approaching and this signals to the group that it’s time to move away.

We know this sound is specific to humans as different calls have been identified for other species.

Elephants are not fond of bees and when the specific alarm for bees is bees is made, the elephants don’t move away as they do for humans, but instead shake their heads.

To our human ears these alarm calls sound the same, as they are made at such low frequencies that it is difficult for us to detect the differences. But to an elephant’s large, floppy ears they make perfect sense and are the basis of harmonious elephant societies.

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