Elephants are very often seen on our safaris through Wilpattu and Yala National Park. Observing their habits and their way of communication with different sounds is always interesting. There are very specific sounds that can be heard and defined e.g. a loud growl of dissatisfaction, a unique high-tone shriek from young elephants and a low-tone rumble from elephant bulls in musk. What many people do not know, is that there are two other means that the large mammals use to communicate - Through low frequency sounds, which we humans cannot hear and through exchanging information by vibration in the ground.
What we cannot hear
The stunning revelation that elephants communicate over long distances using low-pitched sounds that are barely audible to humans, was first proposed by the ecologist Caitlin O'Connell-Rodwell and her team while they researched elephants in Etosha National Park in northern Namibia about 30 years ago. Their results suggest that elephants are specialists in the production of low frequency sound and in the use of long-distance communication.
Most of these sounds are not being perceived by humans, as the low-frequency rumbles are between one and two octaves below the lower limit of human hearing. The same rumbles enable elephants to communicate over very long distances (up to 2-3km!). The reason for that is the fact that low-frequency sound travels a lot farther than higher frequency sound.
Additionally, the elephants are very good in localizing these sounds, as it is suggested that their large inter-aural distance (the space between an animal's ears) helps to hear signals from very far away. Their well-developed system of sound-production and -reception makes them sending out signals to each other - a spectacle of nature that plays beyond the perception of our 5 senses, Find out about the meaning of various elephant noises in the article What Elephant Calls Mean: A User’s Guide.
The "Underground" World of Elephant Communication
Beside their secret acoustic communication, elephants also practise what we know as seismic communication. The low-frequency rumbles do not only travel by air as acoustic signal, they also flow as vibration through the ground. Therefore, the signal arrives a lot faster as seismic energy than as an acoustic signal delivered by air. Caitlin O'Connell-Rodwell and her team suggest that elephants are able to perceive the seismic information from the ground through their sensitive trunk, their bone structure, and a massive ossicle in their middle ear. Obviously, the seismic signals are not conscious messages sent from one elephant to another, but more undeliberated vibrations resulting from movements like running or charging, which resonate with the production of low-frequency acoustic sounds.
The seismic signals are mostly picked up as geographical information that update the receiving elephant about the location of other elephants. As a result, the seismic messages play a crucial role when it comes to their survival. As an example, elephants might recognize the location of predators, as they receive seismic signals coming from distress in another herd. The "underground" communication of elephants is such an intriguing topic and shows how miraculously our nature works. If you want to know more about it, please watch how Caitlin O'Connell-Rodwell presents further insights into the secret lives of elephants in her TED Talk.