Elephants are the most famous "infrasonic" animals on land. Their low rumbles (roughly 5–14 Hz) lie at the edge of, and below, our hearing, but for elephants they are a full-fledged language that works where ordinary sound fails — over great distances and in dense forest.
A voice we can barely hear
In 1986 Katy Payne and colleagues first showed that the powerful "rumbles" of elephants contain an infrasonic component.1 The low frequency is not a quirk but an engineering solution: such waves attenuate weakly and bend around trees, so a herd can coordinate and search for mates kilometres away. Field playback experiments confirmed this: elephants responded to a herd-mate's call 2 km away, and the strongest calls are estimated to be audible at least 4 km away.5 The range depends strongly on the weather — in cool hours a near-surface temperature inversion acts as an acoustic lens and carries the sound even farther.6
They hear the ground with their feet
The rumble travels not only through the air but also as a seismic wave through the ground. Caitlin O'Connell-Rodwell showed that elephants pick up these vibrations through the pads of their feet and their trunk, and respond to them.2 A team from Oxford later learned to distinguish elephant behaviour from the seismic signal — whether they were walking, running or alarmed.3
An elephant has two channels of communication: air and earth. Sometimes they "speak" with their feet.
Playback — how scientists "reply" to elephants
To understand the elephants' language, researchers (for example, Joyce Poole's ElephantVoices project) use playback experiments: a recorded rumble is played back through a powerful subwoofer and the reaction is observed. This is how it was found that elephants distinguish the "voices" of relatives, strangers and even dangerous sounds. It is both a tool and an ethical responsibility — one must intervene in animal communication carefully.
For the forest, where visual counting is impossible, acoustics has become the main method. The Elephant Listening Project (Cornell) has spent many years listening to Africa's forest elephants with arrays of microphones, estimating numbers and detecting poaching.4
- On cool nights an elephant's call carries farther: a cold near-surface layer of air acts as an acoustic lens.
- Elephants "listen to the ground" with the pads of their feet and their trunk — they contain vibration-sensitive Pacinian corpuscles.
- From acoustics, scientists distinguish the individual "voices" of forest elephants — almost like fingerprints.
- Infrasound is used by more than elephants: tigers roar with components below 20 Hz (von Muggenthaler, 2000).
- Hippos communicate simultaneously in the air and underwater (Barklow, 2004).
- Alligators "sing" so low that the water above their backs literally dances (Reber et al., 2017).
Animals do react to the infrasound of storms and distant events — but a rigorous review found no reproducible signal for the popular idea that "animals predict earthquakes" (Woith et al., 2018). It is more honest to say so plainly — and it only strengthens trust in the rest of the facts.
HERD grew out of a love for elephants and pain on their behalf. The same powerful low-frequency emitter needed for playback experiments is part of our laboratory. More about our R&D →
Sources for this article
- peer-reviewed Payne K.B., Langbauer W.R., Thomas E.M. (1986). Infrasonic calls of the Asian elephant. Behav. Ecol. Sociobiol. 18(4). springer.com
- peer-reviewed O'Connell-Rodwell C.E. (2007). Keeping an 'ear' to the ground: seismic communication in elephants. Physiology 22(4). physiology.org
- peer-reviewed Mortimer B. et al. (2018). Classifying elephant behaviour through seismic vibrations. Current Biology 28(4). cell.com
- organization Elephant Listening Project, Cornell University. elephantlisteningproject.org
- peer-reviewed Langbauer W.R., Payne K.B., Charif R.A., Rapaport L., Osborn F. (1991). African elephants respond to distant playbacks of low-frequency conspecific calls. J. Exp. Biol. 157. journals.biologists.com
- peer-reviewed Garstang M. et al. (2005). The daily cycle of low-frequency elephant calls and near-surface atmospheric conditions. Earth Interactions 9(14). journals.ametsoc.org
- peer-reviewed von Muggenthaler E. (2000). Infrasonic and low-frequency vocalizations from Siberian and Bengal tigers. JASA 108(5). doi.org
- peer-reviewed Barklow W.E. (2004). Low-frequency sounds and amphibious communication in Hippopotamus amphibius. JASA 115. doi.org
- peer-reviewed Reber S.A. et al. (2017). Formants provide honest acoustic cues to body size in American alligators. Sci. Rep. 7. doi.org
- peer-reviewedrebuttal Woith H., Petersen G.M., Hainzl S., Dahm T. (2018). Can animals predict earthquakes? BSSA 108(3A). doi.org