November 4, 2015

Shake and quiver: Vibrational communication in animals

by Eric Dillalogue

Living underground, moles experience a world very different from our own. The dark, subterranean environment lacks the usual cues for direction, distance, or time, forcing moles to use other methods to perceive their habitat. Using senses like smell and touch, they can understand their immediate environment. But to understand a wider zone and to communicate with other animals hidden behind layers of earth, moles use vibrations. Species like the blind mole rat (genus Spalax) use a type of head drumming to send and receive information about their subterranean world. For example, they drum their heads against the tunnel walls to send messages to other mole rats in separate tunnels and they sense vibrations rebounded off of hidden obstacles as they dig. But subterranean animals are not the only one to communicate using vibrations; in fact, vibrational, or seismic, communication is an ancient and widespread phenomenon.

Examples of blind mole-rats using head drumming to communicate and navigate vibrationally. From Kimchi, T. & Terkel, J. (2002). Seeing and not seeing. Current Opinion in Neurobiology, 12(6), 728-734. doi:10.1016/S0959-4388(02)00381-1

To communicate vibrationally, animals act on a substrate, or medium, to send signal waves. Much like we communicate with sound by causing air molecules to vibrate back and forth in longitudinal waves, vibrational communication involves sending waveforms of energy through things like soils, plants, or webs. (To learn more about waves, see our Waves and Wave Motion module). To generate these waves, animals can use a variety of methods: drumming or pounding on the substrate, stridulation (rubbing together parts of the body), and tremulation (vibrating the entire body on a substrate).

Footfalls of large mammals, propagating along the surface of the earth as Rayleigh waves, are measurable in the ground at varying distances. Elephants can transmit seismic signals in the range of 32 km. ©O’Connell-Rodwell, C.E. (2007). Keeping an “ear” to the ground: Seismic communication in elephants. Physiology, 22(4), 287-294.

We most commonly see this type of communication in insects, though many types of animals use vibrations to both send and receive information. Sometimes these vibrational messages also include auditory elements, like termites that thump their heads on the nest to raise an alarm, sending vibrations to other termites and making a banging sound that we can hear. But often vibrational communication is, to humans at least, noiseless (think of the spider using vibrations to sense prey trapped in its web) and thus tends to go unnoticed. This may also be why vibrational communication methods have only recently been a focus of research. Discoveries include how certain social insects, like ants or bees, use vibrations to organize themselves for foraging, how elephants communicate over vast distances using seismic vibrations, and how some male frogs tremulate on plants to send aggressive signals to other males.

 

Not only are humans researching vibrational communication methods, but we are starting to implement some elements in our own communication devices. Some smartphones have a “haptic feedback” feature. Derived from a Greek word meaning “to touch,” haptic feedback, or haptics for short, involves sending information in the form of touch signals, including vibrations. If you’ve ever used the silent alarm on a phone or recognized you received a new message just by how your phone buzzed in your pocket, you’ve experienced a type of vibrational communication. To communicate directions, the Apple iWatch uses haptic pulses to tell the user when to turn while using the Maps feature. In the future, we may be able to send simple messages to one another that lack sound or text and only use vibrations to communicate information.

We live in a noisy, visually crowded world full of information, but there are other layers of information that go unnoticed every day. As Peggy Hill notes in her book Vibrational Communication in Animals,

Those who work outside the field of animal communication may justifiably be skeptical that humans could have missed stumbling on this phenomenon before, even if by accident, were it really as widespread and primary as we now argue. The answer, of course, is that we have encountered it, but we were not looking for it. …[A]n entire planet full of potential research subjects awaits our interest.

 

Resources:

– Vibrational Communication in Animals book by Peggy S. M. Hill (2008, Harvard University Press)

– Vibrational communication bibliography

– Topic: vibrational communication in animals (Map of Life)

– Good Vibrations: 7 Animals That Use Vibrations to Communicate (National Geographic)

– Video: Science Today – Extreme Communication, discussing how elephants communicate over long distances (CA Academy of Sciences)

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Written by

Eric Dillalogue holds a MS in Library and Information Science and a BA in English. He has worked in a variety of roles from service industry management, academic libraries, and grant administration. He has taught courses on information literacy, web research, and developmental reading. Eric joined the Visionlearning team as a project manager in 2014.

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