Elecomm
September 21, 2009
We hear sounds waves that have traveled through the air or the water or a string in the case of a child’s homemade cup phone. But vibrations can also travel through the ground. While we, as humans, may not be able to perceive, nevermind interpret, these subtle vibrations, there is at least one species that can: elephants.
Indeed, elephants produce and ‘hear’ low frequency vocalizations (below what the human ear can perceive) that can travel very long distances through the ground. Dr. Caitlin O’Connell-Rodwell of Stanford identified this so-called seismic communication when a group of elephants she was observing simultaneously paused during a midday stroll and pressed their front feet or trunks into the ground. This bizarre behavior turned out to be the pachyderm version of perking one’s ears.
Based on O’Connell-Rodwell’s experiments, it seems that elephants can not only perceive these seismic signals, but they can interpret them as well. One signal produced by the elephants, for example, appeared to warn of hunting lions in the area.
Elephants are believed to process these signals through mechanoreceptors known as Pacinian corpuscles found in their feet and their trunk. They also seem to be detecting the signal through their toenails, which transmits the vibrations through the bones of their legs and body all the way to the bones of the middle ear, which perceive the noise. This pathway is heightened when they close their middle ear canal, which allows pressure to build up in the middle ear and enhances the bone-conducted signal and shuts out any airborne noises.
Click here to hear a podcast of The American Physiological Society with O’Connell-Rodwell about her studies of elephant communication, or what Christine Guilfoy calls ‘elecomm.’
