Vibrational Communication in Elephants: A Case for Bone Conduction

Abstract

We present new physiological data on bone conduction hearing from cadaveric temporal bone ears of an elephant. We discuss the results in the context of the elephant's ability to detect and interpret ground-borne vibrations as signals and compare with similar measurements in a human cadaveric temporal bone ear. Large ossicles are potentially indicative of superior bone conduction hearing, and elephant ossicles are the largest among terrestrial mammals. Using 3D laser vibrometry, we measured stapes velocity in each x, y, z planes and the promontory velocity to determine relative velocity as an indication of vibrational input to the cochlea via the footplate. Since elephant ossicles are at least seven times the mass of human ossicles, we compare the sensitivity of both species to vibrations in the frequency range of 8-10,000 Hz and report that elephants have up to an order of magnitude greater sensitivity below 200 Hz, indicating a heightened sensitivity to bone conduction hearing in comparison to humans.