Reuter and Nummela's recent letter hypothesized that elephants may sense ground vibrations by bone conduction and use of the massive ossicles of their middle ears. Their inner ears also are specialized for low frequencies, having reverted to a reptilian-like cochlear structure that may facilitate detection of seismic signals. Although bone conduction could be used for detection of seismic signals, mechanoreceptors with neural transmission are also a possibility. For localization of 20-Hz signals, the pinnae are limited given the large wavelengths involved, unless higher harmonics are reliably present.
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