Are seismic communication signals transmitted by bone conduction in the blind mole rat?

The anatomy of the middle ear of the blind mole rat, a subterranean rodent that uses seismic signals for long distance communication, is described qualitatively and quantitatively. The ossicular chain is of the parallel type with a lever arms ratio of 0.55 and an effective areal ratio of stapedial footplate to eardrum of 0.09. Assuming an ideal mechanical transform, the calculated fraction of acoustical energy theoretically transmitted to the cochlea, indicate low efficiency for airborne sounds. This is in accordance with the relatively high electrophysiological and behavioral threshold, shown previously. We suggest that a unique morphology of the middle ear and of the articulation between the lower jaw and the skull, as well as a peculiar 'jaw listening behavior' enable seismic vibrations to be transmitted to the inner ear mainly by bone conduction, thereby compensating for the limitation in receiving airborne signals.