Seismic communication signals in the blind mole-rat (Spalax ehrenbergi ): electrophysiological and behavioral evidence for their processing by the auditory system

Abstract

Based on morphological and behavioral findings we suggest that the seismic vibratory signals that blind mole-rats (Spalax ehrenbergi) use for intraspecific communication are picked up from the substrate by bone conduction and processed by the auditory system. An alternative hypothesis, raised by others, suggest that these signals are processed by the somatosensory system. We show here that brain stem and middle latency responses evoked by vibrations are similar to those evoked by high-intensity airborne clicks but are larger in their amplitudes, especially when the lower jaw is in close contact with the vibrating substrate. Bilateral deafening of the mole-rat or high-intensity masking noise almost completely eliminated these responses. Deafening also gradually reduced head-drumming behavior until its complete elimination about 4–6 weeks after surgery. Successive vibrations, at a rate of 0.5 vibrations/s, elicited prominent responses. At rates higher than 2 vibrations/s the amplitude of the brain stem response did not change, yet the middle latency response disappeared almost completely. It is concluded that the seismic signals that mole rats use for long distance communication are indeed processed primarily by the auditory system.