European Mole - Hearing

Hearing

In mammals the cues for hearing are usually based on inter-aural intensity differences, which occur as a result of the diffraction of a progressive sound wave by the head and pinna. They could also be based on inter-aural time differences that are present because of the distance between their two ears. Moles have no pinna so they are thought to hear at low frequencies. In addition to this, their inner ear is unusual for that of a mammal due to the large trabeculation of the posterior ventral skull between the ears. The tympana of the ear lays almost horizontal and the manubrial tips are separated by a distance of 8 mm. The results of several studies confirms that there is good transmission through European mole’s head for a range of low frequencies. Because of this it is expected that there will be acoustic interaction at each tympanic membrane. The results of the study also suggest that the ears of this mole act as balanced, pressure-difference receivers. This system has never been suggested for a mammal in the past, but other reptiles, amphibia, birds, and crickets have been shown to have a direct air pathway between the tympana.