REPTILE EARS AND MAMMALIAN EARS: HEARING WITHOUT A TRAVELLING WAVE

This paper takes a closer look at the functional similarities between reptile ears and mammalian ears. The ears of the first class of animal are generally acknowledged to lack travelling waves – because the sensing cells sit upon a stiff support – whereas the ears of the second group are commonly thought to act differently, having hair cells arranged upon a compliant basilar membrane that moves under the action of a travelling wave (created by a pressure difference across the membrane) so that the wave bends the cells’ stereocilia. However, recent work suggests that the mammalian case can be explained without reliance upon a travelling wave as a causal stimulus and that the responses observed can be interpreted as local resonances driven by a fast pressure wave. In this light, reptiles and mammals may have more in common than currently appreciated – they might both be forced resonant systems – and this paper explores such a possibility.