Late onset of hearing in the ferret.

Onset of hearing in the ferret was judged by simple behavioral, physiological and anatomical indices. The ear canals do not open until the end of the first postnatal month. This coincides with the appearance of a startle response to loud hand claps and the recording of acoustically activated neurons in the midbrain. The late onset of hearing in the ferret (around 32 days postnatal) contrasts with the cat (6 days) and the mouse (12 days).