Hearing in African Pygmy Hedgehogs (Atelerix albiventris): Audiogram, Sound Localization, and Ear Anatomy

Abstract:

Abstract The behavioral audiogram and sound localization performance, together with the middle and inner ear anatomy, were examined in African pygmy hedgehogs Atelerix albiventris. Their auditory sensitivity at 60 dB SPL extended from 2 kHz-46 kHz, revealing a relatively narrow hearing range of 4.6 octaves, with a best sensitivity of 21 dB at 8 kHz. Their noise-localization acuity around the midline (minimum audible angle) was 14°, matching the mean of terrestrial mammals. The African pygmy hedgehog was not able to localize low-frequency pure tones or a 3-kHz amplitude-modulated tone when forced to rely on the interaural phase-difference cue, a trait shared by at least nine other mammals. The middle ear of Atelerix has a primitive configuration including an unfused ectotympanic, a substantial pars flaccida, a synostosed malleo-tympanic articulation and a ‘microtype’ malleus. A similar malleus morphology, including a stiff articulation with the skull, is a consistent feature of other mammals that do not hear frequencies below 400 Hz. The hearing of A. albiventris is discussed relative to the broad range of hearing and sound localization abilities found in mammals.