HEARING IN THE MARSUPIAL MONODELPHIS-DOMESTICA AS DETERMINED BY AUDITORY-EVOKED BRAIN-STEM RESPONSES

The audiogram of the marsupial Monodelphis domestica was determined by measuring brainstem auditory-evoked potentials in response to pure-to ne stimuli of 2-90 kHz. The frequency range at 60 dB SPL comprises fre quencies between about 2.3 and 63 kHz. The best frequency range with a verage thresholds of 3 dB SPL in young adults (3 months old) is betwee n 12 and 16 kHz. In older animals, thresholds are higher. The overall shape and frequency range of the audiogram and the absolute thresholds indicate that hearing in this small marsupial is typically mammalian and cannot be considered primitive.