L. Aitkin et al., DEVELOPMENT OF HEARING AND VOCALIZATION IN A MARSUPIAL, THE NORTHERN QUOLL, DASYURUS-HALLUCATUS, The Journal of experimental zoology, 276(6), 1996, pp. 394-402
The development of hearing was studied in the Northern Quoll, a noctur
nal marsupial carnivore whose young are born into a pouch in an immatu
re state after about 21 days in utero. Startle responses to noise burs
ts of 105 dB sound pressure level first appeared at 60 days after arri
val in the pouch, but only to occasional stimuli; forelimb rather than
whole body twitches were evoked. The latter were elicited regularly a
t 67 days onward. Auditory brainstem response (ABR) audiograms were me
asured during the period when startle responses first appeared. At 68
days responses were elicited between 1 and 16 kHz with thresholds in e
xcess of 55 dB. At 81-88 days responses occurred over the adult range
at lower thresholds than observed in the adult. The waveform of the AB
R increased in complexity and decreased in latency during development.
Pouch-young emitted acoustically well-defined isolation calls when se
parated from their mothers. Fourier analysis of these calls revealed p
eak energy at 8-11 kHz irrespective of the sex of the pouch-young. The
isolation call first became evident at about 35 days, when the young
were deliberately removed from the nipple, and ceased being emitted be
yond about 80 days, some 5 or so days after the eyes open, when the yo
ung leave the pouch for substantial amounts of time. The spectrum of t
he call was similar at all ages within this 45 day period, and its pea
k frequency correlated closely with the best frequency in the adult qu
oll's ABR audiogram. At approximately 80 days of age the calls develop
ed major low frequency components, similar to those measured in adult
vocalizations, and the contributions of frequencies between 8-11 kHz w
aned in importance.The results indicate that the onset of hearing in q
uells occurs at a relatively early time in the course of their develop
ment, but prior to this time the pouch-young emit characteristic isola
tion calls easily detectable by the mother. (C) 1996 Wiley-Liss, Inc.