Simone Lange, Hynek Burda, Regina E. Wegner, Philip Dammann, Sabine Begall and
Mathias Kawalika
Living in a ?stethoscope?: burrow-acoustics
promote auditory specializations in subterranean rodents
Naturwissenschaften
Volume 94, Number 2 / February, 2007
pp 134 - 138
Abstract Subterranean mammals rely to a great extent on audition for
communication and to be alerted to danger. The only hitherto published report
on burrow acoustics revealed that in tunnels of blind mole-rats (Spalax
ehrenbergi), airborne sounds of 440 Hz propagated best whereas lower and higher
frequencies were effectively attenuated. Morpho-functional analyses classify
the ear of subterranean mammals as a low-sensitivity and low-frequency device.
Concordantly, hearing is characterized by low sensitivity and a restricted
frequency range tuned to low frequencies (0.5?4 kHz). Some authors considered
the restricted hearing in subterranean mammals vestigial and degenerate due to
under-stimulation. In contrast to this view stand a rich (mostly low-frequency)
vocal repertoire and progressive structural specializations of the middle and
inner ear. Thus, other authors considered these hearing characteristics
adaptive. To test the hypothesis that acoustical environment in burrows of
different species of subterranean mammals is similar, we measured sound
attenuation in burrows of Fukomys mole-rats (formerly known as Cryptomys, cf.
Kock et al. 2006) of two differently sized species at different locations in
Zambia. We show that in these burrows, low-frequency sounds (200?800 Hz) are
not only least attenuated but also their amplitude may be amplified like in a
stethoscope (up to two times over 1 m). We suggest that hearing sensitivity has
decreased during evolution of subterranean mammals to avoid over-stimulation of
the ear in their natural environment.
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Dr. Alan McElligott
The School of Biology
Biology Building
The University of Nottingham
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Nottingham NG7 2RD
UK
Tel + 44 (0) 115 951 3231
Fax + 44 (0) 115 951 3251
http://www.nottingham.ac.uk/biology/
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