We are pleased to announce the publication of a new article on hearing
pathways in the Risso's dolphin, with comparison's to other species.
Mooney, TA, Yan, J, Yu, U, Ketten, DR, and Jen, IF. 2015. Hearing
abilities and sound reception of broadband sounds in an adult Risso’s
dolphin (Grampus griseus). Journal of Comparative Physiology A. doi:
10.1007/s00359-015-1011-x
Copies of the article may be found in the Online First Section at the J.
of Comparative Physiology:
http://link.springer.com/article/10.1007/s00359-015-1011-x
or by contacting Aran Mooney, amoo...@whoi.edu
Abstract
While odontocetes do not have an external pinna that guides sound
to the middle ear, they are considered to receive sound through
specialized regions of the head and lower jaw. Yet odontocetes differ in
the shape of the lower jaw suggesting that hearing pathways may vary
between species, potentially influencing hearing directionality and
noise impacts. This work measured the audiogram and received sensitivity
of a Risso’s dolphin (Grampus griseus) in an effort to comparatively
examine how this species receives sound. Jaw hearing thresholds were
lowest (most sensitive) at two locations along the anterior, midline
region of the lower jaw (the lower jaw tip and anterior part of the
throat). Responses were similarly low along a more posterior region of
the lower mandible, considered the area of best hearing in bottlenose
dolphins. Left and right side differences were also noted suggesting
possible left-right asymmetries in sound reception or differences in ear
sensitivities. The results indicate best hearing pathways may vary
between the Risso’s dolphin and other odontocetes measured. This animal
received sound well, supporting a proposed throat pathway. For Risso’s
dolphins in particular, good ventral hearing would support their
acoustic ecology by facilitating echo-detection from their proposed
downward oriented echolocation beam.
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