[MARMAM] new article - Risso's dolphin hearing

Aran Mooney amooney at whoi.edu
Thu May 28 03:14:48 PDT 2015


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,  amooney at 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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