[MARMAM] new publication: acoustic allometry in harbour seal pups

Andrea Ravignani andrea.ravignani at gmail.com
Mon May 29 23:36:56 PDT 2017

Dear colleagues,

We have just published a paper on the anatomical bases of acoustic allometry in harbour seal pups (i.e. which features of the vocal apparatus make a small pup sound small?), which might be of interest to some members of the list. The paper is open access and freely available at:  https://academic.oup.com/cz/article/3603549/How-small-could-a-pup-sound-The-physical-bases-of 

Ravignani, A., Gross, S., Garcia, M., Rubio-Garcia, A., & de Boer, B. (2017). How small could a pup sound? The physical bases of signalling body size in harbour seals. Current Zoology.

Vocal communication is a crucial aspect of animal behavior. The mechanism which most mammals use to vocalize relies on three anatomical components. First, air overpressure is generated inside the lower vocal tract. Second, as the airstream goes through the glottis, sound is produced via vocal fold vibration. Third, this sound is further filtered by the geometry and length of the upper vocal tract. Evidence from mammalian anatomy and bioacoustics suggests that some of these three components may covary with an animal’s body size. The framework provided by acoustic allometry suggests that, because vocal tract length (VTL) is more strongly constrained by the growth of the body than vocal fold length (VFL), VTL generates more reliable acoustic cues to an animal’s size. This hypothesis is often tested acoustically but rarely anatomically, especially in pinnipeds. Here, we test the anatomical bases of the acoustic allometry hypothesis in harbor seal pups Phoca vitulina. We dissected and measured vocal tract, vocal folds, and other anatomical features of 15 harbor seals post-mortem. We found that, while VTL correlates with body size, VFL does not. This suggests that, while body growth puts anatomical constraints on how vocalizations are filtered by harbor seals’ vocal tract, no such constraints appear to exist on vocal folds, at least during puppyhood. It is particularly interesting to find anatomical constraints on harbor seals’ vocal tracts, the same anatomical region partially enabling pups to produce individually distinctive vocalizations.

Thank you
Kind regards,

Andrea Ravignani
Veterinary & Research Dpt., Sealcentre Pieterburen
Max Planck Inst. for Psycholinguistics
AI-Lab, Vrije Universiteit Brussel

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