[MARMAM] New Publication: Support for the beam focusing hypothesis in the false killer whale

Laura Kloepper lkloepper at saintmarys.edu
Fri Aug 7 09:59:24 PDT 2015


Dear Colleagues,

We are pleased to announce the publication of the following in The Journal
of Experimental Biology:

"Support for the beam focusing hypothesis in the false killer whale"

by Laura N. Kloepper, John R. Buck, Adam B. Smith, Alexander Ya. Supin,
Jason E. Gaudette and Paul E. Nachtigall, J Exp Biol, 218, 2455-2462.

This publication is a follow-up to our 2012 JEB paper in which we
demonstrated active focusing in the false killer whale, and provides
further support to the focusing hypothesis we proposed in that paper.

In our 2012 paper we demonstrated the false killer whale narrowed its sonar
beam when the target was further away, and we are pleased to see that many
of our colleagues have recently documented this in other odontocete
species. This new paper in JEB provides further insight into this focusing
hypothesis, demonstrating that the sonar beam has a narrower beamwidth and
higher intensity at distance that what would be predicted by spreading
losses alone.

The abstract is listed below, but for pdf requests please contact
lkloepper at saintmarys.edu.

Abstract: The odontocete sound production system is complex and composed of
tissues, air sacs and a fatty melon. Previous studies suggested that the
emitted sonar beam might be actively focused, narrowing depending on target
distance. In this study, we further tested this beam focusing hypothesis in
a false killer whale. Using three linear arrays of hydrophones, we recorded
the same emitted click at 2, 4 and 7 m distance and calculated the
beamwidth, intensity, center frequency and bandwidth as recorded on each
array at every distance. If the whale did not focus her beam, acoustics
predicts the intensity would decay with range as a function of spherical
spreading and the angular beamwidth would remain constant. On the contrary,
our results show that as the distance from the whale to the array
increases, the beamwidth is narrower and the received click intensity is
higher than that predicted by a spherical spreading function. Each of these
measurements is consistent with the animal focusing her beam on a target at
a given range. These results support the hypothesis that the false killer
whale is ‘focusing’ its sonar beam, producing a narrower and more intense
signal than that predicted by spherical spreading.

-- 
Dr. Laura Kloepper
Assistant Professor
Department of Biology
Saint Mary's College
Notre Dame, IN 46556
lkloepper at saintmarys.edu
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