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 [email protected]. 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 [email protected]
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