Dear All, This recent paper sheds new light on how toothed whales use their nose to produce high powered echolocation clicks. Requests for reprints can be directed to peter.madsen@biology.au.dk Single source sound production and dynamic beam formation in echolocating harbour porpoises (Phocoena phocoena) P. T. Madsen*, D. Wisniewska and K. Beedholm Zoophysiology, Department of Biological Sciences, Aarhus University, Build 1131, 8000 Aarhus C, Denmark *Author for correspondence (peter.madsen@biology.au.dk) Accepted 14 June 2010 The Journal of Experimental Biology 213, 3105-3110 C 2010. Published by The Company of Biologists Ltd doi:10.1242/jeb.044420 SUMMARY Echolocating toothed whales produce high-powered clicks by pneumatic actuation of phonic lips in their nasal complexes. All non-physeteroid toothed whales have two pairs of phonic lips allowing many of these species to produce both whistles and clicks at the same time. That has led to the hypothesis that toothed whales can increase the power outputs and bandwidths of clicks, and enable fast clicking and beam steering by acutely timed actuation of both phonic lip pairs simultaneously. Here we test that hypothesis by applying suction cup hydrophones on the sound-producing nasal complexes of three echolocating porpoises (Phocoena phocoena) with symmetrical pairs of phonic lips. Using time of arrival differences on three hydrophones, we show that all recorded clicks from these three porpoises are produced by the right pair of phonic lips with no evidence of simultaneous or independent actuation of the left pair. It is demonstrated that porpoises, despite actuation of only one sound source, can change their output and sound beam probably through conformation changes in the sound-producing soft tissues and nasal sacs, and that the coupling of the phonic lips and the melon acts as a waveguide for sound energy between 100 and 160 kHz to generate a forward-directed sound beam for echolocation. Peter T. Madsen Professor of Sensory Physiology Zoophysiology, Department of Biological Sciences Aarhus University, Build. 1131, CF Mollers Alle 8000 Aarhus C, Denmark Phone: 0045 89422602 email: peter.madsen@biology.au.dk Web: www.marinebioacoustics.com sender_logo