Single source sound production and dynamic beam formation in echolocating harbour porpoises (Phocoena phocoena)

Abstract

SUMMARYEcholocating 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.

Somatosensation, Echolocation, and Underwater Sniffing: Adaptations Allow Mammals Without Traditional Olfactory Capabilities to Forage for Food Underwater

“…The signals then pass through the melon on the forehead, a structure consisting of special fats that serve to focus outgoing sound waves and project the waves forward (see Fig. 2); interestingly, the melon may filter out frequencies higher than 160 kHz (Madsen et al, 2010;Jones, 2005). Recent research demonstrates that in short-distance prey tracking, the harbor porpoise only produces clicks with the right pair of phonic lips, despite possessing a pair on the left side as well (Madsen et al, 2010).…”

“…2); interestingly, the melon may filter out frequencies higher than 160 kHz (Madsen et al, 2010;Jones, 2005). Recent research demonstrates that in short-distance prey tracking, the harbor porpoise only produces clicks with the right pair of phonic lips, despite possessing a pair on the left side as well (Madsen et al, 2010). Using just the right pair, dolphins are still able to vary sound output and direction of echolocative clicks (Madsen et al, 2010).…”

Comparative anatomical study of sound production and reception systems in the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena) heads

“…The harbour porpoise which uses only clicks should develop more the right respiratory system (organs responsible of the clicks production). However, the use of the left respiratory system can't be excluded because pressure variations in the left nasal passage are noted during the emission of soundwaves (great amplitude) (Madsen et al, 2010).…”

“…According to many authors (e.g. Amundin, 1991;Madsen, Wisniewska, & Beedholm, 2010), the whistles are often used in order to communicate and the clicks like a sonar.…”

Acoustic monitoring and prey association for beluga whale, Delphinapterus leucas, and harbor porpoise, Phocoena phocoena, off two river mouths in Yakutat Bay, Alaska

“…Beluga produce typical delphinid broad-band echolocation clicks with center frequencies between 50 kHz and 110 kHz, while harbor porpoise produce typical phocoenid nar-row-band high frequency clicks with a center frequency of 110 to 150 kHz. (Au, 1993 ;Au et al, 1999;Lammers and Castellote, 2009;Madsen et al, 2010;Castellote et al, 2013). The goals of this study were to determine the seasonal distribution of beluga and harbor porpoise in Yakutat and whether their presence in river mouths was related to its potential prey fi eld.…”