| Summary: | The harbor porpoise (Phocoena phocoena) is a small toothed whale living mostly in coastal waters. There are large, but unknown, numbers in the inner Danish waters. Four are in captivity at Fjord & Bælt, Kerteminde, Denmark, one of which was born here in 2006. Harbor porpoises use their ultrasonic clicks as biosonar for orientation and detection of prey (mostly smaller pelagic and bottom dwelling fish), and for communication. For studying wild animals, hydrophone arrays [Villadsgaard et al. J.Exp.Biol. 210 (2007)] and acoustic (time/depth) tags [Akamatsu et al. Deep Sea Research II 54 (2007)] have been used. For studying captive animals, arrays and video techniques [Verfuss et al. J.Exp.Biol. 208 (2005)] as well as miniature acoustic-behavioral tags [Deruiter et al. JASA 123 (2008)] have been used. While searching for prey, harbor porpoises use clicks at long intervals (~50 ms) that progressively decrease when closing on an object. After detecting the prey, the click interval stabilizes and then becomes progressively shorter while approaching the prey. The sequence ends in a terminal, high repetition rate buzz (~500 clicks/s) just before capturing the prey (a video will be shown). The temporal sequence differs from that of beaked whales, but is like that of bats.
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