| 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 and acoustic (time/depth) tags have been used. For studying captive animals, arrays and video techniques as well as miniature acoustic-behavioral tags have been used. While searching for prey, captive harbor porpoises used clicks with intervals longer than 50 ms. After detecting the prey, the click interval stabilized at about 50 ms and then became progressively shorter while approaching the prey. During this time the source levels of clicks decrease by about half (6dB) for each halving of distance to 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. (We acknowledge Magnus Wahlberg, Fjord&Bælt, Kerteminde, Denmark.)
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