Recording Underwater Sounds of Free-Ranging Dolphins While Underway in a SmallBoat

摘要

Few studies of vocalizations of free-ranging cetaceans have successfully linkedcontinuous, underwater recordings with ongoing behavioral observations. Noise from engines and/or water flowing around hydrophones generally limited researchers to recording sounds from stationary sites or from boats with their engines turned off, especially if the sounds of interest were in the same frequency range as that of engine or flow noise. But unless the animals stay in one place, these techniques do not allow for longterm recording sessions, or for simultaneous detailed behavioral observations. Sailboats are more difficult to maintain at a steady distance from the animals, and they still produce substantial flow noise around a towed hydrophone. Existing towed hydrophone systems are unwieldy and not practical for use by one or two persons in a small power boat, especially in areas heavily trafficked by boats. Therefore, we designed an inexpensive, portable system tailored to record whistles (ranging from about 5 to 25 kHz) of bottlenose dolphins (Tursiops truncatus), while they are being followed in a small boat.