Localization and visual verification of a complex minke whale vocalization

A recently described population of minke whales (Balaenoptera acutorostrata ) offered a unique opportunity to study its acoustic behavior. The often-in quisitive dwarf minke whale is seen on the Great Barrier Reef nearly coinci dent with its suspected calving and breeding seasons. During drifting encou nters with whales, a towed hydrophone array was used to record sounds for s ubsequent localization of sound sources. Shipboard and in-water observers l inked these sounds to the closely circling minke whale. A complex and stere otyped sound sequence, the "star-wars" (SW) vocalization, was recorded duri ng a series of visual and acoustic observations. The SW vocalization spanne d a wide frequency range (50 Hz-9.4 kHz) and was composed of distinct and s tereotypically repeated units with both amplitude and frequency-modulated c omponents. Broadband source levels between 150 and 165 dB re 1 mu Pa at I m were calculated. Passive acoustic studies can utilize this distinct vocali zation to help determine the behavior, distribution, and movements of this animal. While the SW vocalization's function remains unknown, the regularly repeated and complex sound sequence was common in low latitude, winter mon th aggregations of minke whales. At this early stage, the SW vocalization a ppears similar to the songs of other whale species and has characteristics consistent with those of reproductive advertisement displays. (C) 2001 Acou stical Society of America.