Abstract:

The description of minke whale (balaenoptera acutorostrata) vocalizations is sparse with little recent study. In addition, the minke and some of its assumed vocalizations are not definitively linked. To address this problem, recordings were made at a unique site off the Great Barrier Reef where minkes maintain long, close contacts (to 10 h) with vessels. During these encounters a 200-m, four-element hydrophone array (Hi-Tech HTI-SSQ41B, 10 Hz--30 kHz) was deployed and digitally recorded onto a Tascam DA-38 (0--22 kHz). Time of arrival differences between hydrophones were used to obtain hyperbolic fixes on nearby sound sources. With this method, a new vocalization consisting of three short pulses (pulse duration 100 ms, peak energy 200--250 Hz, with significant energy between 1.5 and 2 kHz) followed by a slight upsweep (trail of 1 s) has been definitively linked to the minke. Source levels of at least 155 dB re: 1 (mu)Pa were estimated. Similar vocalizations with varying pulse numbers (to at least 7), and low frequency grunts and moans (80--4000 Hz) were recorded. Approximately 19 h were recorded in the close presence of 45 minke whales along with 18 h of ambient recordings. These recordings greatly contribute to the sparse database of known minke vocalizations. [Work supported by ONR and the R/V Undersea Explorer.]