Title

A Novel Sound Recorded in Association with Bottom Feeding in Humpback Whales

Abstract

Acoustic studies of baleen whales are becoming increasingly common. However, a minority of studies combine acoustic data with technologies that allow sound production to be placed in a behavioral context. Noninvasive digital acoustic recording tags (DTAGS) were attached to humpback whales (Megaptera novaeangliae) on the western North Atlantic’s Great South Channel feeding grounds during July 2004 to study foraging and acoustic behavior. Acoustic records totaling 48.4 data hours from four attachments were aurally and automatically analyzed, and a novel sound was identified. The sounds are repetitive, complex bursts, consisting of two components (approximately 50 ms each, peak frequencies between 50 and 400 Hz), and produced at an average rate of 1.6 (±SD 0.25 s) pulsed pairs per second. The bursts were heard in bouts ranging from 0.5 to 79 seconds (mean 17 s). These sounds were recorded from all four tagged whales, totaling 344 clear bouts of pulses. Acoustic properties were consistent among the four individuals, though there was some variation in bout duration. Acoustic analysis was combined with virtual behavioral study using GeoZui4D and other track visualization software to investigate whether the sounds were associated with foraging behavior. The bursts only occurred during portions of the dive cycle greater than 60m in depth (mean depth 77 m, ±SD 3.7 m), usually within a few meters of the sea floor. Bouts often began upon reaching the foot of a dive, or were associated with animals sharply rolling on their side. Passive recordings of these sounds could indicate geographical locations of subsurface feeding by humpback whales. However, the frequency range and received levels (subsampling indicated a maximum sound pressure level of approximately 145 dB peak re 1µPa — substantially lower than humpback whale song) overlap with sounds from commercial shipping, suggesting that the signals could be masked by ocean noise.

Publication Date

12-2005

Journal or Conference Title

Biennial Conference on the Biology of Marine Mammals (CBMM)

Volume

16th

Pages

269

Conference Date

Dec 12 - Dec 16, 2005

Publisher Place

San Diego, CA, USA

Publisher

The Society for Marine Biology

Document Type

Conference Proceeding

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