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Abstract: Sperm whale (Physeter macrocephalus) is one of the common cetacean species inhabiting the western Mediterranean Sea. The aim of this study was to describe the dive cycle of sperm whales in this region and gain insight into their foraging activity. Dedicated summer field seasons were conducted from 2001-2003. Visual and acoustic measures were undertaken and their relationships analyzed. The measures included surface/dive periods, blow rate, distance traveled, timing of clicks & creak activity, and inter-pulse interval measurements of sperm whale clicks. The whales exhibited dive cycle parameters consistent with those measured in other parts of the world: approximately 45 min dive duration, 9 min surface period (i.e., inter-dive interval), with 5 blows/min, and 1.3 nmi horizontal displacement between dives. An average of 25 creaks per dive were registered. Whale body size appeared to be significantly related with both the number of creaks per dive and the dive time at which the first creak occurred, suggesting that larger whales may increase their prey intake and use deeper water layers than smaller whales. The timing of the first creak and the last click of the dive (around 6 min after fluke-up, and just before the surfacing, respectively) suggest a foraging depth of between 500 and 800 m, based on known descent and ascent rates.
Key Words: Sperm whale, dive, feed, click, Mediterranean Sea, Physeter macrocephalus
Document Type: Research article
Page Numbers: 419-426