Sperm whale diving behavior monitored using a suction-cup-attached TDR tag

Abstract

The diving behavior of a medium-sized female sperm whale off the Kumano Coast, Japan, was studied using a suction-cup-attached TDR (time depth recorder) tag. The tag remained attached to the whale for 62 h and recorded 74 dives deeper than 100 m. The whale repeatedly dived for 30 to 45 min down to 400-1200 m. Surface intervals were generally 10 min between dives, except for a period of 1.3 to 4.2 h spent at the surface every afternoon. The whale spent long periods of time at the bottom of dives, during which there was considerable variability in both depth and velocity data, with occasional bursts in velocity. These data suggest that sperm whales use an active search-and-pursue strategy while foraging. Assuming all dives with active bottom time were for foraging, this whale spent about 80% of its total time in foraging dives. Dives with little activity at depth were occasionally observed, which were probably for resting. Although dive parameters resemble those of northern bottlenose whales, dive profiles seem to be different, suggesting that these 2 deep diving cetaceans employ different foraging strategies.