Insights into the underwater diving, feeding, and calling behavior of blue whales from a suction-cup-attached video-imagen tag (Crittercam)

Abstract

We examined the underwater behavior of blue whales using a suction-cup-attached video-imaging instrument (CRITTERCAM). We made 13 successful deployements (defined as tag during of >15 min and successful recovery of the tag and data) totaling 19 hours of CRITTERCAMS on blue whales off California and in the Sea of Cortez from spring througth fall (26 February to 30 September) between 1999 and 2003. Whale diving depth and behavior varied widley by region and period, although deployements on different individuals in the same area and period ofter shoed very similar feeding behavior. One deployement extending into night showed a diurnal shift in diving behavior with progressively shallower feeding dives as it became dark, with shift to shallow, apparently non-feeding dives during the night. Data and video from tags demonstrated that characteristics series of vertical movements blue whales make at depth are lunges into dense agggregations of kill. These krill were visible streaming by the camera inmediately befor these lunge and more clearly when the wales' forward motion stopped as a result of the lunge. The progression of events leading up to and during the lunge could be documented from the head movement of whales and occasional viwws of the expanding throat pleats or lowe jay, and by changes in tlow noise past the tag, indicationg a rapid deceleration. One set of deployements in the Southern California Bight revealed consistent feeding at depths of 250-300 m, deeper than has been previously reported for blue whales. A loud blue whales vocalization was heard on only one deployement on a male blue whale in an interactiong trio of animals