Locomotor activity by diving marine mammals is accomplished while breath-holding and often exceeds predicted aerobic capacities. Video sequences of freely diving seals and whales wearing submersible cameras reveal a behavioral strategy that improves energetic efficiency in these animals. Prolonged gliding (greater than 78% descent duration) occurred during dives exceeding 80 meters in depth. Gliding was attributed to buoyancy changes with lung compression at depth. By modifying locomotor patterns to take advantage of these physical changes, Weddell seals realized a 9.2 to 59.6% reduction in diving energetic costs. This energy-conserving strategy allows marine mammals to increase aerobic dive duration and achieve remarkable depths despite limited oxygen availability when submerged.

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The extreme body size of blue whales requires a high energy intake and therefore demands efficient foraging strategies. As an obligate lunge feeder on aggregations of small zooplankton, blue whales engulf a large volume of prey-laden water in a single, rapid gulp. The efficiency of this feeding mechanism is strongly dependent on the amount of prey that can be captured during each lunge, yet food resources tend to be patchily distributed in both space and time. Here, we measured the threedimensional kinematics and foraging behaviour of blue whales feeding on krill, using suction-cup attached multi-sensor tags. Our analyses revealed 3608 rolling lunge-feeding manoeuvres that reorient the body and position the lower jaws so that a krill patch can be engulfed with the whale's body inverted. We also recorded these rolling behaviours when whales were in a searching mode in between lunges, suggesting that this behaviour also enables the whale to visually process the prey field and maximize foraging efficiency by surveying for the densest prey aggregations. These results reveal the complex manoeuvrability that is required for large rorqual whales to exploit prey patches and highlight the need to fully understand the three-dimensional interactions between predator and prey in the natural environment.

We examined the underwater behavior of blue whales using a suction-cup-attached video-imaging instrument (Crittercam). We made 13 successful deployments (defined as tag duration 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 through fall (26 February to 30 September) between 1999 and 2003. Whale diving depth and behavior varied widely by region and period, although deployments on different individuals in the same area and period often showed very similar feeding behavior. One deployment 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 the characteristic series of vertical movements blue whales make at depth are lunges into dense aggregations of krill. These krill were visible streaming by the camera immediately before these lunges and more clearly when the whales' 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 views of the expanding throat pleats or lower jaw, and by changes in flow noise past the tag, indicating a rapid deceleration. One set of deployments 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 whale vocalization was heard on only one deployment on a male blue whale in an interacting trio of animals.