The greater increase

in descent speed (57%) vs. ascent speed (31%) following disentanglement likely highlights the effects of both drag and buoyancy related to the entangling gear and buoys. In order to dive to depth, an individual must overcome resistive buoyant forces. More active swimming is thus required on descent, while ascents can be passive (Nowacek et al. 2001). Such buoyant effects are also evident in dive shape. The overall depth- and duration-normalized dive area (DAR) was significantly lower while entangled. Dive descents to, and ascents from maximum depth were more gradual, and less time was spent in the bottom phase of the dive while the animal was entangled as compared with the behavior following disentanglement. Given that the added buoys were further from the whale than the water column was deep, Selleckchem PARP inhibitor the buoys should have never been submerged to provide an upwards buoyant force that Eg 3911 could take advantage of to conserve energy in diving (Nowacek et al. 2001). Glides occurred in all phases of the dive cycle, indicating that passive swimming was not timed to take advantage of changes in buoyancy by gliding on ascent selleck chemical while entangled. The emaciated condition of Eg 3911 may have led to negative buoyancy, as

has been found in emaciated bottlenose dolphins (Dunkin et al. 2010), and dive depths were much shallower than the predicted depth of lung collapse in cetaceans (30–235 m) (Fahlman 2008). It is thus likely that glides were employed to conserve energy (Videler and Weihs 1982, Williams 2001) rather than to optimize the benefits of buoyancy. ODBA has shown to be a reliable estimator for activity and metabolic rate in free-swimming Org 27569 animals (Fahlman et al. 2008). It was thus expected that ODBA be greater under the entangled condition; however, ODBA was often lower while entangled, compared to after disentanglement. We suggest that restraint by the drag and buoyancy of the gear may have reduced Eg 3911′s ability to make large dynamic movements. Accelerometer measurements

determine only the movement of the animal (i.e., net movement) and those forces associated, but not the forces required to move against any materials that may be restraining movement (i.e., total exertion). Consider a running parachute: the runner expends considerably more energy with the parachute, though their motion is more limited and is slower than without the apparatus. The application of ODBA to free-swimming and restrained cases likely requires separate metabolic calibrations for each condition, which are not available for entangled large whales at this time. Together, the effects of added buoyancy, added drag, and reduced swimming speed due to towing accessory gear pose many threats to entangled whales. If buoyancy overwhelms an animal’s ability to descend to the depth of its preferred prey, its foraging ability may be significantly compromised, accelerating the transition to a negative energy balance.