Gray whale (Eschrichtius robustus)

Tags have been used to examine migration routes and habitat use of large whales for >40 yr, however, evaluation of tag wound healing has largely been short-term, anecdotal or generalized. This study developed methods for systematic photographic assessment of long-term external consequences of tag placement, to determine potential differences in wound healing between species and tag types and thus advise future tagging efforts to possibly minimize undesirable side effects.

As awareness of the effects of anthropogenic noise on marine mammals has grown, research has broadened from evaluating physiological responses including injury and mortality to considering effects on behavior and acoustic communication. Most mitigation efforts attempt to minimize injury by enabling animals to move away as noise levels are increased gradually. Recent experiences demonstrate that this approach is inadequate or even counterproductive for small, localized marine mammal populations, for which displacement of animals may itself cause harm.

During the northbound migration, a small number of individually identified gray whales (n=14) divert from the migratory path to enter the Strait of Juan de Fuca, travelling >100 miles to northern Puget Sound (NPS), where they feed on dense patches of ghost shrimp. Efforts to photographically identify these whales began in 1990, and most of these whales (71%) have been sighted in NPS in at least ten of the past 24 years. These whales arrive in NPS in the spring and feed for 2-3 months.

The majority of eastern North Pacific gray whales feed in the Bering, Chukchi, and Beaufort Seas. Photo-ID and genetics have shown that a subset of this population, the Pacific Coast Feeding Group (PCFG), is a somewhat distinct group of about 200 individuals known to feed through the summer and fall from N California to SE Alaska. Recruitment to this group is an important consideration in understanding its status and management. A large scale collaborative effort was initiated in 1998 to monitor PCFG whales.

Bio-logging approaches to study the biology of free-ranging animals often focus on audio, movement, or video, but rarely are these different data streams integrated. Here we custom engineered a tag to measure the fine-scale kinematics of cetaceans while simultaneously recording animal-borne video from dual cameras. The movement sensors included a pressure transducer, tri-axial inertial sensors (accelerometers, magnetometers, gyroscopes), and a paddle-wheel speed sensor.