Development and Evaluation of an Animal-borne Active Acoustic Tag to Conduct Minimally Invasive Behavioral Response Studies on Marine Mammals

• Main Author: Fregosi, Selene
• Other Authors: Klinck, Holger, Horning, Markus, Southall, Brandon L., Fisheries and Wildlife, Oregon State University. Graduate School
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Elephant seals > Behavior; Underwater acoustics > Instruments; Elephant seals > Marking; Elephant seals > Effect of noise on; Elephant Seals; Killer Whale; Sperm whale; Killer whale
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/dn39x4410

Development of new research tools is needed to better understand the potential effects of a noisier ocean on individual and populations of marine mammals. Current behavioral response studies utilize ship-mounted sound sources to induce short-term noise-related behavioral responses in tagged animals. Combining the tag with the sound source into an animal-mounted active acoustic and motion sensing tag could potentially allow for long-term, more controlled and cost-effective behavioral response studies. Field tests were conducted on juvenile northern elephant seals, Mirounga angustirostris, using both natural and anthropogenic stimuli, to evaluate the potential of such a prototype tag. Results showed that such an instrument does elicit behavioral responses in tagged individuals. Responses during the ascending phase of a dive consisted of a dive inversion, with the animal diving as deep as or deeper than its original dive depth (seven of nine exposures). Change in dive depth following exposure was significantly larger than change in depth for non-exposure inversions. A single exposure at the bottom phase of a deep dive followed the same pattern. Dive inversions were observed following white noise, sperm whale clicks, killer whale whistles, and sonar exposures, but not following common dolphin whistles. Responses to exposures received during the descending phase of a dive resulted in an increased descent rate in nine of ten exposures. All eight exposures during shallow dives, where the animals were likely limited by bathymetry from diving any deeper, were characterize by increased flow noise following exposure, an indicator of increased swim speed. Results showing differential responses to specific exposure stimuli were inconclusive. Tag improvements and additional field efforts are needed to validate the tag’s use in behavioral response studies to specific acoustic stimuli. There is potential to use this technology to study physiological effects of extended deep dives on marine mammals as well as frequency dependent ...