To learn about the behavioral response of elephant seals (Mirounga angustirostris) to man-made noise.
The goals of the study were to develop and test the effectiveness of a novel tag for conducting behavioral responses studies, a method used to investigate the responses of animals to particular sounds. Future use of this tag could enable researchers to answer both basic and applied ecological questions including evaluating the energetic costs of long-term exposures to anthropogenic noise and better understanding how pinnipeds respond to predator sounds in the marine environment.
As part of her M.S. research graduate student Selene Fregosi participated in the development of an active/passive acoustic tag that was deployed on the backs of several northern elephant seals (Mirounga angustirostris) as they prepared for migration from California’s Año Nuevo State Park. The goals of the study were to quantify the behavioral response of the seals to anthropogenic (man-made) noise, and evaluate the energetic cost of long-term exposure of anthropogenic noise on pinnipeds. Further, the project sought to answer basic ecological questions relating to how elephant seals respond to the sounds of predators in the marine environment.
The minimally invasive tag passively collected information on location, direction, pitch, roll, and depth of the animal concurrent with acoustic monitoring for environmental sounds. This enabled Selene to to track the animals' behavior underwater. In addition, the tags were also designed to audibly project three pre-programmed sounds: the vocalizations of non-threatening common dolphins, the vocalization of transient killer whales - a known predator of northern elephant seals - and the sound of simulated mid-frequency sonar used in naval activities. The monitoring systems on the tag enabled the behavioral responses to each of the three sounds to be recorded for analysis and further hypothesis testing.
The project, which was conducted in 2012 under the supervision of Dr. Holger Klink and in collaboration with Dr. Daniel Costa of UC Santa Cruz, will hopefully provide a new cost-effective and highly controlled method for investigating the responses of marine mammals to certain sounds, which could be used to inform regulatory agencies regarding acceptable noise levels in regions with protected marine species. The tag could also reveal currently unknown information about predator-prey interactions, an animal's use of sound to understand and respond to the environment, and potential long term implications of interactions with pervasive man-made noise, not only for elephant seals, but for many species of pinnipeds and cetaceans.
Co-PIs: David Mellinger (OSU & NOAA/PMEL), Markus Horning (OSU), Daniel Costa (UCSC), David Mann (Loggerhead instruments, Inc.), Brandon Southall (SEA, Inc.)