Abstract:

The hypothesis that northern elephant seals would respond to acoustic transmissions from the ATOC sound source was tested. Elephant seals were chosen because they have the best low-frequency hearing of any pinniped, are abundant, naturally migrate past the Pioneer Seamount, and are deep divers. ARGOS satellite tags provided information on animal location while at sea, while archival tags provided information on swim speed, time, depth, ambient acoustic environment, and ambient sound pressure levels. Instruments were deployed on 14 naturally migrating adult male elephant seals that were expected to swim near the source site, and upon 29 juvenile animals that were translocated and released 1 h prior to transmission. Measured mean intensity of ATOC exposure ranged from 120 to 135 dB for 60--90 Hz (n=6) compared to ambient levels of 100--107 dB (60--90 Hz). Animals did not alter return track, diving pattern, or swim speed, did not go to the surface, and often continued to dive closer to the sound source if on the descending segment of a dive. [Work funded by ONR and ARPA.]