Gray whale localized acoustic detections in Granite Canyon 2014-2015

Original provider:
Regina A. Guazzo, Scripps Institution of Oceanography

Dataset credits:
Scripps Institution of Oceanography, University of California San Diego

Abstract:
Eastern North Pacific gray whales make one of the longest annual
migrations of any mammal, traveling from their summer feeding areas in
the Bering and Chukchi Seas to their wintering areas in the lagoons of Baja
California, Mexico. Although a significant body of knowledge on gray whale
biology and behavior exists, little is known about their vocal behavior while
migrating. In this study, we used a sparse hydrophone array deployed
offshore of central California to investigate how gray whales behave and
use sound while migrating. We detected, localized, and tracked whales for
one full migration season, a first for gray whales. We verified and localized
10,644 gray whale M3 calls and grouped them into 280 tracks. Results
confirm that gray whales are acoustically active while migrating and their
swimming and acoustic behavior changes
on daily and seasonal time scales. The seasonal timing of the calls verifies
the gray whale migration timing determined using other methods such as
counts conducted by visual observers. The total number of calls and the
percentage of calls that were part of a track changed significantly over both
seasonal and daily time scales. An average calling rate of 5.7
calls/whale/day was observed, which is significantly greater than
previously reported migration calling rates. We measured a mean speed of
1.6 m/s and quantified heading, direction, and water depth where tracks
were located. Mean speed and water depth remained constant between
night and day, but these quantities had greater variation at night. Gray
whales produce M3 calls with a root mean square source level of 156.9 dB
re 1 µPa at 1 m. Quantities describing call characteristics were variable and
dependent on site-specific propagation characteristics.