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.
[2017-10-27] The data sheets in the zipped shapefile download file are updated.
[2017-09-26] The number of localizations has increased by about 400 based on a more correct method of counting calls.
Four moored hydrophone arrays were used to detect. Hydrophone, Latitude, Longitude, Depth, Channel NE 36.43778, -121.94417 52, 1 NW 36.43512, -121.96082 95, 2 SE 36.42679, -121.93743 43, 3 SW 36.41872, -121.94925 79, 4
The original data sheets provided by the provider are included in the downloadable zip file. To get it, choose "Dataset on Dataset Page" and "As shapefile" as desired options through the download processes on the OBIS-SEAMAP Dataset Page.
The sheet labeled M3 contains attributes of each of the M3 calls that were localized. JulianTime: Matlab's datenum. Days since January 0, 0000 Latitude: Localized latitude of call Longitude: Localized longitude of call Tracked: 0 if not part of a track, 1 if call was part of track WaterDepth: Depth in meters RangeXX: Range to each of the hydrophones (NE,NW,SE,SW) Duration_XX: Duration of call in seconds at each hydrophone RL_rms_XX: Root Mean Square received level at each hydrophone (µPa) RL_p2p_XX: Peak-to-Peak received level at each hydrophone (µPa) SL_rms_XX: Root Mean Square source level at each hydrophone (dB re 1 µPa) SL_sel_XX: Sound Exposure Level source level at each hydrophone (dB re 1 µPa^2*s) SL_p2p_XX: Peak-to-Peak source level at each hydrophone (dB re 1 µPa) PeakFreq_XX: Peak frequency at each hydrophone (Hz) BW_3dB_XX: 3 dB Bandwidth around peak frequency at each hydrophone (Hz) MeanFreq_XX: Mean frequency at each hydrophone (Hz) SigmaBW_XX: +/- sigma bandwidth at each hydrophone (Hz)
The sheet labeled M1 contains attributes of each of the M1 calls manually detected on a single hydrophone (NE) JulianTime: Matlab's datenum. Days since January 0, 0000 IPI: mean inter-pulse interval between pulses within a call IPI_SD2: variance of inter-pulse intervals between pulses within a call NumPulses: Total number of pulses within a call PeakFreq_NE: Peak frequency at NE hydrophone (Hz) BW3dB_NE: 3 dB Bandwidth around peak frequency at NE hydrophone (Hz) MeanFreq_NE: Mean frequency at NE hydrophone (Hz) SigmaBW_NE: +/- sigma bandwidth at NE hydrophone (Hz)
The sheet labeled M3 contains noise levels for every minute of recording JulianTime: Matlab's datenum. Days since January 0, 0000 NoiseLevel_XX: Root median square noise level for the one minute period starting at JulianTime (µPa) on the recordings from each hydrophone
This section explains attributes included in the original dataset.
OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only.
Should you need other attributes described here, you are encouraged to contact the data provider.
Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.
Attributes in dataset
Attribute (table column)
Unique ID number (generated by OBIS-SEAMAP)
Julian time, Matlab
Date and time of the detection
Latitude in decimal degrees
Longitude in decimal degrees
Species name recorded
Taxonomic Serial Number added by OBIS-SEAMAP
Group size (blank; presence only)
1 if call was verified as a gray whale M3 on NE hydrophone, 0 otherwise
1 if call was part of a track of verified gray whale calls, 0 otherwise
1 if a call was localized within the array and could be verified as a gray whale M3 call when looking at spectrograms from all four hydrophones, 0 otherwise
Time difference of arrival (TDOA) in seconds between NW and NE hydrophones
Time difference of arrival (TDOA) in seconds between SE and NE hydrophones
Time difference of arrival (TDOA) in seconds between SW and NE hydrophones
Detection start time in samples since the start of the deployment
Detection end time in samples since the start of the deployment
Mean of samplestart and sampleend
Least-squared difference between the theoretical and measured TDOAs summed over the three TDOA measurements