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Behavioral response of delphinids to sonar - supporting acoustic data

Cite this dataset

Casey, Caroline et al. (2024). Behavioral response of delphinids to sonar - supporting acoustic data [Dataset]. Dryad. https://doi.org/10.5061/dryad.d2547d88r

Abstract

Oceanic delphinids around naval operations are regularly exposed to intense military sonar broadcast within the frequency range of their hearing. However, empirically measuring the impact of sonar on the behavior of highly social, free-ranging dolphins is challenging. Additionally, baseline variability or the frequency of vocal state-switching among social oceanic dolphins during undisturbed conditions is lacking, making it difficult to attribute changes in vocal behavior to anthropogenic disturbance. Using a network of drifting acoustic buoys in controlled exposure experiments, we investigated the effects of mid-frequency (3-4 kHz) active sonar (MFAS) on whistle production in short-beaked (Delphinus delphis delphis) and long-beaked common dolphins (Delphinus delphis bairdii) in southern California. Given the complexity of acoustic behavior exhibited by these group-living animals, we conducted our response analysis over varying temporal windows (10 min – 5 s) to describe both longer-term and instantaneous changes in sound production. We found that common dolphins exhibited acute and pronounced changes in whistle rate in the 5 s following exposure to simulated Navy MFAS. This response was sustained throughout sequential MFAS exposures within experiments simulating operational conditions, suggesting that dolphins may not habituate to this disturbance. These results indicate that common dolphins exhibit brief yet clearly detectable acoustic responses to MFAS. They also highlight how variable temporal analysis windows – tuned to key aspects of baseline vocal behavior as well as experimental parameters related to MFAS exposure – enable the detection of behavioral responses. We suggest future work with oceanic delphinids explore baseline vocal rates a-priori and use information on the rate of change in vocal behavior to inform the analysis time window over which behavioral responses are measured.

README: Behavioral response of delphinids to sonar - Supporting acoustic data

https://doi.org/10.5061/dryad.d2547d88r

This data set contains information on detected whistle counts from acoustic recordings collected as part of a research project investigating the potential responses of two dolphin subspecies to simulated mid-frequency active sonar sounds. Whistles were detected using the Whistle and Moan Detector in the program Pamguard.

The associated zip file contains a single .csv for each CEE, with the filename indicating the CEE year and number (e.g., CEE2021_01_closestBuoyWhistles_1sec_20k.csv).

Column headers:

dateTime = date and time in local timezone (PST or PDT)

period = experimental period, either 'pre' for pre-exposure, 'exp' for exposure, and 'post' for post-exposure period

numWhistles = number of detected whistles that start within the 1 second specified in the dateTime column. NaNs indicate periods where no buoys were within the 1600 m distance threshold

durWhistles = sum of durations of the detected whistles that start within the 1 second specified in the dateTime column. NaNs indicate periods where no buoys were within the 1600 m distance threshold

buoy = closest buoy from which the detected whistle counts were taken

buoyDist = distance in meters between the closest buoy and the focal animals. Buoy location was tracked via buoy-mounted GPS, and focal animal location was taken from the UAS-mounted GPS. Distances are given every minute, with NaNs for each second where a distance is not available

buoyDistInterp = distance in meters between the closest buoy and the focal animals, interpolated to every 1-second resolution using linear interpolationDescription of the data and file structure

Funding

Office of Naval Research