We are proud to report the publication of our paper “Behavioral responses of goose-beaked whales (Ziphius cavirostris) to simulated military sonar” in the journal Ecosphere. You can access the full text of the open access paper, led by Brandon Southall, here. The paper reports the results of a set of complex field experiments conducted between 2017 and 2022 to examine the behavioral response of goose-beaked whales to mid-frequency (3–4 kHz) active sonar (MFAS) signals. These signals simulate powerful Navy sources that have been associated with multiple stranding events of this species.
The paper is remarkable in several respects. First, our sample size of tagged whales (53) exposed to the simulated MFAS signals is an order of magnitude greater than of all previous experiments with this species combined. Second, we expanded the duration of monitoring these whales from days to months by deploying 50 satellite-transmitting dive recorders, in addition to 3 short-duration digital acoustic tags. Third, we conducted a large number (13) of experimental trials, resulting in 72 exposure events to individual whales.
Whales were exposed at received sound levels from below ambient noise levels to 142 dB re: 1μPa (RMS). We observed similar patterns of minor behavioral changes for control trials (no sound exposure) and low received levels (<100 dB). Above 100 dB RLs, we observed a consistent set of responses that included extended deep dives, prolonged periods between deep dives, directed movement away from the source, and cessation of echolocation.
The results of our experimental trials add to the growing body of evidence supporting the risk-disturbance hypothesis, which posits that goose-beaked whales perceive and respond to MFAS signals in the same manner they respond to the sounds of predators, such as killer whales (Orcinus orca). Goose-beaked whales rely on crypsis as an anti-predator behavior and respond to MFAS signals in the same manner, by going quiet and moving away from the source of the sound. Importantly, these responses are transitory in nature and exposed whales quickly returned to normal patterns of ranging and diving patterns.
This paper is the first of two to examine the response of goose-beaked whales to MFAS signals. Thes second, which describes the response of tagged whales to real sonar signals produced by Navy warships, will be out later this year. We are grateful to the U.S. Navy’s Marine Species Monitoring Program for supporting this important research.
