Whales and dolphins use sound for different functions including echolocation and social communication, and thus changes in sound production patterns are a likely component of any behavioral response to anthropogenic sounds such as military mid-frequency sonar (MFA). To simultaneously log whale and dolphin movements, sound production and reception, and anthropogenic sound exposure levels, we used Dtags (Woods Hole Oceanographic Institution) and bioacoustic probes (Greeneridge Sciences). Tags were deployed on wild, free-ranging cetaceans in Southern California waters. Tagged animals were then exposed to simulated MFA or, as a control, pseudo-random noise (PRN). In total, the August-September 2010 SoCal10 behavioral response study included 28 playbacks: 19 to blue whales (11 MFA, 8 PRN), 5 to fin whales (3 MFA, 2 PRN), 2 to a single sperm whale (1 MFA, 1 PRN), 1 to a Risso’s dolphin (MFA), and 1 to a Cuvier’s beaked whale (MFA). For this analysis we focus first on baleen whale call production and reception rates (particularly blue whale D calls and variable calls) in relation to sound exposure level, dive behavior, and lunge feeding rates. We then examine echolocation-based foraging behavior and social call production by the toothed whales as a function of sound exposure level. This rich dataset, including multiple cetacean species of conservation concern, provides insight into the wide potential range of responses to sound, and the dependence of those responses on ecological, social and behavioral context. Investigations like SoCal10 can help guide inferences for related topics, such as assessment of population effects of anthropogenic noise.

The effects of anthropogenic sound on marine mammal behavior remains poorly understood, particularly with respect to fine-scale movement patterns. We exposed tagged blue whales to simulated navy sonar during the SOCAL10 behavioral response study in Southern California. We used two different high-resolution, suctioncup digital archival tags to examine fine-scale whale movement: DTAGs and Bioacoustic Probes. The Bioacoustic probe, which included a hydrophone, a pressure transducer, and a dual-axis accelerometer, allowed us to estimate speed and pitch. The DTAGs are equipped with stereo hydrophones, a pressure transducer, and three-axis accelerometers and magnetometers. These sensors allowed us to determine fine-scale movement in three dimensions and received levels of sound. Our study included 19 sound exposures, consisting of 11 playbacks of mid-frequency sonar and 8 control playbacks of pseudo-random noise. We analyzed 24 parameters related to dive and body kinematics for each dive before, during and after sound exposure. Statistical models were applied to assess the significance of changes in these parameters in relation to the received sound level and distance from the source to the whale. During some exposures there were increases in speed and changes in ascent behavior as well as an apparent displacement away from the sound source after the onset of exposure. However, no clear responses were seen in these behaviors for other exposures. Given the range of factors that can characterize behavior and the potential for infrequent or subtle reactions, these data highlight the need for sufficient baseline data and a comprehensive understanding of the behavioral (social interactions), ecological (prey distribution), and evolutionary (fight or flight) contexts in which assessments of sound effects are made. Blue whales produce low-frequency calls and have generally not been considered sensitive to mid-frequency sounds, however, the current study indicates they may respond under certain situations.

Two projects, one in the Atlantic Ocean and one in the Pacific Ocean, have simultaneously collected data from satellite-linked tags from a large number of short-finned pilot whales (Globicephala macrorhynchus; 54 from the Atlantic and 140 from the Pacific (50 from from Kaua’i), Tables 1 and 2). Pilot whales were exposed to MFAS in both areas, either opportunistically during a biannual training event at the Pacific Missile Range Facility (PMRF) in Hawai.i, or during controlled exposure experiments (CEEs) associated with the Atlantic Behavioral Response (BRS) project off Cape Hatteras, North Carolina, where experimentally simulated or operational SQS-53C sonars from surface warships were used (Figure 1). In addition, all tagged animals have some additional data known about their social relationships and context. Off Cape Hatteras this includes at minimum the number of other animals in the group they were tagged with and some photo-identification information about the associated population; off Kaua.i this includes information known about social network-derived relationships in the island-associated population and potential individual exposure histories. These data, along with newly developed spatial movement modeling techniques (Hanks et al., 2015; Johnson et al., 2021) adapted to satellite-linked tag data, create a natural experiment to evaluate and understand possible behavioral responses of shortfinned pilot whales to MFAS exposures in two different populations and environments.

On 13 and 14 May 2014, a team from the University of Washington conducted a set of measurements of the underwater sound generated by explosive charges as part of a naval training event conducted in the Silver Strand Training Complex off San Diego. Environmental measurements to support the acoustic research included measurements of sound speed versus depth showing a thermocline, and sea surface directional wave measurements. This team was joined by personnel from U.S. Pacific Fleet and HDR Inc., who conducted simultaneous observations of marine mammals.

This annual progress report covers the 2025 field season and subsequent analyses. It provides a synthesis of experimental methods; field efforts; tagging results; and exposure-response results for two CEEs, including the second operational CAS CEE conducted with the United States Ship (USS) Donald Cook and the first-ever high-power experimental source CEE simulating CAS operations. It also includes a detailed analysis of the Kinéis satellite data receiving system relative to legacy ARGOS systems. Finally, it includes a synthesis of peer-reviewed papers that have been or are in the process of being published.