Marine mammal (MM) monitoring was conducted during inwater pile driving (PD) at Naval Base Kitsap Bangor, Washington in Hood Canal during Fall 2011. Vessel-based monitoring was performed on construction days, during both active-construction (“AC”, defined as 30 minutes prior to, during, and 30 minutes after PD) and non-construction (“NC”, downtime) periods. Baseline surveys were also conducted throughout Hood Canal on days when no PD occurred. Monitoring and baseline surveys occurred over 53 days, during which Marine Mammal Observers (MMOs) recorded 1,207 sightings totaling 2,269 individual MM. Species observed included California sea lion (Zalophus californianus), Steller sea lion (Eumetopias jubatus), harbor seal (Phoca vitulina), and harbor porpoise (Phocoena phocoena). Harbor seals were the most frequently observed MM on construction days (n=782 sightings) and baseline survey days (n=197 sightings). The only cetaceans observed were harbor porpoise (n=68 construction, 34 baseline sightings). Harbor seal sighting rates were lower on construction days than on baseline days (0.73 and 1.80 sightings/observer hour [obs hr], respectively). Likewise, harbor porpoise were sighted less often on construction days than on baseline days (0.13 and 0.31 sightings/obs hr, respectively). On construction days, harbor seal sighting rates were actually higher during AC periods than NC periods (3.31 and 0.23 sightings/obs hr, respectively). This is consistent with MMOs’ qualitative observations that harbor seals (particularly juveniles) appeared to be attracted to PD, and often moved towards the construction area when PD was initiated. On construction days, pinnipeds were most often observed “diving,” “looking,” “sinking,” and “swimming”. During AC, 4% more pinnipeds were observed “diving” vs. NC periods (n=124). On construction days, harbor porpoise were most often observed “traveling”. During AC, 27% fewer harbor porpoise were observed “traveling” vs. NC periods (n=18). Overall, minor behavioral disruptions were observed in relation to PD, and were within “take” numbers in the issued Incidental Harassment Authorization.

In order to test the possibility of using high frequency pinger tags to track baleen whales on Navy instrumented ranges, three blue (Balaenoptera musculus) and one humpback (Megaptera novaeangliaea) whales were exposed to two high frequency pingers. The pinger frequencies were 37 and 45 kHz, with estimated received levels between 106 and 134 dB re 1 lPa. The whales were monitored prior to the exposure in order to establish their behavioral state and to acclimate them to the presence of the boat. Two of the blue whales were deep feeding, while the third blue whale and the humpback whale were traveling with intermittent bouts of possible foraging near the surface. Each exposure lasted approximately 30—40 minutes, and the whales were observed for an additional two to three surfacing intervals post-exposure. None of the blue whales demonstrated any behavioral response. The humpback whale’s response was inconclusive, as other foraging animals entered the area at the same time; however, it is likely there was no response. These data may begin to provide information on the upper frequency limits of baleen whale hearing, as these species have responded to Navy sonar-like sounds at lower frequencies but similar received levels and behavioral states.

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.

To investigate the potential impacts of naval mine neutralization exercises (MINEX) on odontocete cetaceans, a long-term passive acoustic monitoring study was conducted at a US Navy training range near Virginia Beach, USA. Bottom-moored acoustic recorders were deployed in 2012–2016 near the epicentre of MINEX training activity and were refurbished every 2–4 months. Recordings were analysed for the daily presence/absence of dolphins, and dolphin acoustic activity was quantified in detail for the hours and days before and after 31 MINEX training events. Dolphins occurred in the area year-round, but there was clear seasonal variability, with lower presence during winter months. Dolphins exhibited a behavioural response to underwater detonations. Dolphin acoustic activity near the training location was lower during the hours and days following detonations, suggesting that animals left the area and/or reduced their signalling. Concurrent acoustic monitoring farther away from the training area suggested that the radius of response was between 3 and 6 km. A generalized additive model indicated that the predictors that explained the greatest amount of deviance in the data were the day relative to the training event, the hour of the day and circumstances specific to each training event.

Opportunistic behavioral responses of baleen whales to disturbances from US Navy mid-frequency active sonar (MFAS) training at the Pacific Missile Range Facility, Kauai, Hawai’i, are being studied utilizing passive acoustic recordings. Automated passive acoustic detection, classification, localization, and tracking analyses of the data have shown a behavioral response in terms of a reduction, or cessation, of minke whale “boing” calling in response to US Navy training during the month of February 2011, 2012, and 2013 over a study area of 3,780 km2. The reduced calling is expressed as reduced minimum densities in the study area by utilizing acoustically localized individual whale counts. In February 2011, the density before sonar training was 3.64 whales while the density during sonar training was 0.69 whales (95% confidence intervals of 3.31-4.01 and 0.27- 1.8 whales, respectively). Individual ship-whale encounters have been observed to show cessation of calling from ship approaches without MFAS activity as well as ship approaches with MFAS. Sound Pressure Levels and Cumulative Sound Exposure Levels animals are exposed to are being estimated for evaluation of dose-response relationships. Tracking individual whales allows investigation of kinematics coupled with acoustic call details to establish baseline behaviors for comparison with observations during US Navy training.

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.