PROJECTS

2023-2024 Overview -

Cascadia Research Collective (CRC) undertook field work off the Pacific Missile Range Facility (PMRF) in 2023 and 2024, continuing long-term odontocete photo-identification and satellite tagging efforts conducted in the Hawaiian Islands for more than 20 years. Tagging was conducted August 6-13, 2023, and February 11-19, 2024, and a summary of the 22 individuals that were tagged, including their tag duration and overlap with SCC phases, is provided in Henderson et al. (2025). In 2023, six short-finned pilot whales, two common bottlenose dolphins, one pantropical spotted dolphin, and one melon-headed whale were tagged. In 2024, eight pilot whales, one bottlenose dolphin, and three humpback whales were tagged. All but one of the 23 animals tagged at PMRF in 2023 and 2024 that successfully transmitted location data had a direct transmission path during at least part of Phase B of the SCCs. A summary of tagged individuals, including exposure durations and maximum median received levels, are presented in Henderson et al. (2025).

2021-2022 Overview - 

Satellite-tagging efforts were conducted before Submarine Command Course (SCC) training events in August 2021 and 2022 at PMRF off the island of Kauaʻi. Researchers tagged 21 delphinids to observe their behavior before, during, and after the SCCs, to estimate received levels (RLs) of mid-frequency active sonar (MFAS).  Fifteen of the tagged individuals remained in the area or had direct acoustic paths between their locations and surface ship hull-mounted MFAS sources, allowing received level estimation through propagation modeling.

This group included: 

• 6 short-finned pilot whales (Globicephala macrorhynchus)

• 1 false killer whale (Pseudorca crassidens) 

• 5 melon-headed whales (Peponocephala electra) 

• 1 rough-toothed dolphin (Steno bredanensis) 

• 2 common bottlenose dolphins (Tursiops truncatus)  

For all animals, the maximum median received sound pressure levels ranged from 73 to 148 dB re 1 μPa. Eight animals moved out of the area before the onset of MFAS, resulting in maximum median RLs at or below 100 decibels (dB) re 1 μPa. The remaining seven were near the range during MFAS and had higher estimated RLs, although none exceeded 156 dB re 1 μPa (including +2*SD). Observed behavior differences include: changes in dive depth and duration between SCC phases, dive rates, and time spent at or near the surface. However, no consistent behavior changes were observed either within or across species. No changes in horizontal movement were observed relative to periods of MFAS. 

2014-2020 Overview - 

All tag data obtained in 2014 through 2020 were utilized in analyses of received level and movement and dive behavior. In this study, while there were statistical differences in dive behavior of all three species across the periods of the SCC, there were no apparent consistent patterns indicating broad, sustained responses to MFAS (e.g., large-scale habitat abandonment). There were often inter-individual differences in how dive behavior changed across periods, with some instances of behavioral changes more apparently related to the lunar cycle than to training activity.

There are a few instances where a behavioral response appeared to have occurred at a relatively coarse scale based on the timing of events and apparent movement, as individuals moved towards the region of activity on PMRF and then changed the direction of their travel away during a period of MFAS. However, there were also sharp changes in direction of travel during baseline and non-MFAS periods. A more detailed quantitative analysis may be able to tease apart these differences to determine what may constitute a behavioral response.

Although no overt, broadly evident behavioral responses seem to have occurred, there were several instances of animals occurring and apparently continuing to remain quite close to active ships. We estimate that these individuals received some of the higher levels of MFAS exposure yet documented for any marine mammal species. Although vastly improved over previous RL estimates there is still positional uncertainty in these data; while the highest median levels in these close exposure cases were approximately 175 dB re 1µPa, the median levels plus two standard deviations were around 195 dB re 1µPa, and maximum modeled levels exceeded 200 dB re 1µPa. While the probability of reaching those maximum levels was quite low, these results do indicate that in some cases odontocetes at PMRF may be experiencing very high RLs that could approach temporary or potentially even permanent threshold shift levels, provided animals experienced these conditions for some more extended exposure. 

Publications:

Exposure and response of satellite-tagged Blainville's beaked whales to mid-frequency active sonar off Kaua‘i, Hawai‘i
Henderson, E.E., M.A. Kratofil, R.W. Baird, C.R. Martin, A.E. Harnish, G. Alongi, S.W. Martin, and B.L. Southall. 2025. Movement Ecology 13(29).

Rough-toothed dolphin exposures to U.S. Navy mid-frequency active sonar at the Pacific Missile Range Facility, Hawai‘i

Martin C.R., Henderson, E.E., Baird, R.W., Kratofil, M.A. and Martin, S.W. 2024. Detection, Classification, Localization, and Density Estimation of Marine Mammals Workshop. June 3–7, 2024. Rotterdam, The Netherlands.

Behavioral Response of Blainville’s Beaked Whales (Mesoplodon densirostris) to U.S. Navy Training Activity 

Henderson, E.E., R.W. Baird, C.R. Martin, M.A. Kratofil, A.E. Harnish, S.W. Martin, and B.L. Southall. 2024. 8th International Bio-Logging Science Symposium. 4–8 March 2024. Tokyo, Japan.

Beaked Whale Behavioral Responses to Navy Mid-Frequency Active Sonar.

Henderson, E.E. 2023. In: Popper, A.N., Sisneros, J., Hawkins, A.D., Thomsen, F. (eds) The Effects of Noise on Aquatic Life. Springer, Cham.

Improved Satellite Tag Track Analyses and Received Level Estimation of Odontocetes During Navy Training at PMRF.

Henderson, E.E., C.R. Martin, M.A. Kratofil, S.W. Martin, R.W. Baird, B.L. Southall. 2022. Effects of Sound on Marine Mammals Conference, Beaufort, North Carolina, 15-18 March 2022.

Quantifying the response of Blainville's beaked whales to US Naval sonar exercises in Hawaii.

Jacobson, E.K., E.E. Henderson, D.L. Miller, C.S. Oedekoven, D.J. Moretti, L. Thomas. 2022. Marine Mammal Science 38(4):1549-1565.

Estimating received levels for acoustically tracked whales from Navy mid-frequency active sonar.
Martin, C.R., S.W. Martin, and E.E. Henderson. 2018. Journal of the Acoustical Society of America 144: 1885-1886.