Introduction & Objectives

Naval Information Warfare Center (NIWC) Pacific Whale Acoustic Reconnaissance Project (WARP) Laboratory (San Diego, California) utilized passive acoustic data recordings from bottom-mounted range hydrophones at the Pacific Missile Range Facility (PMRF), Kaua‘i, Hawai‘i to monitor vocalizing cetaceans both during baseline periods and during United States (US) Navy training activities. 

Recent objectives include:

• Collect raw acoustic data for cetacean species detection, classification, localization (DCL), and tracking, and perform movement and acoustic cue rate analyses;

• Understand short-term baseline occurrence patterns and quantify minimum (snapshot) abundance estimates for multiple cetacean species;

• Continue to update our processing algorithms in order to add new species, improve existing tools, and integrate additional tools as available;

• Estimate sound levels received by cetaceans during US Navy training with mid-frequency active sonar (MFAS) from multiple sources;

• Investigate potential behavioral responses to sound exposures as well as vessel presence and movement for tracked whales, and investigate changes in dive rates across training phases for beaked whales; and

• Collaborate with researchers conducting other monitoring efforts (e.g., MFAS exposure and response by tagged animals) – including other US Navy laboratories, academic institutions, and research organizations – to fill data gaps and provide a more complete monitoring data product. 

Technical Approach

Passive acoustic monitoring (PAM) data were recorded for PMRF bottom-mounted hydrophones to support analyses of marine mammal vocalizations and MFAS transmissions. 

The Navy Acoustic Range Whale Analysis (NARWHAL) suite of algorithms was used to process recorded data.  One custom C++ algorithm automatically detects and classifies two types of baleen whale vocalizations (minke whale boing calls and low-frequency downsweep calls that could be attributable to several baleen whale species), six odontocete vocalizations (dense-beaked, goose-beaked, tropical bottlenose, and Cross Seamount beaked whale clicks, sperm whale clicks, killer whale high-frequency modulated [HFM] signals), and MFAS transmissions. A second C++ algorithm localizes detected baleen whale calls, sperm whale clicks, and MFAS transmissions. A separate Matlab Generalized Power Law (GPL) algorithm detects and localizes humpback whale song and certain types of blue whale calls. After localization, a localization association tracker (LAT) algorithm in Matlab uses spatial and temporal parameters based on general calling rate expectations for different species to connect localizations into tracks. 

A human analyst manually reviews spectrograms of the data and call intervals along the tracks produced from low-frequency downsweep calls to examine call characteristics and patterns to classify the tracks as fin whales, sei whales, Bryde’s whales, and non-specific categories of 20-Hz and 40-Hz downsweeps.

Progress & Results

The following list highlights tasks completed in FY24 in support of COMPACFLT monitoring goals:

• Raw acoustic data from 63 bottom-mounted hydrophones at PMRF were recorded at a sampling rate of 96 kHz. This report describes the collection, processing, and analysis of 7001.1 hours of new data collected and analyzed from August 2023 to September 2024 for FY24. 

• Updates and improvements to the NARWHAL analysis algorithms and workflow processes completed.

• Abundance results include: highest monthly mean number of baleen whales were: 1.6 for minke (January 2024); 0.3 for humpback (January 2024); 0.2 for sei (November 2023); 0.5 for fin (December 2023); 0.09 for Bryde’s (July 2024); 0.07 for the 20-Hz downsweep category (January 2024); and 0.08 for the 40-Hz downsweep category (January 2024).

• Abundance results of odontocetes from August 2023 to September 2024 included densebeaked whales, goose-beaked whales, Cross Seamount beaked whales, tropical bottlenose whales, killer whales, and sperm whales. 

• During the February 2024 Submarine Command Course (SCC) a total of 11 tracked whales were exposed to MFAS. One fin whale was exposed to all three primary sources of MFAS; two humpback whales were exposed to surface ship hull-mounted MFAS; two humpback whales were exposed to active sonobuoy and helicopter-dipping MFAS; and two fin, one sperm, and three humpback whales were exposed to active sonobuoys only. 

• Group foraging dive rates for all beaked whale species were analyzed before, during, and after the February and August 2024 SCCs.

Publications:

Helble, T.A., R.A. Guazzo, P.J. Dugan, G.C. Alongi, C.R. Martin, S.W. Martin, and E.E. Henderson. 2025. Twelve years of fin whale song evolution in the central North Pacific. Frontiers in Marine Science 12:1642598.

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. Exposure and response of satellite-tagged Blainville's beaked whales to mid-frequency active sonar off Kaua‘i, Hawai‘i. Movement Ecology 13(29).

Swimming and acoustic calling behavior attributed to Bryde’s whales in the central North Pacific. Frontiers in Marine Science 11:1305505.
Helble, T.A., G.C. Alongi, R.A. Guazzo, D.R. Allhusen, C.R. Martin, S.W. Martin, I.N. Durbach, and E.E. Henderson. 2024. 

Minke whales change their swimming behavior with respect to their calling behavior, nearby conspecifics, and the environment in the central North Pacific.
Helble, T.A., Guazzo, R.A., Durbach, I.N., Martin, C.R., Alongi, G.C., Martin, S.W. and Henderson, E.E. 2023. Frontiers in Marine Science 10:1148987.

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.

Behavior and inter-island movements of satellite-tagged humpback whales in Hawai’i, USA.
Henderson, E.E., J. Aschettino, M. Deakos, D. Engelhaupt, and G.C. Alongi. 2022. Marine Ecology Progress Series 685:197-213.

Dive characteristics of Cross-Seamount beaked whales from long-term passive acoustic monitoring at the Pacific Missile Range Facility, Kauaʻi.
Manzano-Roth, R., E.E. Henderson, G. Alongi, C.R. Martin, S. Martin, B. Matsuyama. 2022. Marine Mammal Science 39(1):22-41.

North Pacific minke whales call rapidly when calling conspecifics are nearby.
Martin, C.R., R.A. Guazzo, T.A. Helble, G.C. Alongi, I.N. Durbach, S.W. Martin, B.M. Matsuyama, E.E. Henderson. 2022. Frontiers in Marine Science 9:897298.

Changes in the movement and calling behavior of minke whales (Balaenoptera acutorostrata) in response to navy training.
Durbach, I.N., C.M. Harris, C. Martin, T.A. Helble, E.E. Henderson, G. Ierley, L. Thomas, and S.W. Martin. 2021. Frontiers in Marine Science 8:660122.

Singing fin whale swimming behavior in the Central North Pacific.
Guazzo, R.A., I.N. Durbach, T.A. Helble, G.C. Alongi, C.R. Martin, S.W. Martin, and E.E. Henderson. 2021. Frontiers in Marine Science 8:696002.

Dive and movement behavior of a humpback whale competitive group and a multiday association between a primary escort and female in Hawaiʻi.
Henderson, E.E., M. Deakos, and D. Engelhaupt. 2021. Marine Mammal Science. https://doi/,org/10.1111/mms.12891

Helble, T.A., Guazzo, R.A., Martin, C.R., Durbach, I.N., Alongi, G.C., Martin, S.W., Boyle, J.K. and Henderson, E.E., 2020. Lombard effect: Minke whale boing call source levels vary with natural variations in ocean noise. The Journal of the Acoustical Society of America, 147(2), 698-712.  https://doi.org/10.1121/10.0000596

Quantifying the Behavior of Humpback Whales (Megaptera novaeangliae) and Potential Responses to Sonar. Henderson, E., J. Aschettino, M. Deakos, G. Alongi, and T. Leota. 2019. Aquatic Mammals, Vol 45, Iss 6.

Identifying behavioral states and habitat use of acoustically tracked humpback whales in Hawaii.
Henderson, E.E., T. A. Helble, G.R. Ierley, and S.W. Martin. 2018. Marine Mammal Science 34:701-717.

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.

Swim track kinematics and calling behavior attributed to Bryde’s whales on the Navy’s Pacific Missile Range Facility
Helble, T.A.,  E. E. Henderson, G.R. Ierley, and S.W. Martin. 2016. Journal of the Acoustical Society of America 140:4170-4177.

Occurrence and habitat use of foraging Blainville’s beaked whales (Mesoplodon densirostris) on a U.S. Navy range in Hawaii.
Henderson, E.E., S.W. Martin, R. Manzano-Roth, and B. M. Matsuyama. 2016. Aquatic Mammals 42(4):549-562.

Impacts of U.S. Navy training events on Blainville’s beaked whale (Mesoplodon densirostris) foraging dives in Hawaiian waters.
Manzano-Roth, R., E.E. Henderson, S.W. Martin, C. Martin, and B.M. Matsuyama. 2016. Aquatic Mammals 42(4):507-518.

Minke whales (Balaenoptera acutorostrata) respond to navy training
Martin, S.W., C.R. Martin, B.M. Matsuyama, and E.E. Henderson. 2015. Journal of the Acoustical Society of America 135:2533-2541.