Newest Humpback Whale Research Projects in Hawaiʻi

By Dr. Marc Lammers and Jean Souza

A small, instrumented package is equipped with a non-invasive suction cup to temporarily attach to a humpback whale’s back. Contributed photo

A large portion of the humpback whale population in the North Pacific Ocean return to their birth waters in Hawaiʻi each year to mate, give birth and to rear their young. Increasing numbers of these whales become noticeable as the peak months of January, February and March roll around. Thus, it is timely that this month’s article kicks off a three-part series on new and interesting findings about humpback whales in Hawaiʻi.

The Hawaiian Islands Humpback Whale National Marine Sanctuary’s research program consists of scientific staff based at its Kīhei, Maui headquarters and its worldwide network of collaborators. The research activities at HIHWNMS focus on four general categories:

• Acoustic monitoring
• Vessel/shore surveys
• Whale tagging
• Collaborations

Acoustic Monitoring

Differences in recorded humpback whale song chorusing levels off Olowalu, Maui, throughout the 2014-2020 whale seasons, as an indication of relative whale abundance. Contributed image

HIHWNMS has been involved in acoustic monitoring since 2014. Underwater sound recording devices, known as Ecological Acoustic Recorders (EARs), are placed on the seafloor in the heart of the sanctuary, in shallow and deeper coastal waters off West Maui and South Maui, each whale season between November and May. These recorders monitor the song produced by male humpback whales in this area where the density of humpback whales is among the highest in Hawaiʻi.

Monitoring humpback whale singing can tell us a lot about the comings and goings of whales in sanctuary waters. Early in the season, when there are relatively fewer whales singing, only low levels of singing are heard in the background. As more whales arrive from their northern feeding grounds, the volume of singing increases, becoming a continuous chorus. The timing and volume of the recorded song chorus can indicate when the whales first arrive, and when the whale season is peaking and when it is winding down. If monitoring occurs over multiple years, we can start to look at trends in relative whale abundance from one year to the next

Seven years of monitoring show that the sound levels, or acoustic energy, vary from one year to the next. The sound levels match up well with whale abundance trends. In the 2015/2016 whale season, there was a decline in the number of humpback whales coming to the Hawaiian Islands. This trend persisted for about three years. Then, beginning in 2018/2019, the chorusing levels started going back up again. Most recent data indicate that sound levels have gone back to the 2014/2015 levels, suggesting a recovery from the downward trend that started six years ago.

SanctSound Project

Another project that monitors underwater sound is the SanctSound Project, which occurred for the past three years at seven national marine sanctuaries and one marine national monument. This project is managed by the National Oceanic and Atmospheric Administration and the U.S. Navy.

The goal of the project has been to standardize the information collected about the soundscape within our sanctuary. This is important to better understand the sounds that are being introduced through human activity, as well as the sounds that are being produced naturally within sanctuary waters. In Hawaiʻi, the project focused on how humpback whales are utilizing our waters and habitats across the archipelago. Sound recording devices were deployed within sanctuary waters off the Main Hawaiian Islands and within Papahānaumokuākea Marine National Monument. These acoustic data were analyzed to see if trends emerged over time and over geographic areas.

Off Maui and Hawaiʻi Island, the acoustic recordings showed an increase in humpback whale chorusing levels from 2018/2019 to 2019/2020 and a later seasonal peak in 2020 compared to the prior seasons. For French Frigate Shoals, Kauaʻi, and Oʻahu, the recordings showed multiple peaks in each season. This suggests that whales were passing through these areas in pulses of abundance more pronounced than off Maui and Hawaiʻi Island, where only one or two season peaks were apparent.

Acoustical data are very valuable to the sanctuary program because the recorders can be deployed for an entire season and in areas where continuous monitoring would not otherwise be possible. The data is important to understanding humpback whale behavior, their movement patterns, and their preferred habitats while here.

Vessel Surveys

Vessel survey crew conducting transects. Contributed photo

Vessel transect surveys were started in 2018 to complement the acoustic data collection to visually validate the trends of whale abundance that were being established using the acoustic recorders.

A vessel is used off West Maui to follow systematic transect lines and count the whales along those lines. Sanctuary staff has been able to complete eight-to-ten transect lines per season for three years for a total of 26 survey days thus far. Distance sampling methods are applied to estimate whale abundance and densities (number of whales per square kilometer). This has been helpful to track and quantify whale numbers, abundance in the West Maui study area, and within and between seasons.

Data collected over three years (2019, 2020, and 2021 breeding seasons) show generally increasing numbers but some fluctuations within the increase. For example, the higher estimated density of whales in 2019/2020 was the result of a prolonged season and a later peak in that season.

Tagging Studies

Tags used by sanctuary staff are small instrumented packages that are temporarily attached to whales using suction cups. The tags are deployed on the whale using a long pole and typically stay on the whale for about four to twenty-four hours, then fall off and are retrieved. Suction cup tags are non-invasive and do not hurt the animal. They record sound, the whale’s movements and dive depth, and some also record video.

Data are used to study various aspects of whale behavior, communication, exposure to noise and habitat use. Whales conduct all their behavior in Hawaiʻi while fasting and relying on stored energy. However, little is known about how whales manage their stored energy resources during the breeding season. Many questions remain, such as on how are periods of high activity balanced with rest? Also, do daytime and nighttime activities differ?

Over the past three years (2018-2021), 32 whales have been tagged in various social roles, resulting in 174 hours of tag data. Analyses indicate that there is a shift in whale behavior around sunset, with higher level of activity in the evening than the afternoon. This is new information because researchers are not able to observe whale behavior during the evenings or at night.

Collaborations

In addition to the efforts described above, five collaborative studies with nonprofit entities, academia, and other agency partners in Hawaiʻi and elsewhere have been undertaken over the past year:

• Marine Life Conservation District Acoustic Monitoring — EARs have been deployed at Maui’s Honolua Bay, and at Manele Bay and Hulopoe Bay on Lanai to monitor the presence of spinner dolphins which use those bays for resting. In addition, changes in human activities in these areas are being monitored as COVID restrictions get lifted. Collaborators include The Nature Conservancy, University of Hawai‘i, Department of Land and Natural Resources/Division of Aquatic Resources, Oceanwide Science Institute, Hawai‘i Association for Marine Education and Research, Pulama Lanai, Ultimate Whale Watch, and Seabury Hall.
• E-Foil Noise Study — Study to find out more about e-foils, including the acoustic signatures of e-foils compared to more traditional vessels. Collaborators include DLNR-DAR, E-Foil Hawaii, and community volunteers.
• DASAR Study — Whale sounds are recorded using a vector sensor that provides the bearing or direction of the sound source. This project uses Directional Autonomous Seafloor Acoustic Recorders (DASARs) deployed on the seafloor off West Maui. Directional data for sound sources offer a new dimension for understanding the dynamics of things such as humpback whale singing. Collaborators include Scripps Institution of Oceanography, Greenridge Sciences, Inc., and local partners.
• Whale Acoustic Behavior Studies — A study to understand how juvenile males learn to sing that involves tagging of juvenile whales. Collaborators include Syracuse University and UH at Hilo.
• Social Signaling Behavior Study — A study to understand social calls and the context under which they are occurring among different social groups. Collaborators include the University of the Algarve (Portugal) and UH at Hilo.

• Marc Lammers is the Research Ecologist with HIHWNMS and heads the sanctuary’s research program. He is also an affiliate faculty member at UH’s Hawai‘i Institute of Marine Biology, and is a Co-Founder of Oceanwide Science Institute. His research focus is on understanding the population, ecology, and behavior of Hawai‘i’s humpback whales.
• Jean Souza serves as the on-site manager of Kaua‘i Ocean Discovery at Kukui Grove Center and is a Program Specialist with HIHWNMS. She can be contacted at Jean.Souza@noaa.gov