Maui Humpback Whale Tagging: reflecting on a record-breaking 2025 season and preparing for new horizons in 2026
- Gussie Hollers
- 2 days ago
- 4 min read
Updated: 2 days ago
Written by Gussie Hollers
In February 2026, members of the MMRP will head over to Maui for our seventh consecutive humpback whale tagging season! We will be deploying non-invasive Customized Animal Tracking Solutions (CATS) suction-cup tags on humpback whales for our research on their behavior and energy usage, and collaborating with partners to advance tag deployment technology and physiological measurement techniques. In preparation for our 2026 season, we wanted to reflect on our outstanding 2025 season accomplishments: tagging a record 32 whales, including 11 mothers, 14 male escorts, three males in competitive groups, one singer, and three calves.
Collecting CATS tag data is essential for our lab’s work forecasting North Pacific humpback whale population trends using the Population Consequence of Disturbance modeling framework. After decades of recovery following the end of commercial whaling, humpback whales are now facing a new set of challenges. Human activities such as vessel traffic and noise, combined with changing ocean conditions, are altering when and where whales find food, and how much energy they must spend to survive and reproduce. Because humpback whales are long-lived and travel across vast distances, changes in population rates can take many years to detect. To help managers make timely conservation decisions, scientists use population models that forecast how today’s conditions may affect whale populations in the future. These models depend on understanding how stressors influence individual whales, especially how disturbances change their behavior, energy use, and ultimately their ability to reproduce and raise calves.
Paired with Unoccupied Aerial Systems (UAS/drone) photogrammetry, CATS tags can be used almost like fitbits for whales, allowing us to estimate how many calories individual whales use during different behaviors. For example, we can use the tags to calculate how much energy whales save by resting, and how much energy it would cost them to swim away from an incoming boat. We can also compare the calorie cost of different mating strategies. In 2025, we began tagging more male whales to compare those breeding strategy energy costs for Lewis’s Evans’s PhD research. Different mating behaviors require different amounts of energy, with some much more costly than others.
Paired with Unoccupied Aerial Systems (UAS/drone) photogrammetry, CATS tags can be used almost like fitbits for whales, allowing us to estimate how many calories individual whales use during different behaviors. For example, we can use the tags to calculate how much energy whales save by resting, and how much energy it would cost them to swim away from an incoming boat. We can also compare the calorie cost of different mating strategies. In 2025, we began tagging more male whales to compare those breeding strategy energy costs for Lewis’s Evans’s PhD research. Different mating behaviors require different amounts of energy, with some much more costly than others.
Singing is one mating behavior requiring little movement energy. Singing males remain stationary underwater at about 20-30 meters depth, singing for hours in bouts of about 15 minutes each.
Escorting behavior requires more movement than singing, but is still a less energetically costly mating strategy. Escort males often follow single females or mother-calf pairs. These males rest and travel with the females, and occasionally defend the female from a new incoming male.
The mating strategy requiring the most energy is competitive groups. These groups consist of multiple males (sometimes up to 20-30 individuals) following a single female while jockeying for position and often swimming at high speeds, head lunging, tail slapping, breaching, and headbutting each other. These competitive groups can last for days, costing the males large amounts of energy.
Males employ multiple mating strategies during the breeding season, but we know little about how males choose one strategy or another, or the energetic consequences of these different strategies. By tagging whales engaged in these different behaviors, we can more precisely quantify the energetic costs of these breeding strategies.
Another big accomplishment for 2025 was testing new methods to use modified CATS tags to record humpback whale heart rate. We collaborated with Dr. Angelo Torrente (Institute of Functional Genomics, University of Montpellier) and Dr. Andres Fahlman (Global Diving Research SL) to refine methods for deploying heart rate tags on humpback whale mothers and calves. Heart rate is a direct physiological measure that can help us measure stress, energy expenditure, and potential illness. Heart rate is difficult to study in large wild cetaceans, but Angelo and Andreas are at the forefront of developing this tag technology. We are excited about continuing this collaboration in 2026, and get valuable data on heart rate across whales of different age classes and behavioral states.
Acknowledgements
We want to acknowledge the significance of koholā (humpback whale) within Hawaiian culture as ʻaumākua and manifestations of Kanaloa. We use minimally invasive techniques and undergo a rigorous permitting process in order to interact with whales. We are very grateful to be able to study them and contribute to their conservation and protection.
The MMRP is grateful for our partners, collaborators, and funders, who make this fieldwork possible! We would like to thank the MMRP field team and Pacific Whale Foundation, for their invaluable assistance with tag data collection for this project. We would like to thank all of our funders for the 2025 season, including government funding from: Office of Naval Research, United States Pacific Fleet Environmental Readiness Division, U.S. Navy's Living Marine Resources Program, DoD’s Defense University Research Instrumentation Program; corporate support from: Young Brothers, Dolphin Quest; and private philanthropic funding from: JP and Dalia Maheu, Denise O'Leary and Kent Thiry, Benjy Garfinkle, Brion Applegate, and Kristin and Larry Link. All data was collected under appropriate NOAA NMFS permit (no. 27548) and university IACUC protocols.