Written by Martin van Aswegen
At the beginning of each year, I head to the Maui Nui region to study the whales frequenting the shallow, calm waters of the Au’au Channel (Figure 1). Each winter, Hawaii hosts approximately 10,000 humpback whales migrating from cool, productive feeding grounds throughout the North Pacific. These migrations extend between 5,000-10,000 miles round-trip, representing some of the longest migrations in the animal kingdom. As capital breeders, humpback whales undergo distinct periods of foraging on high latitude feeding grounds and fasting during migration to warmer, subtropical breeding grounds. This means whales must maximize their energetic intake, in preparation for fasting periods lasting 3-4 months. While fasting on the Hawaiian breeding grounds, adult whales experience considerable energetic stress related to metabolic requirements and reproduction. The latter can be particularly taxing to lactating females who must navigate a fine line between providing enough energy to ensure the survival of their dependent calf while also ensuring their own energy stores are sufficient for the northbound migration.
The Marine Mammal Research Program (Hawaii Institute of Marine Biology, University of Hawaii at Manoa (UH)), through the work of Director Dr. Lars Bejder, myself, and collaborators (see below), is quantifying humpback whale behavior, growth and health in Hawaii and Alaska with the aim of developing a bioenergetic model encompassing most facets of humpback whale life. By quantifying humpback whale energetics and fine-scale behavior on both their Hawaiian breeding and Alaskan feeding grounds, the team will determine what it ‘costs’ to be a humpback whale in the North Pacific.
Figure 1. Map showing the study site (Au’au Channel) between the islands of Maui and Lanai’i. Blue lines indicate track lines of the MMRP boat surveys between January 19 and March 15.
The 2022 Maui field season represented our fourth consecutive winter studying humpback whale health in close collaboration with the Pacific Whale Foundation (PWF; Jens Currie and Stephanie Stack), University of Hawaii at Hilo (UHH; Dr. Adam Pack), Alaska Whale Foundation (AWF; Dr. Andy Szabo) and UH Marine Mammal Health and Stranding Lab (UHMMHSL; Dr. Kristi West). Since 2019, the team has assessed humpback whale health by linking morphometric measurements derived from unoccupied aerial systems (UAS; drones) with tissue samples collected through biopsy sampling. Aerial images of whales laying flat at the surface provide accurate estimates of body length and width (Figure 2), with specialized UAS altimeters ensuring accurate scaling from pixels to absolute length (i.e., in meters). Two-dimensional body width measurements are converted to three-dimensional estimates of body volume used to calculate body condition indices.
Body condition is considered a proxy for health, given it reflects an animal’s stored energy reserves at a given point in time. Biopsy samples provide a sleuth of valuable information including but not limited to stress hormones, reproductive hormones, adiposity, diet and genetics. Linking UAS-derived measurements with such biopsy-derived metrics provide the team with a comprehensive picture of how humpback whale health and stress varies within the context of migration, reproduction, and ocean productivity.
Figure 2. Schematic showing the morphometric measurements taken from a single image of a whale at the surface. Measurements include total length and body width in 5% increments along the body, totaling 19 width measurements.
Like previous years, two two-week field stints were carried out by MMRP, PWF, and UHH onboard PWF’s research vessel Ocean Protector. The two stints covered the first and last two weeks of January and March, representing early and late parts of the breeding season, respectively. Overall, the weather was excellent, with approximately 80% of available boat days spent on the water. Over these two blocks, approximately 300 whales were identified by their flukes, >400 were measured by the UAS and >160 biopsied.
Between mid-January and mid-March, we (MMRP) continued our data collection efforts with near-daily boat surveys throughout the Au’au Channel. During these trips, we collected UAS-derived morphometrics, biopsy samples and photo identification data. In early February, Dr. Lars Bejder, Dr. Andy Szabo (AWF) and Will Gough (Goldbogen Lab, Stanford University) conducted two weeks of tagging using customized animal tracking system (CATS) tags with the aim of quantifying calf suckling rates and fine-scale behavior). Tagged whales were measured with the UAS to relate body size and condition information to energy transfer and expenditure.
Between January 19 and March 14, we conducted 44 boat surveys with beautifully calm weather consistently gracing us throughout the season. During the MMRP boat surveys, we collected approximately 850 photo identification images and 1,800 whale measurements, including 605 mother-calf pairs and 590 non-calf individuals. An additional 55 biopsies were collected and linked to UAS measurements. Over the entire field season (January 5 to March 30, n=64 boat days), our collaborative effort collected approximately 2,300 whale measurements, which is more than our 2019-2021 sample sizes combined. The number of biopsies collected throughout the season totaled 211, also representing a personal best total for the team. We are currently working through the data and will provide some preliminary results in the near future, so stay tuned.
A unique aspect of this winter field season was the number of whale entanglements we were able to assist with. The MMRP team either found or responded to calls of entangled whales on three occasions in January and February with a fourth rescue effort in March alongside PWF and UHH. With specialized training, the NOAA Hawaiian Islands Humpback Whale National Marine Sanctuary (HIHWNMS) and Marine Mammal Health and Stranding Response Program (MMHSRP) lead all marine mammal disentanglement efforts in the Maui Nui region, with additional vessel support provided by local groups including but not limited to PWF and Ultimate Whale Watch. Our primary role was aerial support, with the aim of using UAS footage to gather and relay information on gear types, wrap characteristics and whale injury/condition (Figure 3). The MMRP team either found or responded to calls of entangled whales on three occasions in January and February with a fourth rescue effort in March alongside PWF and UHH in PWF’s Ocean Protector.
January 26, 2022: Around 09:30 in the morning, we responded to a call of an entangled whale off Olowalu which turned out to be a young juvenile whale, likely recently weaned based on its body length and body condition. Always on the surface, the whale appeared to be dragging around a heavy weight with its activity level fluctuating between franticly fast and exhaustively slow. From the air, there looked to be one wrap around the tail stock of the whale with the entanglement appearing relatively recent. Following a period of information gathering (reviewing footage from the air and underwater (thanks to Ultimate Whale Watch and the HIMB shark researchers)) and careful approaches, the juvenile was finally cut free around mid-afternoon.
February 4, 2022: As I was flying the UAS back to the MMRP boat during a routine research flight, I sighted a whale with what looked to be line trailing behind it. Once I was hovering over the whale, we confirmed it had line wrapped around its left pectoral fin. While waiting for the folks at the HIHWNMS/MMHSRP to arrive, our primary role was to track the whale and continue assessing the entanglement and whale condition. The whale appeared to be in a relatively emaciated condition with some cyamid (whale lice) coverage but was travelling at a considerable speed with breath holds of approximately four minutes. Once the disentanglement experts arrived and assessed the situation, an attempt was made to attach buoys to the trailing line to tire the whale sufficiently for a safe approach. Unfortunately, the line trailing from the whale was disintegrating and snapped with no way of knowing whether the whale was free of line or if the line simply gave way before the wrap on the pectoral fin. The status of this whale is currently unknown.
Figure 3. Aerial images of each of the whales entangled in January, February and March 2022, including a juvenile on January 26, mature adult on February 4, lactating female on February 14 and mature male on March 15.
February 14, 2022: With a beautiful day forecast, we started collecting UAS measurements early in the morning when a call came through from PacWhale Eco Adventures whale watch vessel Ocean Explorer. A mother whale was entangled with gear wrapped around her head and appeared to be resting in front of Lahaina Harbor. Diligently spotted and reported by catamaran Trilogy V, the NOAA disentanglement team were enroute from Maalaea Harbor – about one hour away. The MMRP crew conducted multiple UAS flights to determine the body condition of the mother and her dependent calf. The aerial footage in conjunction with underwater footage provided a clear picture of how the gear was wrapped around the whale’s head. The NOAA disentanglement team arrived, assessed whale behavior and patiently waited for the right moment before successfully cutting the line and freeing the mother whale.
March 15, 2022: Towards the end of our field day with PWF and UHH, an entangled whale was spotted and reported by one of the PacWhale Eco Adventures vessels. There were multiple whales in the area which made it challenging to identify and track the entangled whale. However, once located, we were able to track the whale’s movements, assess the whale’s condition and determine the entanglement characteristics. The entangled whale appeared to be an escort associating with a mother-calf pair. By tracking the whale’s underwater behavior/movements from the air, we were able to relay valuable information to the disentanglement boat who only had the difficult task of approaching and freeing the whale with only 1-2 breaths between dives. Eventually, everything aligned when the NOAA vessel approached and successfully cut the line before the whale was able to react.
MMRP in conjunction with key research partners, have been documenting the occurrence and impacts of entanglements and vessel collisions since 2018. Using a suite of research techniques, we are exploring how these entanglements impact the energetics of whales already under considerable energetic stress. The MMRP team was in awe of how professional, patient, and skilled the disentanglement responders were on each of the above occasions and were proud to play a small role in each of the disentanglement efforts.
We would like to thank the HIHWNMS, MMHSRP, local operators (Ultimate Whale Watch, PacWhale Eco Adventures, Trilogy V, Napali Explorer III), Pacific Whale Foundation, U.S. Coast Guard, NOAA Office of Law Enforcement, NOAA Corps and Cardinal Point Captains.
A big thanks to all those who helped make the 2022 Maui season so successful: Lars Bejder, Aude Pacini, Stephanie Vlachos, Jens Currie, Stephanie Stack, Adam Pack, Abigail Machernis, Grace Olson, Florence Sullivan, Lizzie Beato, Lewis Evans, Jessie Hoffman, Paul Schofield, Sonja Feinberg, Javier Garcia, Hannah von Hammerstein, Ava Sergio, Kealana Almeida, Leah Fogel, Abigael Jacka, Liah McPherson, Laule’a Blanco, Josh and Shanel Guth, Chrissy Lovitt, Emma Nelson, Alex Warham, Kyle McBurnie, HIHWNMS, MMHSRP, National Marine Sanctuary Foundation, UH Graduate Student Organization.
Like the whales, my focus has shifted to Alaska where I will be collecting measurements of whales from mid-May to the end of September. This will be the fifth consecutive year of data collection in close partnership with Dr. Andy Szabo and the Alaska Whale Foundation.
Stay tuned for my next update from the temperate rainforests of Southeast Alaska!
Until next time.
All research activities were conducted in accordance with NOAA permits 21476-01, 21321, 20311-01, 14585, and 19655. UAS activities were conducted in compliance with FAA Part 107 regulations.
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