Written by Gussie Hollers
This February, the MMRP tagging team (Lars, Gussie, and Will) reunited with Andy Szabo from the Alaska Whale Foundation to deploy Customized Animal Tracking Solutions (CATS) suction-cup tags on humpback whales for our research on their behavior and bioenergetics. This field season looked pretty different from our past four field seasons because of the devastating wildfires that swept through Lahaina in August of 2023. Members of our lab have spent every winter since 2019 living and working out of the Lahaina harbor, and we are devastated for the families who lost their homes and loved ones in the fire. After the loss of the Lahaina harbor, we decided to transition our fieldwork base this year to the Kona coast of Hawai’i Island, due to its large number of whales and light winds.
A humpback whale breaching off the Kona coast of Hawaiʻi Island
Why the data is collected
This data is invaluable for our lab’s larger project quantifying humpback whale bioenergetic demands in the face of climate change and shifting prey availability. Martin has been collecting body condition data from Unoccupied Aerial Systems (UAS; drones) for over five years, which tells us how much energy these humpback whales are using over monthly and yearly scales. Using CATS tags, we are now able to collect and analyze video and movement data to look at fine-scale individual level energy budget and metabolism. By combining UAS and tag data, we are able to get a much clearer picture of how individual whales are using and expending energy, and model how climate change and human disturbance could affect those individual energy budgets. We can then scale up those effects on energetic budgets to the population level, and model how the population might grow or shrink under different climate scenarios.
A humpback whale mother and calf seen from above. The calf has a CATS tag attached with suction cups to its back
For the first chapter of my PhD dissertation, I will be comparing energy budgets of humpback whale mothers and calves in Hawaiʻi. The winter season spent by humpback whales in Hawaiʻi is especially important for mothers and calves. Calves must grow large and strong enough to survive the spring migration, and mothers must retain enough weight while fasting and lactating, in order to also survive the spring migration. From Martin’s UAS measurements we can estimate the amount of body mass mothers are losing and calves are gaining over the course of their time in Hawaiʻi, but we do not know the breakdown of how this energy is being spent. Better understanding how this energy is partitioned will help us model the energetic consequences of behavioral changes due to ecosystem disturbance. How much energy is being spent on body maintenance and metabolism? How much energy is being spent on movement? How much energy is spent while the whale is resting versus while itʻs traveling? To answer these questions, we decided we needed to deploy more tags on mother whales this field season, to match the 27 tags we had previously deployed on calves. We also wanted to deploy more tags on the whales overnight to better understand their daily behavior cycles.
A calf swimming past the head of its mother filmed from the CATS tag attached to her back
Our goals and challenges
We deployed 26 tags this year, the most we have ever deployed in one season! We deployed ten tags on mothers, 12 on calves, one on a juvenile, and three on adult males, for a total of 118 hours of data. The calm water and large coastline of Hawai’i Island allowed us to spend twelve out of fourteen days on the water, often working into the late afternoon and evening. We accomplished our goal of deploying ten tags on mother humpback whales. We were slightly less successful in our goal to get tags to stick overnight on calves. We deployed four tags on calves after 3:00 pm, but only one tag stayed on overnight. Our hypothesis was that calves breach more often in the evenings, leading to a greater likelihood of the tags falling off. Calves also often rub their backs against their mothers, causing the tags to fall off.
Deploying a CATS tag on the back of a calf near Kīholo bay
One of the goals of this field season was to train me to become proficient enough at tag deployment so that I can successfully tag whales in Alaska this summer for the third chapter of my Ph.D. project. Andy, Lars, and Will have many years of tagging experience, and I am so grateful to be able to learn from them. Will has worked hard over the past year to teach me the data processing and analysis side of working with tags. During this field season Lars showed me how to deploy the tags, and Andy gave me advice on how to work with the boat driver to approach the target whales. I successfully deployed five tags, and am leaving this season feeling confident in tag prep and retrieval, and growing in confidence in tag deployment.
GoPro footage of me deploying a CATS tag on a yearling calf
Another goal of our field season was to collect samples of humpback whale blows for Nelmarie Giovanetti’s project studying the presence of cetacean morbillivirus in the North Pacific population of humpback whales. Morbillivirus, a respiratory disease in the same family as human measles, is one of the most significant threats to cetaceans worldwide with high infection and mortality rates. This season, we tested out a method of collecting blow samples by extending a long pole into the blow cloud as the whale surfaces and breathes. We got five blow samples this season from adult males and females. We are looking forward to hearing about Nelmarie’s results, and continuing to work with her to optimize the methods.
Tag retrieval was overall easier this season compared to previous years off Maui. Out of 26 tags deployed, we only had two difficult retrievals. Those tags were deployed on a mother and yearling calf pair farther north, offshore of Waikoloa. Overnight, the tags floated quickly past the northern tip of the island into the channel between Hawai’i and Maui. We were able to retrieve one tag the next day in 13 foot swell and 30 knot winds, but it was unsafe to continue on into the wind to retrieve the second tag. Luckily, twelve days later, the tag came back towards the Kona coast in a gyre. We are so grateful for our partner Colin Cornforth at Captain Zodiac who took MMRP lab members Lewis and Kyleigh 60 miles offshore to retrieve the tag!
Left: the GPS track of tag H2 floating offshore of Hawaiʻi Island
Right: The brave retrieval crew! From left to right: Colin Conforth, Kyleigh Fertitta, Lewis Evans, Jason Lafferty
Notable encounters
The humpback whales seemed to prefer the shallower waters of the northern Kona and Kohala coast, but the much deeper waters to the south of Honokohau harbor allowed us the chance to opportunistically study other species such as sperm whales, pilot whales, and false killer whales. Based on tips from other Kona boat tour operators, one day we found a group of sperm whales about four miles offshore of Kealakekua bay. We collected UAS body size data, photo-ID, and fecal samples. It was my first time seeing a large pod of female and juvenile sperm whales! They rest at the surface generally longer than humpback whales, and typically dive to 1,000-2,000 meters depth hunting squid.
Drone footage of three sperm whales resting at the surface, filmed by Lewis
On our second to last day on the water, we encountered a group of whales who were especially relaxed and curious about our boat. They were so close we could take photos and videos with our GoPro cameras. The group was made up of a mother, escort, and large yearling calf. It is rare to see a yearling calf with its mother in Hawaiʻi, usually calves wean and separate from their mothers before or shortly after the fall migration back to Hawaiʻi. We were able to put tags on both the mother and yearling calf, and confirmed that the calf was still nursing over a year later - this is a very interesting observation and something we want to dig further into.
A photo taken with Fionaʻs GoPro from the side of the boat of the mother and yearling calf. The large calf is below the mother
CATS tag footage of the yearling calf nursing from its mother. Its mouth is open on the left, and its eye is on the right.
Acknowledgements
We want to acknowledge the significance of koholā (humpback whale) and palaoa (sperm 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 so grateful for our partners, collaborators, and funders who make it possible for us to study these animals safely and responsibly. Our collaboration with Alaska Whale Foundation has allowed us to collect the largest body condition database on humpback whales in the world with over 10,000 images processed from ten months out of the year. Even though we were working off Kona this year, we are grateful that Jens Currie and Pacific Whale Foundation were willing to assist us with retrieval if the tag drifted close to Maui. We are thankful for the help from tour operators on the Kona coast in locating rare species and educating the public about cetacean research. This was the first season for the MMRP’s new RHIB boat, purchased with funding from the ONR’s Defense University Research Instrumentation Program (DURIP) and it was a near perfect platform from which to deploy tags and launch drones. All research was conducted under NOAA permit 21476 and IACUC approvals.