Humpback whales move during the day singing offshore, research reveals

The song of humpback whales dominates the marine soundscape during the winter months off the coast of Maui. However, despite decades of research, many questions regarding humpback whale behavior and song remain unanswered. New research has revealed a daily pattern where whales move their song away from shore throughout the day and return to shore in the evening.

The findings were conducted by the University of Hawaii, in partnership with NOAA’s Hawaiian Islands Humpback Whale National Marine Sanctuary, and published in Royal Society Open Science.

“Singers may be trying to reduce the chances of their song being drowned out in the nearshore cacophony when whale numbers are high,” said Anke Kügler, lead author of the study and doctoral student in the graduate program. in marine biology at UH Mānoa at the time of the research. “Additionally, we have documented humpback whales moving closer to shore at sunset, perhaps to avoid the chorus of other animals offshore.”

Using a combination of underwater listening devices and visual surveys, the research team was able to track both the physical movements and acoustic patterns of whales in the high-density breeding grounds found in Hawaii .

“This dynamic movement of singers between land and sea could aim to increase the effectiveness of whales’ acoustic display, ensuring that other whales hear their songs,” said Marc Lammers, co-author of the study. and a research ecologist with NOAA’s National Islands Humpback Whale National. Marine sanctuary.

“This is the first effort of its kind, to our knowledge, in which we have used specialized acoustic sensors to locate individual singers relatively close to shore to understand daily variations in the distance to shore of these coastal singers, their spacing and their movement behavior,” Kügler said. “This helped contextualize the visual results and overcome some of the limitations of terrestrial visual observations of movement.”

The song of humpback whales is presumed to play an important role in reproduction. The new findings highlight the importance for male singers of an environment teeming with acoustic agitation. Using their approach, the team identified potential drivers of daily shore-to-shore migrations: coastal environments too populated with whales during the day and offshore areas too noisy with the chorus of other animals in the evening.

“Discussions about marine mammal-related noise pollution have been dominated by concerns about anthropogenic noise,” Kügler said. “Potential acoustic masking from natural sources, including a whale masking another whale’s song, has been largely overlooked. By exploring possible drivers of the observed patterns, we add to our understanding of how animals who depend on acoustic signals adopt behavioral strategies to mitigate the masking of noisy environments.

Humpback whales are ecologically, economically, and culturally important in Hawaii, and their song is iconic around the world.

“It is our collective kuleana (responsibility) to be stewards of the koholā (humpback whales),” Lammers said. “This and future work contributes to the sanctuary management plan by developing and implementing critical research on humpback whales and their habitats to help maintain a healthy and sustainable population.”

In addition to Kügler and Lammers, study co-authors include Adam Pack, professor of psychology and biology at UH Hilo, founder and director of the UH Hilo Marine Mammal Lab and co-founder of the LOHE Bioacoustics Lab; and Aaron Thode and Ludovic Tenorio-Hallé of the Scripps Institute of Oceanography, University of California.