Humpback whales have moved their singing rituals away from shorelines

In the serene waters off Maui during the winter months, the melodic singing of humpback whales fills the marine soundscape.

Despite extensive research spanning decades, many aspects of humpback whale behavior and their complex singing remain enigmatic.

Recent research, however, has begun to unravel some of these mysteries, offering new insights into the daily patterns of these majestic creatures.

Decoding humpback whale songs

The study, spearheaded by the University of Hawaiʻi in collaboration with NOAA’s Hawaiian Islands Humpback Whale National Marine Sanctuary, observed an intriguing daily movement pattern among the whales.

These gentle giants tend to drift away from the shore during the day, only to return as evening approaches.

This pattern of migration is not just a random movement but appears to be a strategic choice by the whales.

Anke Kügler, the study’s lead author and a doctoral student in the Marine Biology Graduate Program at UH Mānoa at the time of the research, shared her insights.

“Singers may be attempting to reduce the chances of their song being drowned out among the cacophony nearshore when whale numbers are high,” Kügler explained.

She further noted that the whales’ movement towards the shore around sunset might be to avoid the offshore evening chorus of other marine animals.

Learning how and when humpback whales sing

The methodology behind this humpback whale research was as innovative as its findings.

By employing a combination of underwater listening devices and visual surveys, the team successfully tracked both the movements and the acoustic patterns of the whales in their high-density breeding grounds.

This dual approach allowed for a comprehensive understanding of the whales’ behavior.

Marc Lammers, co-author of the study and a research ecologist with NOAA’s Hawaiian Islands Humpback Whale National Marine Sanctuary, highlighted the significance of this movement.

“This dynamic onshore-offshore movement of singers may be aimed at increasing the efficiency of the whales’ acoustic display, ensuring that other whales hear their songs,” he said.

Localization with acoustic sensors

The study not only tracked these movements but also explored the reasons behind them. Kügler elaborated on the unique approach taken by the team.

“This is the first effort of its kind, to our knowledge, in which we used specialized acoustic sensors to localize individual singers relatively close to shore to understand daily variations in their distance from shore, their spacing, and their movement behavior,” she said.

This strategy helped the team to contextualize visual results and address some limitations inherent in land-based observations.

The song of the humpback whale, believed to be crucial for breeding, takes on new significance in light of these findings.

The study highlights the challenges male singers face in an environment bustling with acoustic activity.

Noise pollution vs. natural noise

The team identified key drivers for the whales’ daily migrations — crowded nearshore environments during the day and noisy offshore areas in the evening due to the chorus of other marine animals.

Kügler also shed light on a broader ecological issue — noise pollution. “Discussions of noise pollution related to marine mammals have been dominated by concerns over anthropogenic noise,” she stated.

The study brings to attention the potential acoustic masking from natural sources, like one whale’s song masking another’s, a factor often overlooked in previous research.

Understanding these natural drivers adds depth to our knowledge of how animals reliant on acoustic signals adapt to loud environments.

Humpback whales and Hawaiian culture

The humpback whales of Hawai‘i are ecologically and economically significant, while holding a special place in the cultural heritage of the region.

Their singing is recognized and cherished worldwide. Lammers emphasized the shared responsibility in protecting these magnificent creatures.

“It is our collective kuleana (responsibility) to be the koholā’s (humpback whales) stewards,” he remarked.

Lammers underscored the importance of such research in fulfilling the Sanctuary’s management plan, aimed at maintaining a healthy and sustainable whale population.

In summary, this research provides new insights into understanding humpback whale behavior, signaling a leap forward in our journey to unravel the mysteries of these oceanic songsters.

The full study was published in the journal Royal Society Open Science.

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