WHY DO HUMPBACK WHALES SING?
The reason why male humpback whales sing remains a mystery. Since the early 1980s, Whale Trust researchers have been following, recording, and tracking humpback whale singers off the coast of Maui, Hawaii.
There are three primary hypotheses that have been proposed to answer this question: 1) to attract females; 2) to display dominance or status to other males; and 3) as a measure of association between males. While the first two hypotheses seemed plausible initially, they have not been substantiated by scientific research and contain inherent flaws.
Hypothesis 1: Attracting Females
- Description: This hypothesis posits that male humpback whales sing to attract females for mating purposes. It suggests that the complexity and quality of a male’s song may serve as an indicator of his fitness and ability to reproduce successfully.
- Limitations: There is currently no scientific evidence that females are attracted to and join singers. We know that males regularly join male singers, and individual differences in the song (likely the basis for female choice) have not been discerned yet.
HYPOTHESIS 2: DOMINANCE OR STATUS DISPLAY
- Description: This hypothesis proposes that humpback whale songs function as a form of dominance or status display among males. It suggests that males use their songs to establish and assert their rank within a group of whales, potentially influencing their access to mates.
- Limitations: Research has shown that singing leads to a range of male-male interactions, but differences in the song necessary to determine status have not been found. In fact, the opposite is true, song similarity is a key characteristic of song. Changes in song composition are not consistent with typical mammalian displays of individual status.
However, while the first two hypotheses have not provided definitive answers, the third hypothesis, developed and published in 2006 by Whale Trust researchers, introduces a new perspective on the function of humpback whale songs.
HYPOTHESIS #3
THE WHALE TRUST SONG HYPOTHESIS
Over the years, Whale Trust researchers have conducted studies on singers that provide insight into the function of humpback whale song. These include determination of the sex of singers (all males), the sex of whales that join singers (all males), and the study of interactions of singers and ex-singers with other social groups including females.
This hypothesis states that the song may serve as an index of association between males – and may facilitate a degree of cooperation in mating situations.1 This proposal suggests that the changing nature of the song (with all singers in a region singing the same version at any one time) provides a measure of geographic associations between males and a means of organizing male relationships during the breeding season. In turn, this may govern the male cooperative or competitive interactions when around females.
Testing the Song Function Hypothesis
This work involves testing predictions to determine if this hypothesis is useful or not. For example, if it is correct:
Prediction 1: The song should be more similar the closer the males are to each other2;
Prediction 2: Whales should respond differently to similar songs than they do to different songs;
Prediction 3: Some degree of cooperation amongst males should be apparent in interactions around estrous females.
Whale Trust is currently addressing each of these with new studies.
Key Whale Trust Findings to Date
Prediction #1: The song should be more similar the closer the males are to each other.
The Pan-Pacific Song Study described in a 2014 study compared humpback whale songs from the Philippines, Japan, Hawaii, and Mexico.2 The findings are consistent with the idea that song is more similar in regions that are closest to each other and more different at greater distance from each other.
NEW STUDY LAUNCHED: A new 3-year study underway in 2023 is expanding the number of study sites collecting songs throughout and allowing for real-time comparison. Songs are being collected from 10-14 sites including the Philippines, Japan, Hawaii, Alaska, British Columbia and Mexico.
The research collaborators include in Japan, Manami Yamaguchi in Ogaswara (Ogasawara Marine Center) and Nozomi Kobayashi in Okinawa (Okinawa Churashima Foundation); Jo Marie Acebes in the Philippines (Balyena.org); Jorge Urban in Mexico (Universidad Autónoma de Baja California Sur, La Paz) and Oscar Frey in Mexico (Deep Blue Conservancy); Joelle De Weerdt in Nicaragua (Association Elis); Chris Gabriele in Alaska (Glacier Bay National Park); and various other biologists in British Columbia from Fisheries and Oceans Canada.
Prediction #2: Whales should respond differently to similar songs than they do to different songs. This hypothesis was tested using playback experiments to play back similar and different songs to individual singers. Findings showed that singers were more attracted to similar songs (their own song) than songs from a different region.3
Prediction #3: Some degree of cooperation amongst males should be apparent in interactions around estrous females. Anecdotal observations suggest this type of cooperation amongst males may occur and a study to document and measure male-male interactions around an estrus female is planned.
To learn more about Whale Trust current research projects, visit our Current Song Research page.
- Darling, J.D., Jones, M.E., and Nicklin, C.F. 2006. Humpback Whale Songs: Do they organize males on the breeding grounds? Behaviour. 143: 1051-1101. (Download PDF)
- Darling, J.D., Acebes, J.M.V., and Yamaguchi, M. 2014. Similarity yet a range of differences between humpback whale songs recorded in the Philippines, Japan and Hawaii in 2006. Aquat Biol. 21, 93-107. (Download PDF)
- Darling, J.D., Jones, M.E., and Nicklin, C.F. 2012. Humpback whale (Megaptera novaeangliae) singers in Hawaii are attracted to playback of similar song. J. Acoust. Soc. Am. 132(5). (Download PDF)
