HUMPBACK WHALE SONG
The song of the humpback whale is a loud, complex series of sounds repeated over and over. It occurs primarily (although not exclusively) during the breeding season, is sung only by males, and its composition changes over time. All singers in a population sing fundamentally the same version of this changing song at any one time.
Why humpbacks sing remains unknown.
HISTORY OF SONG RESEARCH
Whale Trust researchers have been following, recording, and tracking humpback whale singers off the coast of Maui since the mid-1970s. Our research program has investigated song function through study of the behavior of singers and their interactions with other whales. Our results to date have indicated that singing attracts other adult males, not females, and the resulting male-male interactions are usually non-agonistic (that is, not competitive or aggressive).
TABLE OF CONTENTS
- CURRENT SONG RESEARCH
- DIVE DEEPER
- MAUI MYSTERY SOUNDS
CURRENT SONG RESEARCH
SONG FUNCTION IN HAWAII
Starting in the 1980s 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 (males), and the study of interactions of singers and ex-singers with other social groups including females.
More recently, we have been investigating the hypothesis that the song may, among other things, serve as an index of association between males – and may facilitate a degree of cooperation in mating situations. This work involves testing predictions to determine if the hypothesis is useful or not. For example, if it is correct, 1) the song should be more similar the closer the males are to each other, 2) whales should respond differently to similar songs than they do to different songs, and 3) some degree of cooperation amongst males should be apparent in interactions around estrous females. We are addressing each of these with studies.
SONG COMPARISONS OF THE NORTH PACIFIC
Well known for migrating across entire ocean basins, whales bring countries and cultures together. For years now, Whale Trust has partnered with colleagues from across the Pacific Ocean to monitor and track similarities and differences in humpback whale song.
The first stage of this study compared same season songs (2006) from Japan, the Philippines, and Hawaii and found that while the songs shared some common themes, those recorded in the closer regions of Japan and the Philippines were far more similar to each other than to the more distant samples recorded in Hawaii. (Darling, Jones, & Nicklin, 2006)
This led to a much larger, 3-year, four location study. From 2011-2013, Whale Trust led a collaborative project to examine and analyze the similarities, differences, and dynamics of change in the composition of songs between humpbacks in Hawaii, Mexico, Japan, and the Philippines. This study indicated – through the comparison of song composition – there is ongoing, but annually variable, mixing of humpback whale populations across the North Pacific. (Darling et al., 2019)
A new collaborative comparison of songs across the North Pacific began in 2023 and, continuing through 2026, will again compare of songs from Central America, Mexico, California, British Columbia, Alaska, Hawaii, Northern Japan, Southern Japan, and the Philippines, including subregions within the larger locales. For example, it will look at three different locations within Mexico and three within southern Japan. It includes study of season changes of the song in one location and songs from fall feeding grounds in northern latitudes.
Our partners include:
- Manami Yamaguchi (Japan; AFFILIATION)
- Nozomi Kobayashi (Japan; Okinawa Churashima Foundation)
- Jo Marie Acebes (Philippines; BALYENA)
- Jorge Urban (Mexico; University link)
- Oscar Frey (Mexico; Deep Blue Conservancy)
- Joelle De Weerdt (Nicaragua; Vrije Universiteit Brussel)
- Chris Gabriele (USA; Glacier Bay National Park)
HOW DO SINGERS RESPOND TO PLAYBACK RECORDINGS OF HUMPBACK WHALE SONGS?
Whale Trust researchers conducted playback experiments that involve playing back similar and different songs to singers on the Hawaiian breeding grounds. The purpose, through measuring their responses, is to increase our understanding of how songs may govern interactions between whales on the breeding grounds. Preliminary results indicated that singers responded by approaching similar songs (current songs in Hawaii) but did not approach foreign songs, song completely different than the Hawaii song (e.g., song from Central Africa). ADD LINK TO PAPER.
SONG STRUCTURE & COMPOSITION / HAWAII’S HUMPBACK WHALE SONG
The humpback whale song is a series of sounds that typically lasts 10-15 minutes and is repeated over time. The song consists of several different themes (often four to six) sung in a continuous loop. Each theme is composed of sound units distinctly arranged as a phrase, which is repeated for several minutes. The singer progresses through each of the themes (all with different combinations of units/phrases) until he has worked through the entire song. If the song has four themes, the singer will sing themes 1, 2, 3, 4, usually surface to breathe, then dive and start all over again. A song session (continuous singing) can last hours.
In the graphic above, the song themes are given different colors. All singers in the population follow the same pattern of theme composition and progression. Even the amount of time spent on one theme is similar. During this period (January, 2005) about 70 percent of the Hawaii song consisted of theme 3 (yellow).
WHALE SONG SPECTROGRAPHS
This whale would sing each of these themes in orders shown, surface to breathe (after blue theme) then dive and begin again with the pink theme. Click on the audio-files below to hear the sound of the phrases in each theme.
UNIQUE CHARACTERISTICS OF HUMPBACK WHALE SONG
The humpback song is unique in that it gradually changes in composition as it is being sung. That is, small changes in song units will change phrase composition and, in turn, entire themes (phrase ‘aaab, aaab’ in Theme 1 may change over time to ‘ab, ab’ and then eventually drop out of the song altogether). Yet all the singers in a population sing the same version of the ever-changing song at any one time. It is not known how this is achieved.
VARYING RATES OF HUMPBACK WHALE SONG CHANGE
The rate of song change varies – the reason is unknown. Humpback songs studied in Bermuda and Hawaii changed gradually, with the entire song composition turning over in four or five years. However, song studies in the South Pacific observed more rapid changes, with the potential for whales to adopt an entirely new song from one year to the next.
MAUI MYSTERY SOUNDS
Imagine hearing a heartbeat-like sound in the ocean, but not knowing the source. These were first recorded near a surface active group off Maui in 2005 – then it was the better part of a decade of listening before a second good recording was made. On this exceptionally quiet calm day in 2013 these sounds were recorded within a few meters of a pair of humpback whales, with their behavior preserved on video. Convincingly, the sounds increased in volume as the whales got closer and became softer as the whales swam away. This led to a publication describing these sounds for the first time. ADD LINK TO PUBLICATION
Examples of these low frequency pulses of sound are below.
One of the questions that has arisen is why these sounds are not heard more often. At least part of the answer lies in just how difficult they are to hear, even under perfect listening conditions. The sounds at 40Hz are only slightly above the lower threshold of human hearing (20Hz) and are easily masked by background ocean sounds such as waves and wind, other whale sounds, and by boat noise. Another reason is that there are not that many people listening.
If verified, and these sounds are indeed another communication channel for humpback whales beyond the familiar song and social sounds, it could completely change how we view and interpret whale behavior on the breeding grounds.
Below are spectrographs (pictures of sounds) that illustrate these bouts of low frequency pulses (sounds). The spectrograph displays frequency (how high or low the sound is) on the vertical axis and time on the horizontal axis. The degree of boldness of the sound pattern indicates the relative density or closeness of the sound to the hydrophone. The pulse patterns are typically heard around 40Hz. Humans can hear from about 20Hz to 20,000Hz, so these sounds approach the lower threshold of our hearing.
Use earphones, or connect your computer to the biggest woofer you can find. These are bass sounds, so they can be difficult to hear amongst all of the other humpback whale sounds (both song and social sounds) that you hear clearly.
Watch the cursor on the spectrograph as it passes over the bright yellow sounds to know when you should be hearing these lower frequency sounds. Listen for a series of pulses: babum, babum, babum. Think heartbeat.
Example 1: February 12, 2005
Recorded off Maui near a competitive or surface-active group of 8 whales (usually comprised of one female and multiple males). During this encounter lasting 70 minutes, the low frequency pulses were present on 8 of 9 recording tracks. One of the tracks illustrated below.
Example 2: March 8, 2013
Recorded over a 22-minute period while a pair of adult whales, a male and a female, circled around our research boat. The low frequency pulses were heard during the first 13 minutes of this recording; none were heard after that.
The bouts of pulses ranged from a few seconds to over 90 seconds in duration with variable gaps in between them. The increase and decrease in intensity is dependent on the position of the whale relative to the hydrophone.
One of the most exciting parts of this study was the ability to place the sounds within a behavioral context. Play the video below to see the context in which recorded these sounds on March 8, 2013.
This video shows a male and female pair circling our research boat. The hydrophone cable is just visible hanging from the corner of the boat.
Note: the sounds and video are not synchronized, that is the pulse recording and video were taken with the same whales over the same 20-minute period but independently.
Video Credit: Jason Sturgis/Whale Trust. NOAA permit #13846. Courtesy “Humpback Whales”, Pacific Life and MacGillivray Freeman Films.