Humpback whales (Megaptera novaeangliae) are a species of baleen whales, or Mysticetes, that migrate thousands of miles seasonally between feeding grounds and breeding grounds each year to reproduce and give birth to calves in a safe and warm environment (Calambodikis et al. 2001). You may have seen them on National Geographic, social media, or even from a whale watch boat. You can identify them through the unique pattern on the underside of their fluke, or tail. They might playfully slap their flukes and pectoral fins in the water, and when they take a breath, their blow is heart shaped! Those that are lucky enough to interact with humpbacks cannot deny their curious nature and gentle demeanor- they are absolutely wonderful creatures.
In Hawaii, 60% of the north Pacific stock of humpback whales gathers around the islands to breed and give birth. Humpbacks, who filter food lower on the food chain through their baleen plates, do not eat the entire time on the breeding grounds. That is up to 4 months of fasting, all while supporting another life either in the womb or through lactation, which is pretty amazing. All of this fasting is supposed to be worth the chance to pass on their genes and have offspring. So, how do they do that?
Humpback whale choir
Humpback whales sing a unique song only on the wintering grounds and exclusively by males. Scientists have long assumed this song is used to attract females, but overall there are no definite conclusions. Some scientists believe the song is used for navigation, although it is understood that baleen whales don't use echolocation to the same extent as toothed whales.
Regardless, humpback whale song is one of the most haunting and exquisite types of sound. It propagates at a frequency between 80-24,000 Hz and they sing at depths of 10-25 meters. You have to dive down if you want to hear it. Because sound travels far and easily underwater, humpbacks that are singing can be heard by divers miles away. I had the pleasure of hearing them sing season, and it was magnificent.
Nature of the Song
Humpback whale song is culturally transmitted and regionally distinct. This mean is it passed down by generations of the species through learning and varies by wintering grounds. All males sing the same song, but that song changes through time. This means that humpback whale song is a learned acoustic process, and males have to observe the evolutionary changes from other males. Furthermore, the song never repeats itself and never ends. The acoustic signatures are distinct and never identical to past signatures. The male stops singing at the end of the breeding season and travels back to feed for the summer. Once returning to the breeding grounds the following winter, he picks up right where he left off in his song.
The physical behavior of the singer is intriguing. In the northern hemisphere, humpback whales only sing upside down, or facing toward the equator. Hawaiian humpback whales suspend themselves vertically between 0-75 degrees. In the southern hemisphere, humpback whales sing upright and point their rostrum toward the equator.
Is the humpback whale song in trouble?
Although the details of song function are understudied, there is a clear ecological benefit to male singing. It requires a lot of energy expenditure to sing for hours on end, and there must be a pay off. Wintering grounds for humpbacks are for mating and calving, and humpback whale song is likely essential for the survival of the species. The Hawaiian population of humpback whales is threatened, and lower numbers in the region suggest it is decreasing.
Noise pollution is an ongoing conservation threat to marine life in our oceans. Between gigantic shipping containers, underwater explosions for offshore drilling, and military exercises that use SONAR, marine species that utilize the underwater soundscape for their survival are at serious risk. Sound travels far and wide in our ocean, and the concert of humpback whale singers cannot be heard. A boat engine will easily drown out the mating song of a humpback, which would heavily impact the reproductive success of that individual. In turn, this will impact the reproductive success of the population.
Minimizing noise pollution is essential for healthy whales and a healthy ocean. Their lives depend on it. Innovative technologies are creating quieter engines, and regulations can be implemented to reduce shipping speed and sound. Federal agencies can monitor military impacts on our underwater soundscape, if we speak up and let our representatives know it matters to us. Similarly, offshore drilling operatives are creating deafening explosions that not only drown out songs and echolocation, but are often so harmful that dolphins and whales strand themselves to escape the pain. Our reliance on oil is directly destroying these populations.
We can do something about all of this. We can call our senators, we can spread this information, and we can make sure we are heard by our governments. We can reduce our oil dependence on an individual level through saying no to plastic, educating ourselves and others from where these issue originated, and changing our lifestyles. We can organize, collaborate, and come together to speak up for these animals. At some point, we have to realize that if we don't do it, maybe no one will. We must be their voice, because they cannot be heard.
Au W. Pack A. Lammers M. Herman L. Deakos M. Andrews K. 2006. Acoustic properties of humpback whale songs. Acoustical Society of America 120(2): doi10.1121/1.2211547. x
Calambokidis J. Straley J. Herman L. Cherichio S. Salden D. Urban R.J. Jacobsen J. Zeigesar O. Balcomb K. Gabriele C. 2001. Movement and populations structure of humpback whales in the north Pacific. Marine Mammal Science 17(4): 769-794. x