The best musicians also happen to be the largest.
Growing from 13 to 16 meters in length and weighing in at 36 metric tons (Clapham, 2000), humpback whales are notorious for their large size, but despite their appearance, these mammals produce wavelengths that are responsible for the ocean’s most alluring and intricate sounds. Situated at the beginning of the trachea, the humpback’s call begins in a U-shaped fold in the larynx adjacent to a laryngeal sac (Hauer-Jensen, 2018). There rests a valve-like structure that regulates intrathoracic pressures and generates frequencies in many aquatic mammals (Laitman & Reidenburg, 2007). Through the contraction of the laryngeal sac and the movements of supporting arytenoid cartilages, vibrations are then expelled out of the resonant space and into the lumen of the sac before finally being released into the ocean.
Figure 1: Spectrogram of humpback song with each panel representing five minutes of sound. The solid line marks the measurement of song length. The dotted line marks the measurement of minutes from the start of the last ping to the end of the song (Fristrup, 2022).
These frequencies can range from 20 to 24,000 Hertz (Hauer-Jensen, 2018) and can extend up to 4 kilometres (Dunlop, 2019), overlapping both natural and synthetic noise. To the human ear, these vocalizations are perceived through a series of clicks, whistles, and pulsed calls, similar to traditional music. These sounds are believed to be used predominantly for navigation and prey detection, with the effused waves bouncing off the target before oscillating back. This helps whales identify nearby surroundings as well as the approximate distance between them. During mating season, it is the male humpback whales that are observed to emit the most complex music, ranging from 30 to 5000 Hz, with harmonics up to at least 24000 Hz (Marchand, 2022). This serves as a direct line of communication for mate attraction, distress, aggression, and many other purposes to counter the ocean’s ongoing cacophony. This attribute varies per region as previous studies have discovered a Lombard response exhibited in whales, giving them the ability to adapt the source levels in their sounds in response to fluctuating levels of wind noise (Guazzo, et al., 2020).
Educating ourselves on the characteristics of humpback whales opens up a birth of possibilities, exploring themes of whale behavior and flow of oceanic traffic to better understand migration. We can use this to determine if an increase in aquatic frequency from shipping traffic obstructs a whale’s wavelength, directly reducing the reproductive success of males, and dictating population growth (Kobilinsky, 2023). Using what we already know, and hope to know about the qualities of humpback whales, we can better understand the inner complexities of the baleen whale, and foster a new generation of aquatic life that we can hope to value, cherish, and sustain.
References
Dunlop, R.A. (2019) ‘The effects of vessel noise on the communication network of humpback whales’, Royal Society Open Science, 6(11), pp. 1–12. doi:10.1098/rsos.190967.
Fristrup, K.M., Hatch, L.T. & Clark, C.W., 2003. Variation in humpback whale (Megaptera novaeangliae) song length in relation to low-frequency sound broadcasts. The Journal of the Acoustical Society of America, 113(6), pp.3411-3424.
Guazzo, R.A., Helble, T.A., Alongi, G.C., Durbach, I.N., Martin, C.R., Martin, S.W., & Henderson, E.E., 2020. The Lombard effect in singing humpback whales: Source levels increase as ambient ocean noise levels increase, The Journal of the Acoustical Society of America, 148(2), pp. 542–555. doi:10.1121/10.0001669.
Hauer-Jensen, M., 2018. Analysis of Humpback Whale Songs: Applying the traditional method – MBARI, Monterey Bay Aquarium Research Institute. Available at: https://www.mbari.org/wp-content/uploads/Hauer-Jensen.pdf (Accessed: 20 September 2023).
Kobilinsky, D., 2023. Humpback whales don’t compete with boat noise, The Wildlife Society. Available at: https://wildlife.org/humpback-whales-dont-compete-with-boat-noise/#:~:text=Researchers%20found%20that%20will%20 humpback,sounds%20have%20a%20 similar%20frequency [Accessed: 19 September 2023].
Mann, J., 2000. Cetacean societies: Field studies of dolphins and whales. Chicago, Illinois: Univ. of Chicago Press.
Marchand, A., 2022. Unraveling Mysteries of Humpback Whale Song at Olympic Coast National Marine Sanctuary, at Olympic Coast National Marine Sanctuary. Available at: https://sanctuaries.noaa.gov/news/sep22/mysteries-of-humpback-whale-song.html [Accessed: 19 September 2023].
Reidenberg, J.S., 2007. Anatomical adaptations of aquatic mammals, The Anatomical Record, 290(6), pp. 507–513. doi:10.1002/ar.20541.