One of the most interesting topics in regard to cetaceans is the way these animals manage to communicate underwater, in a world where vision and smell are made difficult by the unfavourable conditions. Whales and dolphins are considered to be some of the smartest animals on earth as they show various signs of culture, teaching their young behaviours that are essential for survival (Bender et al., 2009).
Communication is therefore a key component of these animals’ social lives and one of the proofs of their high intelligence.
The deep is, despite its quiet appearance, the realm of sounds, as they can travel in water four times faster than they do in air. As a consequence, cetaceans are extremely sensitive to sounds, having three times more neurons responsible for sound perception than humans do. They are also known to have the ability to hear up to 12 octaves, while in comparison, humans can only hear up to 8 (Ketten, 2018). But because they operate on different parts of the spectrum, not all cetaceans are able to hear each other underwater. The types of sounds produced and perceived vary with the species and they can consist of clicks, pulses, whistles, groans, cries or trills.
True whales, such as blue whales, humpback whales or minke whales, belong to the group “mysticetes” or “baleen whales”. They get this name because, for feeding, they use hair-like structures called “baleen plates” in order to filter plankton and krill out of the seawater. To communicate, these whales produce low-frequency sounds with the help of their larynx (Figure 1).
Figure 1. Baleen whale sound production mechanism. Photo retrieved from https://dosits.org/animals/sound-production/how-do-marine-mammals-produce-sounds/
Some of their vocalizations are very complex and consist of various units, organized into phrases, which in turn form different themes. When several themes are arranged into a specific order, a song is formed. One of the best-known mysticete songs is that of the humpback whale, which is possibly the longest (7-30 minutes), loudest and slowest song in nature (Payne & McVay, 1971).
Male humpback whales of all ages form aggregations in order to sing, which is thought to be a territorial display or a way of attracting females and thus playing an essential role in sexual selection. Most of the singing is performed during the breeding season, but male humpbacks have been known to sing also while feeding. Each population of humpback whales has its own unique song, with the same themes being repeated in the same order. However, these change over time, when different units or even different themes are added to them or exchanged. This way, over a few years, the same population will be singing a completely different song, which may increase the reproductive fitness of the population, like in the case of birds (Garland et al., 2011).
The following link leads to an example of a humpback whale song: https://dosits.org/galleries/audio-gallery/marine-mammals/baleen-whales/humpback-whale/
Other cetaceans such as sperm whales and all the species of dolphins feed on larger prey like fish, squid or even other marine mammals. They have teeth instead of baleen plates and therefore belong to another group called “odontocetes” or “toothed whales”. These animals use their larynx and nasal sacs to produce various types of sounds of mid- to high frequency, not only for communication purposes but also for navigation and hunting. All odontocetes are capable of biosonar or echolocation, which helps them orient themselves in the dark and also to find prey. This feature is based on the production of a series of clicks that are directed through an organ called “melon”, found in the forehead of the animal (Figure 2). The clicks then bounce off various objects or creatures and come back to the cetacean, which captures them through a fatty tissue stored in its mandible and connected to the middle ear. The vibrations are later transmitted to the animal’s nervous system, which interprets them and translates the information into a mental map of the environment, allowing the animal to have a clear view of the position of any obstacles and/or food sources.
Figure 2. Dolphin echolocation system. Photo retrieved from
Despite their essential role in navigation and hunting, clicks are not so much used for communication. For this purpose dolphins use burst pulses and whistles and it has been proved that each individual produces its own characteristic sound, called a “signature whistle”, acting almost like its name (Sayigh et al., 2007). Although these whistles lack the complexity of mysticete songs, experiments in captivity have shown that dolphins have a high understanding of both syntax and semantics and that they are capable of associating different sounds to different objects and even of mimicking human behaviour and sounds. This has inspired scientists from The Wild Dolphin Project and Georgia Tech in Atlanta to join efforts in 2010 and work with wild Atlantic spotted dolphins in the Bahamas to create a human-dolphin translating machine, called a “CHAT box” (an acronym for “Cetacean Hearing And Telemetry”), a computer that stores several coded artificial whistles assigned to various objects. The use of this machine proves that the dolphins have the ability of learning new “words” and associating them to new objects that are not naturally part of their environment and is a first step towards a better understanding of cetacean communication. You can learn more about this project on its website: CHAT Research and listen to common dolphin sounds following this link:
Given that sounds play an essential role in vital behaviours such as foraging, spatial orientation, social interactions or breeding, cetaceans find themselves to be very sensitive to loud noises. Various forms of human activity at sea such as boating, seismic surveys or military exercises are known to produce noise levels that interfere with communication and that can have harmful effects on whales and dolphins, altering both their behaviour and physiology. Humpback whales, for example, have been observed to avoid certain feeding grounds in the presence of noise sources (Risch et al., 2012), while deep divers such as different species of beaked whales have been found to mass strand when associated with military exercises (Fernandez, 2004; Frantzis, 2004). It is therefore of essential importance to continue learning about how these animals use sounds and are affected by noises in their environment, in order to be able to design and implement the best management procedures for their protection.
Written by Ramona Negulescu
Bender, C. E., Herzing, D. L., & Bjorklund, D. F. (2009). Evidence of teaching in Atlantic spotted dolphins (Stenella frontalis) by mother dolphins foraging in the presence of their calves. Animal Cognition, 12(1), 43–53.
Fernandez, A. (2004). Pathological findings in stranded beaked whales during the naval military manoeuvers near the Canary Islands. ECS Newsletter 42(Special Issue):37-40
Frantzis, A. (2004). The first mass stranding that was associated with the use of active sonar (Kyparissiakos Gulf, Greece, 1996). In P. Evans & L. Miller (Eds.), Proceedings of the Workshop on Active Sonar and Cetaceans Held at the European Cetacean Society 17th Annual Meeting, 8 March 2003 (European Cetacean Society Newsletter, 42 [Special Issue], 14-20)
Garland, E. C., Goldizen, A. W., Rekdahl, M. L., Constantine, R., Garrigue, C., Hauser, N. D., Michael Poole, M., Robbins, J., & Noad, M. J. (2011). Dynamic Horizontal Cultural Transmission of Humpback Whale Song at the Ocean Basin Scale. In Current Biology (Vol. 21, Issue 8, pp. 687–691).
Ketten, D., The University of Rhode Island (Producer) (2018) Sound reception in Marine Mammals [Video webinar] Retrieved from https://dosits.org/decision-makers/webinar-series/webinars-2018/sound-reception-mammals2018/
Photo: Dr. Joy Reidenberg. Adapted from Joy S. Reidenberg and Jeffrey T. Laitman. 2007. Discovery of a low frequency sound source in Mysticeti (baleen whales): Anatomical establishment of a vocal fold homolog. The Anatomical Record. Volume 290, Issue 6, pages 745–759. Retrieved from
Risch, D., Corkeron, P. J., Ellison, W. T., & Van Parijs, S. M. (2012). Changes in Humpback Whale Song Occurrence in Response to an Acoustic Source 200 km Away. In PLoS ONE (Vol. 7, Issue 1, p. e29741).
The Wild Dolphin Project (2010) [Website] Retrieved on the 16th of April 2020 from