We cannot imagine our lives without communication, but we are not the only animal species that use communication as a way to exchange information. In this post, we are explaining how cetacean’s communication is.
HOW DO CETACEANS COMMUNICATE?
Given that there are highly social species among cetaceans, it is essential to understand the role that communication plays in regulating social interactions in these species. When we think of communication, we usually tend to associate it with acoustic communication, and, in fact, this is the major way for cetaceans; but other types exists, such as chemical, visual or tactile communication.
ACOUSTIC COMMUNICATION: THE MOST DEVELOPED
Acoustic communication is the most important way of communication in cetaceans and the reason is that sound transmission in the water is very fast. It includes both vocal and non-vocal signaling. In some species, it can be very complex, since some of them have dialects.
Because of the fact cetaceans rely on sound, some activities such as seismic surveys may interfere in their behaviour and threaten their survival.
Non-vocal communication consists of producing sounds without using the vocal apparatus, like using flukes or flippers to strike the water surface, jaw claps, teeth gnashing or bubble emissions. By slapping their tails, cetaceans convey a threat or distress.
Breaching is the typical behaviour of most cetaceans in which they leap vigorously into the air. The originated sound may travel several kilometres and it is thought to be a spacing mechanism, to keep acoustic contact or to inform about sexual stimulation, location of food or a response to injury or irritation. It can also be a manner to remove parasites and dead skin. More studies about the purpose of breaching are needed.
VOCAL COMMUNICATION IS VERY COMPLEX IN CETACEANS
Considering vocal communication, odontocetes and mysticetes are very different. For this reason, we are explaining it separately.
Sounds of baleen whales have a social function, such as contact when in long distances, assembly calls, sexual advertisement, greeting, spacing, threat and individual identification. It is probable that they use sound as a way to synchronise biological or behavioural activities, such as feeding or breeding. You can read more about communication in baleen whales here.
Scientists agree there are three (plus one) types of sound in mysticetes:
- Low-frequency moans (1-30 seconds, 20-200Hz). These sounds can be pure tones, such as in the case of fin whales (Balaenoptera physalus), or complex sounds with harmonic structure. These sounds are used in communication at long distances. For example, 20Hz moans of humpack whales (Megaptera novaeangliae) can pass through most obstacles and travel hundreds of kilometres to reach conspecifics for signaling. It has been suggested that, without obstacles, these kind of sounds can travel from pole to pole. Amazing, isn’t it? You can hear the call of the fin whale here.
- Short thumps or knocks (< 1 second, < 200Hz). These sounds are known to be produced by right whales (Eubalaena sp), bowhead whale (Balaena mysticetus), gray whales (Eschrichtius robustus), fin whales and minke whales (Balaenoptera acutorostrata). These sounds are related to social context and activity. You can here the call of the gray whale here.
- Chirps and whistles (>1kHz, <0.1 seconds). These sounds are produced by most baleen whales.
- Humpback whale songs. You can here some songs of humpback whales here:
According to scientist, odontocete sounds can be divided into two categories:
- Pulsed sounds. All toothed cetaceans produces this type of sounds and can be used for echolocation (the production of high-frequency sound waves and reception of echoes to locate objects and investigate the surrounding environment) or communication. Echolocation in dolphins.
They can be subdivided into two types:
- Pulse or click trains (clicks). Click trains consist of sequences of acoustic pulses (50μsec, 5-150kHz) repeated over time. They are related to echolocation. Species can have a broad spectral composition, such as in the bottlenose dolphins (Tursiops truncatus), or have a narrow-band composition, as in narwhals (Monodon monoceros). In this type of pulsed sound, animals produce from 1-2 to serveral hundreds of click per second. You can hear the clicks of the bottlenose dolphin here.
- Burst-pulsed sounds (20-100kHz). These high repetition rate pulse trains; called barks, squawks, squeaks, blasts, buzzes and moans; consists of producing a pulse every less than 5μsecond, which is heard by humans as a continuous sound. They have communicative and social functions. You can hear burst-pulsed sounds in an aggressive encounter among dolphins in this video:
- Narrow-band tonal sounds (whistles) (5-85kHz). Whistles are thought to be produced only for communication purposes and not all odontocetes produce them. Because they are low frequency sounds, these sounds can travel longer distances than pulsed sounds. Some species, such as bottlenose dolphins can produce whistles and clicks at the same time, what permits to maintain communication and coordination during food search by echolocation. Even in some species, such as the bottlenose dolphins, exists signature whistles; that is a so distinctive whistle that serve to identify the animal, as if it was its name. Do you want to know more about signature whistles? Watch the video:
CHEMICAL COMMUNICATION IN CETACEANS
Chemical communication includes the smell and taste. Despite it is important in terrestrial mammals, in marine mammals it is limited.
The olfactory system in cetaceans is almost nonexistent, since there is no olfactory nerves, bulbs and tracts in adult odontocetes (cetaceans with teeth) and they are greatly reduced in adult mysticetes (baleen whales). In addition, all cetaceans close their blowholes under the water.
On the other hand, taste is more important. For example, bottlenose dolphins (Tursiops truncatus) have the ability to discriminate sour, sweet, bitter and salty solutions. However, they are least sensitive to different salt concentrations, being adaptive to the marine environment.
Other species, such as belugas (Delphinapterus leucas), release pheromones to alarm their mates and, with blood in the water, they quickly escape or become unusually excited.
Vision under water is limited by light levels, the organic matter and depth. Visual displays can be of different types, such as sexual dimorphic features, body postures and colouration patterns, which are simple; or more complex like sequences of behaviours, which indicate a context, species, age, sex or reproductive condition.
For cetaceans, visual signals are an alternative to acoustic communication when the animals are close. In the case of odontocetes, visual displays are behaviours, colouration and morphological traits.
For example, male narwhals have long spiral tusks and in males of several beaked whales there are lower teeth that protrude outside the mouth. In that cases, but they are not the only ones, these are sexually dimorphic features that may play an important role in regulating social signaling and mating.
Clear-water dolphin species show colour patterns in the body, such as spots, saddle patches, capes or longitudinal striping, such as the striped dolphin (Stenella coeruleoalba).
Finally, gestures are also important in cetaceans, such as open-jaw threat displays, aerial leaps, flared pectoral fins, tail lobs and S-shaped postures. Posture and behaviours may also inform about predators, prey or to synchronise actions among individuals in order to coordinate the group or for social interaction.
In this video, you can see a dolphin displaying the open-jaw threat behaviour.
In this one, a humpback whale is showing the tail lob display.
COMMUNICATION THROUGH TOUCH
Cetaceans may use their nose, flippers, pectoral fins, dorsal fin, flukes, abdomen and the entire body as a means of communication by touching other animals. Tactile signals are usually used together with other types. This type of communication has been noted in all cetaceans. Not only do body contact serve as a communication display, but it also may serve to remove dead skin.
For example, gray whales (Eschrichtius robustus) of San Ignacio Lagoon (Mexico) rub under small boats and tolerate petting of tourist. You can watch it here:
Atlantic spotted dolphins (Stenella frontalis), bottlenose dolphins, humpback whales and North Atlantic right whales (Eubalaena glacialis), among others, gently rub their bodies with congeneres and it is common between mothers and calves.
- Berta, A; Sumich, JL & Kovacs, KM (2006). Marine mammals. Evolutionary biology. UK: Academic Press.
- Dudzinkski, KM; Thomas, JA & Gregg, JD (2009). Communication in Marine Mammals. In Perrin, WF; Würsig, B & Thewissen, JGM (Ed.). Encyclopedia of Marine Mammals (260-269). Canada: Academic Press.
- Cover picture: Gregory “Slobirdr” Smith, Creative Commons.
Have you ever seen some of these types of communication in cetaceans? Share it with us on the comments!