Dolphins have the ability to communicate with each other, and for that purpose, they use sounds and body movements. Scientists have been very interested in the way they produce sounds, and the studies they have carried out show that dolphins are animals with a diversity of sounds and a complex language.

Sound waves travel nearly 4.5 times faster in the aquatic environment than in the air. The sounds are essential in the life of any dolphin and in general, of any cetacean. Dolphins communicate, hunt, avoid predators and orient themselves when navigating through sound emissions in the water, therefore, they are very sensitive animals to noises emitted in and out of the water.

Not all sounds are the same. They vary in frequency, volume, wavelength and pattern and depend on the intention or the situation in which the dolphins are. If they are scared, excited or in a context of socialization, they tend to make whistles, but if they are in trouble, they make clicks with their jaws. In general, they communicate using low-frequency sounds but emit other high-frequency signals when using echolocation.

Most people have heard the chirping, squeaking noises made by dolphins which they use to communicate with other dolphins or for echolocation. Dolphins can use echolocation to detect even a three-inch object as far as the length of a football field.

Sounds are essential in the life of any dolphin and in general, of any cetacean.

TYPES OF SOUNDS

Within the range of sounds that dolphins produce are whistles, squeaks, crunches, clicks and some similar to screams. From a general perspective, the sounds can be burst-pulsed or frequency modulated. Sometimes a separation of a burst of clicks to the previous ones is made when used for echolocation and not precisely for communication between the members of a pod.

Dolphins produce frequency modulated sounds by changing the tone while emitting them, that is, it can go up or down. Pure whistles, squeaks, and squeals are frequency modulated sound. Bottlenose dolphins have a “signature whistle,” well differentiated from other sounds, which identifies a particular dolphin from the others.

On the contrary, the burst-pulsed sounds are brief, emitted successively and at regular intervals. In this category are clicks and bursts produced when the cetacean emits clicks remarkably fast.

DOLPHIN COMMUNICATION PROCESS

Dolphins produce sounds from the vibrations of an air sac in their respiratory cavities. They lack vocal cords, so they are unable to make emissions with them.

Production and emission.
When the air enters through the blowhole the nasal air sacs swell and Some structures of the nasal passages, called phonic lips, open and close continuously, making vibrate the surrounding tissues, generating sound waves.

The waves group in bundles in the melon and the dolphin directs them forward. Then the sound waves bounce back when they find objects in their path.

Reception.
Part of the signal bounces back and returns to the dolphin as an echo. It may seem strange, but the bones of the lower jaw are the principal areas of reception of sounds. From there they travel to the inner ear and then to the auditory centers of the brain.

Interpretation.
The brain receives the returned sound waves in the form of nerve impulses, and the dolphin can interpret the echo.

One of the primary uses of sounds by dolphins is for echolocation, which is an ability of Odontoceti cetaceans, based on the emission of sounds and the interpretation of their echo.

DO DOLPHINS HAVE LANGUAGE?

Whether or not dolphins have language is a matter for debate unless and until we humans figure out how to speak to them. But evidence is mounting that dolphins may indeed have a language.

There is a lot of research on dolphin vocabulary that indicates they communicate with at least as much sophistication as the higher apes. They have a lexicon of danger sounds, food sounds, seeking sounds, and sometimes they put these sounds together in a reasonably sophisticated fashion. There is evidence that they may greet one another by name because they utter unique sounds when meeting other dolphins.

DOLPHINS AND MAN-MADE SONAR

Dolphins are incredibly good at distinguishing their echolocation sounds even in very noisy underwater environments. It has also been found, though, that some noisy locations confuse dolphins.

Beaching is probably the most tragic thing that we can see: a pod of dolphins that have apparently killed themselves by swimming onto a beach and lodging themselves there.

Why do dolphins do this? The most accepted theory is that something confuses their echolocation, taking them to the beach instead of the open ocean. Some autopsies of beached dolphin bodies show a very high percentage of damaged hearing, suggesting that a powerful sound may have blown out their hearing.

Although dolphins see quite well, without their hearing sense, they are disoriented and blinded. And when one dolphin beaches itself, the others are at risk because they will try to help it.

References

https://dolphins.org/acoustics

http://biol.wwu.edu/mbel/media/pdfs/AquatMamm2004_30.pdf

https://www.uaeh.edu.mx/scige/boletin/prepa3/n1/r2.html

Janik, Vincent; Laela Sayigh (7 May 2013). “Communication in bottlenose dolphins: 50 years of signature whistle research”. Journal of Comparative Physiology.

Dolphin Mysteries: Unlocking the Secrets of Communication. Yale University Press. 2008.

Denise L. Herzing. Dolphin Communication and Cognition: Past, Present, and Future. MIT Press, 2015.

Communication, strictly meaning, involves the transmission and feedback of coded messages. However, the complexity of the communication processes seems to be exclusive to the human race.

Despite this, it is clear that dolphins have a sophisticated communication system which is the reason for their success against their predators. In short, dolphins survive because they communicate with each other and this allows them to organize and cooperate to increase their probabilities of survival.

HOW DO DOLPHINS COMMUNICATE?

Dolphins communicate through the emission and reception of sounds; Each dolphin develops its distinctive sound since the first years of life. All individuals produce a unique sound, which is different to the others so they can fully identify each other.

Dolphins emit two types of vocal sounds: continuous tone and burst-pulsed sounds.

But, how do they produce these sounds? While dolphins are devoid of vocal cords, they emit sounds through their larynx, in the region of the nasal air sacs. These sounds do not mean that dolphins have a voice, but there is a tissue in the nasal area that has structures that project in the duct. When the air passes through that section, the tissue vibrates, and so the sound is produced.

Dolphins emit two types of vocal sounds: continuous tone and burst-pulsed sounds. The first type includes whistles, squeaks and some species of squeals. They are “frequency modulated sounds” because dolphins modify the tone of the sound, this is, it can rise and fall over time. The burst-pulsed sounds are recognized by the superposition of sound waves and refer to the “clicks,” produced successively at regular intervals.

WHERE, WHEN, WHAT

Different emissions, different context. Dolphins can make sounds to interact socially: when they separate from their peers, when they are excited, when alarmed or just when they feel happy. The sound depends on the situation. Lost dolphins have been observed to produce whistles frantically in an attempt to call their companions, and individuals of some species emit pulsating sounds if they become excited or angry; Apparently, this is intended to make known their emotional state to other dolphins.

Sometimes bottlenose dolphins (Tursiops truncatus) produce a blast that invites other individuals to play, as a way of informing them that they are in a good mood and want to have fun with them. Very high pulsating sounds are used during aggressive encounters to call other dolphins, and others direct to the genital area of ​​females when males chase them and flee. Mothers often whistle their offspring for several days after birth.

Bottlenose dolphins distinguish different frequencies depending on what they want to communicate. Low-frequency sounds (0.25-50 kilohertz) are used to communicate in social situations while high frequencies serve in echolocation. Another case: during the aggressive persecutions of Indo-Pacific dolphins (Tursiops aduncus), they issue a kind of crunch that is called “pop” sound.

The human ear perceives successive clicks as a sound without interruption, but the truth is that they are short. We do not know much about the purpose of the different sound emissions and researchers are still working on sound-target identification.

SIGNALS WITHOUT “VOICE.”

Although dolphins rely primarily on sounds to exchange information, they also communicate through touch and body language:

Identification of body coloring patterns.
Stains, stripes, and specks may indicate to other dolphins the health status or the age of their companions. For example, the skin of the Atlantic spotted dolphin (Stenella frontalis) develops spots when it begins to get old, and the scars in the skin of the Risso dolphin (Grampus griseus) informs others of their combat skills and experience.

Postures.
The body positions convey the idea of ​​the dolphin’s mood. An S-shaped posture demonstrates anger or aggression and is a way of saying “do not mess with me now.” If they are in a fight, they can expand their pectoral fins and extend their jaws to look bigger and more dangerous.

Touch.
The skin of these cetaceans is very sensitive to the touch. If they are in a good mood, then they can make physical contact with the flippers by pressing them against the flippers of another dolphin.

Tail Slapping.
It is a vertical blow of the tail against the water surface that often indicates aggressiveness, but it can also express the desire to leave the area where they are or ask for attention.

Flipper Slapping.
It probably has the same goals as the blows on the surface with the tail, but in this case, Dolphins hit their flippers against their body or the water surface.

DOLPHIN LANGUAGE AND COMMUNICATION

Dolphins are almost constantly making one of two kinds of sounds: communicative or navigational. They produce these different sounds in a variety of ways.

Echolocation sounds are produced in their nasal passages just below their blowholes and are called clicks. Dolphins create these clicks sometimes in such rapid succession that they sound like buzzes or even quacks. These sounds are produced just behind the melon, an oily, slightly off-center lump on what you’d call the dolphin’s forehead, and the sound waves are focused forward through this organ.

Scientists are not entirely certain how the melon works, but it does seem to amplify, clarify and direct the dolphin’s echolocation sounds which allow dolphins to detect remarkably detailed information from the world around them. In one test, a dolphin found a marble-sized sphere at more than the length of a football field. Some scientists speculate that echolocation sounds may also be used to deliver an acoustic shock to small prey.

In the larynx, dolphins can produce high-pitched whistles and squeals which can rapidly change pitch. Whistles are single tones, with no vibrations that make them sound like buzzes. As far as scientists can tell, the whistles are a form of communication with other dolphins, and squeals are used to express alarm or sexual excitement.

DOLPHIN COMMUNICATION

Like some other animals, dolphins do have communication. But do they communicate linguistically? There’s some evidence for it. Dolphins tend to stay within their pods and may have trouble understanding “foreign” dolphins. In studies done on dolphins near Scotland, individuals appear to have names; or at least, other dolphins use specific and unique whistles only in the presence of certain other dolphins, as if calling them by name. Unlike any other animal besides humans, dolphins exhibit a tendency to take turns when vocalizing – making their communications sound like a conversation.

There have also been very basic linguistic studies of dolphin sound patterns. According to some studies, dolphin sounds follow the same basic patterns of all human-based language, from Morse code to Chinese.

References

https://dolphins.org/communication

Denise L. Herzing. Dolphin Communication and Cognition: Past, Present, and Future. MIT Press, 2015.

Thomas I. White. In Defense of Dolphins: The New Moral Frontier. John Wiley & Sons, 2007.

Roitblat, Herman, Nachtigall. Language and Communication: Comparative Perspectives. Psychology Press, 2013.

http://www.bbc.com/news/science-environment-23410137

https://seaworld.org/en/animal-info/animal-infobooks/bottlenose-dolphins/communication-and-echolocation

Adult bottlenose dolphins have a length ranging from 10 to 14 feet long and weight 330 to 440 pounds. The body length and weight vary according to the region where they live and the quality and availability of food. There are specimens up to 1,100 pounds, but they are not common.

Dolphins do not have external ears, but they can hear through a sophisticated hearing sense located in two small openings on both sides of the head.

However, scientists believe that dolphins hear underwater through the lower jaw bone which conducts sounds to the middle ear.

Dolphins can listen to a broader range of frequencies than humans.

While we can hear sounds from 20 Hz to 20 kHz, dolphins can hear from 20 to 150 kHz being up to 7 times more sensitive their hearing sense than the human ear.

Therefore we are not able to listen to a significant number of sounds made by dolphins.

Dolphins communicate through a group of several specialized sounds and whistles. There are several kinds of them used by these cetaceans.

Some species of dolphins can send identity information through signature whistles.

Whistles also coordinate group hunting which makes feeding much easier and efficient for dolphins than doing it alone.

Burst-pulsed sounds are also made by dolphins with the purpose of communication, although there is not enough knowledge about dolphin communication.