THE LANGUAGE OF CETACEOUS
In the kingdom of the seas and oceans, sound is essential to the survival of the beings which populate it. Below 50 meters in depth, it becomes more and more dark until there is total obscurity.
We are entering the world of bioluminescence and acoustics. The understanding of the marine environment induces for humans, a « mental adaptability », giving up our human references to integrate another paradigm. This universe brings specific skills to its inhabitants so that they can be born, grow, evolve and perpetuate the species.
WHALES AND DOLPHINS SENSES
Living under water creates a lot of challenges for a mammal. The senses of whales and dolphins have had to adapt to this environment where sounds, light and smells do not flow as in the air.
Cetaceans have good vision in the depths. Their photoreceptors are particularly receptive to the bluish light, the light that penetrates most deeply into the water. Unlike us, cetaceans have good underwater vision both near and far. They also have a good vision in the air, as we know their ability to reach objects (like dolphins in captivity). Some mammals such as humpback whales are very curious and watch their aerial environment for a long time, their heads out of the water.
SMELL AND TASTE
Olfactory messages flow slowly in the water. The sense of smell seem to be absent in cetaceans, but they taste what they eat.
JUST A SMALL TEXT ON …. TALKATIVE FISHES !
Cetaceans are not the only ones to make sounds. It is interesting to know that the sound emission is a communication mode found in more than 50 fish families including the clown fish (the famous Nemo for children!). This fish uses sound to identify other species, size, sex, to repel intruders or to strengthen couples’ coherence when breeding.
The sense of touch is particularly developed at head level, near the vent. They can detect the surface of the water and open their vent to breathe. Touching is important in cetaceans, whales touch their fins, caress each other. Beluga females and humpback whales often swim while maintaining physical contact with their young. Baleen whales and freshwater dolphins have vibrissae (kind of whiskers) at the end of the snout to test the plankton density or detect prey in the mud.
Emitting and receiving sounds allows it to locate itself geographically, to move, to feed itself, to breed, to warn of danger, to gather together, to learn, to play …
The cetaceans can receive sounds in different ways : ear, lower jaw and surface of the body. They do not have an outer ear, but the ear system is similar to other mammals, with some functional evolutions.
A wax plug closes the tiny auditory orifice placed behind the eye.
A SIXTH SENSE …
Several studies tend to show that cetaceans can perceive variations in the earth’s magnetic field. This sense would allow them to orientate themselves in the North-South axis of the earth and would help them in their migrations.
THE PRINCIPLE OF ECHOLOCATION :
Echolocation is a directional ultrasound emission. The toothed whales have that ability to emit ultrasound, locate themselves geographically and locate their preys. Baleen whales do not have this ability. Echolocation involves high-powered sound emission and weakened sound reception, which requires a very sensitive hearing device.
During their fifty minutes dive sperm whales transmit a long series of clicks at a steady pace. Those echolocation clicks are used as a sonar to locate the seabed and prey.
The sound emissions of dolphins (odontocetes) are produced by air circulation in their upper respiratory system, between two bladders, by resonance, or through the diaphragm. The air passes through an anatomical structure located in the head called « phonic lips » or « monkey snout » comparable to human nasal passages.
When the air goes through this narrow passage, it causes, like human snoring, suction and joining the phonic lips and the vibration of the surrounding tissues with emission of sounds.
Unlike man, there is no escape of air to produce sound because of necessary apnoea. However, baby dolphins who do not yet know how to « talk », let air pass through their vent when they whistle.
Whales (mysticetes) do not need a « monkey muzzle » type structure. They do not have vocal cords, but their larynx seems to play a role in sound emission. However, it is likely that they also use closed circuit air. Their cranial sinuses have been used to produce sounds but the process is not yet known.
Small precision: designation of whales and dolphins come from everyday language. The scientific precision distinguishes toothed whales: odontocetes (dolphins, orcas, sperm whales, belugas …) and baleen whales (humpback whale, blue whale, fin whale …)
TYPES OF SOUND EMISSIONS:
A wide variety of sounds is produced and differs according to marine mammals. We can hear: hissing, crackling, squeaks, screams, grinding, clicks, squeals, meows … This wide variety of sounds belong to different widespread classes: impulses, whistles, mixed and complex sounds.
The reception of sound is done in several ways by cetaceans: the ear, the lower jaw and the surface of the body. Cetaceans do not have an outer ear, but the inner ear/middle ear system is similar to that of other mammals. The auditory orifice of the whales and dolphins is tiny and is located behind the eye. It is closed by a waxy stopper.
In diving, cetaceans are able to know the origin of a sound. Internal hearing organs are situated in a tympanic bone, which is isolated from the bones of the skull by a cushion of greasy thickness saturated with microbubbles of air.
This air cushion shields the sounds transmitted by the skull bones and reflects them. Thus their ears are isolated from each other and the sounds picked up by the auditory canals will be perceived with the necessary shift to the brain to locate the origin.
A tympanic whale bubble (mysticete) designed to isolate the inner ear in order to preserve the sonic depth.
UNDER WATER, A SOUND PERCEPTION DIFFERENT FROM HUMANS :
In humans, the inner ears are not isolated from skull bones. Under water, the reception offset is too short to be perceived by our brain because when we are immersed, our ear canals fill with water up to the eardrums.
Our body does not react to sound like in the open air but it absorbs and transmits it directly to the inner ear through tissues and cranial bones.
Deprived of any sonic depth, we are unable to locate the source of emission.
ROLE OF CETACEOUS SOUND PRODUCTION :
The sound emissions of cetaceans allow them to communicate with each other.
They have a key role in the education of their juveniles, social cohesion, warning of danger, identity recognition between two groups. Games with dolphin also give rise to sounds.
In whales, we talk about the song of whales.
Humpback whales (Megaptera novaeangliae) feed on plankton in cold waters
and then migrate to the warmer waters to mate or give birth to their young.
To welcome the babies and prepare the territory, the males sing for three weeks. This song, composed of several sequences, varies each year and is specific to each group. It is very strange to note that all the humpback whales in the world have a common song, renewed every year. Note that the tribes do not meet because they migrate only in the direction north/south and south/north. It is therefore assumed that a form of telepathy can be used to transmit information and communicate over great distances.
Most mysticetes express themselves in very low frequency or infrasound. These sound waves propaget over long distances. An American bio-acoustician has captured sound of a cetacean at a very low frequency at a distance of 3 500 kilometers. The right whale and the megaptera have the distinction of making sophisticated broadband sounds.
In general, the frequency band of cetacean emissions is between 10 and 150 kHz. The human ear perceives only the lower spectrum part below 18 kHz and above 20 Hz.
The most « noisy » cetaceans are odontocetes: dolphins, sperm whales.
BUT WHAT DO THEY SAY?
In the current state of scientific knowledge, we are not able to understand the discussions between dolphins or whales and the meaning of what they often try to tell us. Many experiments have tried in vain to learn a language with dolphins and on the other hand, no research protocol has allowed us to decode the « dolphin ». Language.
Neurobiologists like John Lilly have recorded human words reproduced by the dolphins, imitations of laughter, the diffusion of a beluga’s vocalisations surprised the public because the sounds were very close to the human voice with similar harmonics. The bigger picture is made up of smaller ones and personal experiences that often break empirical conceptions and limiting principles. It is through passion, curiosity and respect that the understanding of beings so close and yet so different is emerging.