How Complex is Dolphin Communication?
Dolphins language is open and hierarchically organised like ours.
The fact that bottlenose dolphins language is open and hierarchically organized means that they can produce a virtually unlimited number of signals like in human language. That means that like in human language, bottlenose dolphins can speak about any topic and describe any situation.
We only have deciphered the meaning of signature whistles. Dolphins use signature whistles in a way quite similar to our names to identify individual dolphins or groups of dolphins. Those are the only dolphins “words” that its meaning was deciphered and the simpler signals that dolphins produce.
In 1990 Alexander V. ZaninVladimir I. MarkovIrina E. Sidorova published a paper called “The Ability of Bottlenose Dolphins, Tursiops Truncatus, to Report Arbitrary Information” They have done experiments that demonstrated dolphins have a true symbolic language.
In a first experiment the dolphins were trained to push levels in response to balls of different sizes, each ball size corresponding to a specific level. In a second phase of the experiment, one dolphin received the ball an the other the level so the first must communicate the second what level to push. They succeed in 95% of trials when the system was on and 0% when it turned off. And in the 5 % that did not succeed they didn´t communicated by the system. That experiment proves that dolphins has a symbolic language.
After that Markov and Ostrovskaya studied the structure of dolphins language. They studied it recording the communications of 2 bottlenose dolphins in separated encloses connected by a system formed by a microphone and a speaker that connected them. That system worked with a sample size of 300000 hertz so it worked for frequency up to 150 Khz so it included the entire frequency range of dolphins communications.
In their next work they let the system turned on for long periods of times and recorded their communications.
Dolphin conversation from From Joshua T. Abbott, Heidi E. Harley, Jenna Clark & Wendi Fellner.
They found that dolphins language is open and hierarchically organised like ours.
That means they can combine elements in different orders to produce different meanings, they combine elements in blocks of at least 7 orders of hierarchical organization. We combine phonemes to produce words, words to produce phrases, phrases in to sentences, sentences in to paragraph, etc. that´s the hierarchical organization. Dolphins produce simple elements that are individual whistles or pulsed sounds and they combine them to form blocks of first order. They combine 1st order blocks to form 2nd order blocks, etc. Stable blocks of up to 7th order of complexity have been evidenced.
They can combine blocks of different order of complexity to produce an almost unlimited number of signals. Most of their signals are composed of 5 to 7 blocks independently of their complexity but they produce signals with 2 to 24 blocks.
They can also produce up to 4 different sound simultaneously so they can combine blocks not only by linearly ordering them like our speech but also superimposing them. Most blocks has 1 or 2 superimposed simpler blocks but they can form blocks with up to 4 simultaneously superimposed blocks. Dolphins never start 2 superimposed blocks simultaneously, The block which start first is called the base and usually is stable, the block that superimpose to it is called the superstructure and is highly variable. The base can end before the superstructure and the superstructure can become the base for a new superstructure, this is called inversion. This increase considerably the complexity of dolphin language to a grade that even our speech don´t reach.
This images shows the code developed by Vladimir I. Markov and Vera M. Ostrovskaya to describe and study dolphin language.
They published their work called “Organisation Of Communication System In Tursiops Truncatus Montagu” in a book called “Sensory Abilities of Cetaceans Laboratory and Field Evidence”, Edited by Jeanette A. Thomas and Ronald Kastelein (Harderwijck Dolfinarium) NATO ASI Series A : Life sciences Vol.196
The paper of Zanin, Markov and Sidorova is in that book too.
Markov and Ostrovskaya, Using this data and standard formulas from Games Theory, calculated that 10 exp. 12 signals could be produced by means of free combining.
This is a potential estimate, but even if we assume that, because of code-associated or physical block combination bans, only one ten millionth of them actually is used, still there remain 100000 signals available for communication which certainly is more than required for actual communication.
All this makes it possible to think that the communicative system of bottlenose dolphins is “open” in terms of vocabulary formation.
This conclusion is indirectly supported by the fact that dolphins use hundreds of structural types of signals for communication.
It is rare that bottlenose dolphins produce single signals. As a rule, this is typical of very young or isolated adult animals.
In normal communication, the intensity of signalization is very high, reaching sometimes 50 signals per minute (remember that each signal is composed of 5 to 7 blocks independently of their complexity but they produce signals with 2 to 24 blocks).
In free dialogue (for instance, during communication of isolated animals through electroacoustic communication link), signals with different structures are combined into groups, the way human words are combined to construct phrases.
Grouping is well-pronounced in normal conditions of communication between calm animals but it drastically changes or disappears in stressed situations, when the frequency range of communication is severely restricted or communication between individuals is broken.
In a number of situations, when dolphins mostly are using tonal signals, one can identify sets of tonal signals with a common structure component.
The analyses of variability of signals from the set, has shown that their middle sections are most stable, while edge sections (especially those at the end) are extremely variable.
Variability behaves differently in groups composed of different signals. This allows one to assume that the order in which signals follow each other in groups, is meaningful for the dolphins and that the described variability depends on the interaction of signals and, consequently, on the existence of organization in a sequence of signals.
This assumption is supported indirectly by dolphins producing groups with identical composition, sometimes consisting of signals with very complicated structure.
This assumption is rather non-trivial and actually recognizes the ability of bottlenose dolphins to generate organized messages (text).
Complex dolphin signal that includes complex superimposed blocks of whistles and pulsed sounds From Joshua T. Abbott, Heidi E. Harley, Jenna Clark & Wendi Fellner.
Dolphins use signature whistles in a way quite similar to our names to identify individual dolphins or groups of dolphins. Those are the only dolphins “words” that its meaning was deciphered and the simpler signals that they produce as they are in the level of simple elements (they don´t reach the complexity of even 1st level blocks).
Signature whistle spectrogram From Joshua T. Abbott, Heidi E. Harley, Jenna Clark & Wendi Fellner.
Male bottlenose dolphins use own ‘names,’ study finds | DW | 08.06.2018
We only have deciphered the meaning of signature whistles but those are only the simpler signals dolphins produce, signature whistles don’t reach the complexity of 1st order blocks they are basic elements. Dolphin signals have the capacity to encode at least 6 times more information than human language. Some authors suggest that dolphin language encodes up to 100 times more information in the same time.
Dolphin language also has a complex grammatical and complies with zip´s law.
In 2009 Abbott used statistical language processing to analyze structure in sequences of vocalizations produced by Atlantic bottlenose dolphins and he found that that sequences of dolphin vocalizations are constructed in a non-random fashion, i.e., they follow syntactic rules.
He found bottlenose dolphins signals are composed by are well-defined sets of vocalizations which begin and end sequences, and correlation between successive vocalizations is very strong. Overall, these findings establish compelling evidence that there is significant structure in sequences of dolphin vocalizations, i.e., a syntax.
The same analysis to the non decoded hieroglyphic signals of a civilization now known as the Indus with similar results.
In 2016 Vyacheslav A.Ryabov recorded communications between 2 bottlenose dolphins using a two-channel system in the frequency band up to 220 kHz and found that their language exhibits all the design features present in the human spoken language, this indicates a high level of intelligence and consciousness in dolphins, and their language can be ostensibly considered a highly developed spoken language, akin to the human language.
https://ac.els-cdn.com/S24057223...
The fact that bottlenose dolphins language is open and hierarchically organized means that they can produce a virtually unlimited number of signals like in human language. That means that like in human language, bottlenose dolphins can speak about any topic and describe any situation.
Dolphins produce 2 kinds of sounds that they combine to produce blocks. Tonal sounds or whistles and pulsed sounds. Tonal sounds are transmitted equally in all directions like most sound. Pulsed sounds are highly directional.
Echolocation sounds are very short clicks with a duration of 8–72 μs and a frequency range from 40 to 140 KHz. They are usually produced with a time interval that corresponds to the time sound need to travel from the dolphin to the target and back again when the target is close. When the target is hundreds of meters far away they produce a lot of clicks in trains and then they wait that all the reflexes come back.
Dolphins adjust the frequency of the clicks depending of the distance of the target (lower frequency travels further and higher frequency for a more detailed image) and depending on the properties of the target (higher frequency to see the details of the surface of the target and lower frequency to see through it).
Echolocation click train spectrogram From Joshua T. Abbott, Heidi E. Harley,
Jenna Clark & Wendi Fellner. Clark & Wendi Fellner.
Communication sounds can be tonal or pulsed. The signals that dolphins produce generally is a complex combination of both.
Dolphins produce different kinds of whistles. Low frequency whistles 15–25 KHz are simple and are used to communicate in large distances (various Km). One kind of whistles of this type are signature whistles that are used to identify themselves like our names. They also use higher frequency more complex whistles as part of more complex signals usually combined with pulsed sounds.
Pulsed sounds can be clicks, clicks trains, narrow-band burst pulses, or broad-band pulses. Communication clicks are longer than echolocation clicks (0,1–3 ms) and with a more complex frequency content.
Communication sounds can be tonal or pulsed. The signals that dolphins produce generally is a complex combination of both.
Dolphins produce different kinds of whistles. Low frequency whistles 15–25 KHz are simple and are used to communicate in large distances (various Km). One kind of whistles of this type are signature whistles that are used to identify themselves like our names. They also use higher frequency more complex whistles as part of more complex signals usually combined with pulsed sounds.
Pulsed sounds can be clicks, clicks trains, narrow-band burst pulses, or broad-band pulses. Communication clicks are longer than echolocation clicks (0,1–3 ms) and with a more complex frequency content.
Communication clicks. from Vyacheslav A. Ryabov The study of acoustic signals and the supposed spoken language of the dolphins.
Communication clicks. from Pulsed signal properties of free-ranging bottlenose dolphins (Tursiops truncatus) in the central Mediterranean Sea.
Pulses are aggregate groups of clicks with very short intervals. They are high-frequency pulses, 4–9 ms long. They are characterized by a triangular shape of the amplitude envelope. They can produce narrow-band burst pulses that changes frequency forming a complex contour.
By means of “primary grouping”, pulses of the same type and with identical spectra can be organised in time in a certain way:
- single pulses are combined in groups containing 2–10 pulses;
- these groups, as well as single pulses, can be used to form train-sequences with different pulses density.
Though individual pulses and groups can be used occasionally as independent signals, it is trains which play the major role in pulsed signalization of bottlenose dolphins.
During sound generation, bottlenose dolphins can, either successively or simultaneously, change the
density in a train, the grouping of constituent pulses or their spectrum, and such changes can be very fast.
As a result, the ultimate structure of the signal will consist of different fragments connected by transformation zones, which result from successive combining of blocks with stable temporal and spectral characteristics.
Burst-pulse and whistle combination From Joshua T. Abbott, Heidi E. Harley, Jenna Clark & Wendi Fellner.
Tonal sounds are transmitted equally in all directions like most sound. Pulsed sounds are highly directional so some researchers think they can shape them to form images. If this is confirmed, dolphins language would be even much more versatile and complex than we can imagine.
There is evidence that dolphins can eavesdrop others dolphins echolocation signals so they probably can produce 3 dimensional sound images using pulsed sounds. We don’t know how detailed are those images, they can be as detailed as the echolocation images but they may be like drawings or symbols and some dolphins may be better at drawing with sounds than others
Pulsed sound imaged probably enriches a lot dolphin language but it is not necessary to proper communication at least in bottlenose dolphins. In other words Bottlenose dolphins can report arbitrary information without them as Zanin, Markov and Sidorova demonstrated in their research since the phone like system they used to communicate dolphins did not transmit the spacial shape of their pulsed sounds. Nevertheless they were aware of the importance of the shape of pulsed sounds since they started to work on a system to record and reproduce the spacial shape of pulsed sounds. Regrettably their project was discontinued dew to lack of funds as a consequence of the fall of the Soviet union. Today there are some researchers who are starting to study the spacial shape of dolphins pulsed sounds but they work is very preliminary.
Nevertheless we now know that some species of dolphins, such as the Hector dolphin (Cephalorhynchus hectori), the Commerson dolphin (Cephalorhynchus commersonii) and the heaviside dolphin (Cephalorhynchus heavisidii), communicates using high frequency spatially complex shaped pulsed sounds that are organized relatively simply in time.. These dolphins do not seem to have a complex organisation such as the bottlenose dolphin and their communication system is mainly based on images with pulsed sounds. This dolphin species rarely use whistles for communication.
Signature whistles have been studied in many dolphin species. Their world wide variation have been studied at least in bottlenose and spinner dolphins. In bottlenose dolphins signature whistles from stable populations have a lot of characteristics in common but are very different than signature whistles of bottlenose dolphins of a different population so some researchers can recognize where is a bottlenose dolphin from with his signature whistle. they entire language may be different between populations.
Differences in the whistle characteristics and repertoire of Bottlenose and Spinner Dolphins
Bottlenose dolphins has a language that is more complex than ours. With signals that are sentences composed by superimposed very complex blocks of information enriched by projected sound images they can transmit a lot of detailed information in very short times. Usually bottlenose dolphins interchange signals that has an average duration of 2 seconds but are composed by 5–7 blocks (of up to 7th level of complexity) in average but can have more than 24 blocks so they can transmit 6 to 100 time more information than us in the same amount of time.
They probably describe them in a way much more complex that we can do or even imagine. This is possible because dolphins has a sound production system much better than ours that allow them to develop languages that are much more complex than ours even with cognitive abilities similar to ours.
In the same way that our hands an fine motor skills allow us to make tools and constructions and manipulate our environment in ways their cannot even imagine even with cognitive abilities similar to us.
Orcas
Orcas have some demonstrated sentences comprehension abilities. In captivity it has been demonstrated they can understand a series of orders in tandem like do a, then b, then c, etc. but it has not been demonstrated that they can understand complex sentences but this do not mean that they cannot we only lack the evidence. For chimpanzee, bonobo, gorilla and orangutan there is evidence that they cannot understand complex sentences.
Orca vocalizations has a lower frequency than bottlenose dolphins vocalizations so they are mostly audible and easier to study. Unlike bottlenose dolphins, most sounds produced by killer whales are within the range of human hearing.
Like other dolphins orca uses tonal sounds and pulsed sounds.
When they forage they use stereotyped pulsed calls to coordinate their movements. Each pod has a set of pulsed calls they use to communicate when they forage. They can combine those pulsed calls in different orders to produce complex signals. Each pod has a repertory of around 9 to 16 pulsed calls.
When orcas socialize they use tonal calls. Each pods produces specific tonal calls and they repeat them several times. They respite them in a similar way but not always the same. In other words they repeat the calls with some variation. Each pod have a small number of calls that identifies them. they use them to identify themselves as a pod (not for individual identification). Related pods have similar calls with stable differences and unrelated pods have calls that are more distinct, so we can talk about different dialects and languages.
When some related pods reunite themselves in bigger pods they use a special set of calls called biphonic calls that are composed by 2 superimposed calls. Biphonic calls has similarities with normal calls and they are only used when different related pods reunites together to mate.
Spectrograms of a a monophonic vocalization and b a biphonic vocalization. From Usage of monophonic and biphonic calls by free-ranging resident killer whales (Orcinus orca) in Kamchatka, Russian Far East. O. A. Filatova I. D. Fedutin M. M. Nagaylik A. M.Burdin E. Hoyt.
Orcas do not communicate with other orcas that uses different calls only with orcas that uses very similar calls.
The tonal calls that orcas produce when socialize are repetitions of the same very few calls with some variations without changing the principal characteristics of the calls. So it seems they have more in common with our music (with rhythm and melody) than with a true language.
In the other hand pulsed calls seems to be a symbolic language and they seem to has some hierarchical organization but not at the level of bottlenose dolphins blocks. They also are a small set of stereotyped signals so orca language seems to be symbolic and with some hierarchical organization but it not seems to be an open language. That means that unlike bottlenose dolphins an humans they can produce a limited number of signals and this limits the information they can transmit to limited topics. Probably this language allows them to plan and coordinate foraging but not to talk about anything else. So they only use this language when they hunt and when they socialize they use music like tonal calls.
Unlike bottlenose dolphins, orca communication has no grammatical structure.
On the communicative significance of whistles in wild killer whales ( Orcinus orca)
Orcas do not uses signature whistles but they have been observed trying to imitate bottlenose dolphins signature whistles but they did not used to call them or identify them (that do not mean that they don`t understand them).
Dolphins in general
Bottlenose dolphins and orcas are the most studied dolphins but there are lot of dolphins species with great variability.
Most delphinids use tonal and pulsed sound for communication. Bottlenose dolphins use combinations of complex blocks that include both tonal and pulsed sounds, and their simpler signals are the signature whistle a tonal sound. Other dolphins species like Atlantic spotted dolphins (Stenella frontalis) and indopacific bottlenose dolphins (tursiops aduncus) appear to use a similar structured language. Probably other related species have a similar structured language too.
Orcas use pulsed sounds to coordinate foraging ant tonal sounds for socialize. Other species like pilot whales (globicephala sp.) has a similar language but they include some pulsed sounds in their socializing tonal songs. It is not known what this means but I think it may be something similar to when we sing including words in a melody. False orcas (pseudorca crassidens) take this to a more complex level creating very complex sounds including tonal and pulsed sounds.
Other dolphin species like dusky dolphins (lagenorhynchus obscurus) and pacific white sided dolphins (lagenorhynchus obliquidens) use mainly high frequency pulsed sounds for communication with very few whistles.
Some species of dolphins like hector´s dolphin (cephalorhynchus hectori); and probably the rest of cephalorhynchus genera, and the hourglass dolphin (Lagenorhynchus cruciger) don´t use tonal sounds (whistles) at all they only use pulsed sounds of very high frequency of over than 100 KHz. This frequencies are over the hearing range of orcas their main predator. This dolphins uses different kinds of clicks for echolocation and for communication. Their communication is similar to porpoises communication with narrow-band high-frequency click trains that are very stereotyped but more complex with some burst pulses with different frequency content some as low as 50 KHz.
Nevertheless we now know that the Hector dolphin (Cephalorhynchus hectori), the Commerson dolphin (Cephalorhynchus commersonii) and the heaviside dolphin (Cephalorhynchus heavisidii), communicates using high frequency spatially complex shaped pulsed sounds that are organized relatively simply in time.. These dolphins do not seem to have a complex organisation such as the bottlenose dolphin and their communication system is mainly based on images with pulsed sounds. This dolphin species rarely use whistles for communication.
Sperm whales
Sperm whales communicate between themselves with codas. A coda is a stereotyped click train with specific temporal and frequency pattern. Each pod of sperm whales has a bounded and stable repertoire of codas different to other pods. They use them when they socialize like orcas with their tonal signals. Related pods have similar codas with small differences and unrelated pods has very different codas. When they hunt they tend to do it alone with echolocation clicks and sometimes sound pulses but they only use codas when socializing.
Porpoises
Harbour porpoises communicate with narrow-band high-frequency clicks. They likely mediate social interactions, such as mate choice and mother-calf contact, with sound. That narrow-band high-frequency clicks have repetition rates and output levels different from those of foraging click trains.
hese sounds are produced in bouts and frequently that co-occur with emission of similar sounds by nearby conspecifics. This narrow-band high-frequency click trains are consistent with a communication function. Nevertheless this narrow-band high-frequency click trains are very stereotyped and not as complex and versatile as the whistles clicks and burst pulses produced by delphinids. So Even if they are well suited for communication they are not complex enough to be a open and hierarchically organised language like those of dolphins and humans.
Vaquita communications are not well studied but some recordings have been done and their communications seems to be very similar to harbour porpoises communications which have been studied.
River dolphins
River dolphins are not delphinids, they are more closely related with beaked whales than with oceanic dolphins. Their brains are 1/2 to 1/3 the size of oceanic dolphins brains of the same size. Bottlenose dolphins has a brain size 3 times or more than amazon river dolphins of the same size.
River dolphins don´t use whistles they produce 2 kinds of clicks one for echolocation and other for communication both with frequency over 100 Khz like porpoises and cephalorhynchus delphinids.
Misticete whales
Misticete whales sing specially to attract females. Only males sing.
Songs in whales are learned by listening other whales sing. Each whale introduces variations to the song and when a whale son become very effective to attract females others copy that song so this song becomes trending in that whale population. With time this song can spread to other populations and become trending in all the hemisphere.
Although songs change gradually each year, humpback whales population also completely replaces their song every few years in cultural ‘revolutions’. Revolutions involve learning large amounts of novel material introduced from other whales populations. Songs complexity increases as songs evolved over time but decreases when revolutions occur.
Rise in complexity may represent embellishment to the song which could allow males to stand out amidst population-wide conformity. The consistent reduction in complexity during song revolutions suggests a potential limit to the social learning capacity of novel material in humpback whales.
Bottlenose dolphins seems to have a more complex language than other species of cetaceans but we need more research to know this for sure.
