I attended a display by dolphins at an aquarium in France during the summer. It was my first time seeing these creatures up close and, like the rest of the audience, I was delighted with their cleverness and sense of fun. They made lots of whistling and clicking noises. These noises could be a means of communication, but are they, in fact, a language - do dolphins speak? This question is discussed in a fascinating article by marine biologist Jim Mastro in the Nov/Dec 1999 issue of The Sciences.
It is generally accepted by linguists that only humans speak language. Of course it is clear that animals do communicate with each other, which simply means that information is transferred. We are all familiar with the aggressive bark of the dog or the odour emitted by the bitch in heat to signal sexual receptivity to the male. But language is a far richer thing.
Language is defined by several characteristics, e.g. prevarication, reference to past or future events, reference to objects not present, symbolic representation, etc. But several animal species are capable of one or more of these abilities, e.g. chimpanzees and dolphins. The dolphin is considered to be the most linguistically promising because of its large brain size and because of the range of sounds it can make.
MOST studies have been done on the Atlantic bottle-nosed dolphin Tursiops truncatus. Tursiops' brains are large and well developed. The brain to body ratio of the dolphin is the largest of any non-human mammal and is twice as great as the chimpanzee.
Dolphins have a complex echolocation system that they use in hunting. However, the large brain is not apparently necessary to support this because some bats have an equally sophisticated echo-location system but one of the smallest mammalian brains. The large dolphin brain more likely explains their complex social system. Complexity of social relations in mammals is correlated with brain size. It is proposed that human language is an evolutionary offshoot of that process.
Dolphin society may rival primate society in complexity. Dolphins frequently act co-operatively and also appear to display altruistic behaviour. Sophisticated intercommunication (perhaps language) is necessary in order to orchestrate this activity. For example, dolphin mothers frequently form swimming playpens for their calves, keeping the young safely at the centre of a circle.
Dolphins can vocalise many sounds. These have been described as "blats, bleats, chirps, clicks, creaks, pulses, quacks, racs, rasps, squeals, squawks, wails and whistles". Some of these are made for echolocation but what about the others? The most conspicuous sounds are whistles. Dolphins are good mimics and can imitate whistling sounds presented to them. If presented with two separate whistling sounds they can repeat and combine them together.
Dolphins possess signature whistles characteristic of each animal - its name if you will. But early research indicated that most of a dolphin's vocalisations are simply repeats of this signature whistle. However, this work was done using captive animals. If they speak a language, its expression might be drastically altered under captive conditions.
Recent work on dolphin whistles, studying wild dolphins, shows that the whistles are well structured and are often deliberately modified by the dolphin. Also many sounds made by dolphins fall outside the range of natural human perception and can be detected only using electronic aids.
Recent computer analysis has shown that dolphin whistles are far more complex than previously suspected. Whistles once thought to be variations of the signature whistle are now seen to be quite different. Where once it was thought that dolphins had only a few whistles, more than 100 kinds of whistle have now been detected. It may be that the dolphins can combine and recombine the whistles to convey an enormous number of messages, just as people do with words.
In some experiments dolphins have been taught that various whistles signified objects in their tank, such as a ball or a ring. The dolphins mimicked the whistles in a way that resembles language acquisition by children. They mimic the end of the whistle first, then the beginning, then put the two together. This breaking-up method suggests that the whistles may be components of a larger system.
The dolphins mimic the sound of the artificial whistle as they play and use the sounds appropriately.
Much of the work on dolphin whistles is being carried out by Brenda McCowan and Diana Reiss (University of California, and the New York Aquarium). Just imagine, if dolphins really do communicate with each other through language, and if we could learn this language, how exciting it would be. Imagine what we could learn about animal life, about language, and about ourselves if we could speak with dolphins.
(William Reville is a senior lecturer in biochemistry and director of microscopy at UCC).