Animal Communication

16Ch16_OGrady.QXD 1/8/08 3:27 AM Page 514 CHAPTER Sixteen Michael Dobrovolsky Animal communication As I listened from a beach-chair in the shade To all the noises that my garden made, It seemed to me only proper that words Should be withheld from vegetables and birds. W.H. AUDEN ommunication—the passing on or exchange of information—distinguishes what is living Cfrom what is non-living in nature.1 Communication is found even in the apparently passive world of plants; trees, for example, have been found to pass on information about advancing predators by means of chemical signals. Animals communicate among them- selves and with humans so effectively that they are often said to use ‘language’. But the words communication and (human) language do not mean the same thing. Human language is a specific way of communicating, but not just any form of communication qualifies as language. A question that therefore interests many linguists is whether animals make use of any system of communication that genuinely resembles or approximates human language. If animals communicate with a system that is structured like human language, then language as we know it is not the unique property of our species. This chapter investigates the ways in which animal communication is like human language and the ways in which it is different. 16.1 Non-vocal communication One of the most striking things about animal communication is the variety of means through which it is carried out. Animals communicate not only with sounds but with scent, light, ultrasound, visual signs (see figure 16.1), gestures, colour, and even electricity. From the slime mold to the Kalahari barking gecko to the giant blue whale, all living things communicate. Some non-vocal modes of communication are described here. Scent Chemicals used by animals specifically for communicative purposes are called pheremones. Pheremones are used by species as different as molds, insects, and mammals. A female moth signals its reproductive readiness through the release of a pheremone into the air. Only a few of these molecules need to be sensed by a male moth for it to start flying zigzag upwind towards its potential mate. Dogs and other canines leave a urine-based pheremone as an identification mark to stake out their territory, and many non-human primates have specialized scent glands for the same purpose. © Pearson Education Canada 2008 514 16Ch16_OGrady.QXD 1/8/08 3:27 AM Page 515 Animal communication 515 Light Probably the most well-known light user in North America is the firefly or lightning bug. This small flying beetle uses light flashes in varying patterns to signal its identity, sex, and location. Different species of these insects have different and distinguishing light patterns. Electricity Certain species of eels in the Amazon River basin communicate their presence and territoriality by means of electrical impulses at various frequencies. Each species signals at a specific frequency range, and the transmitting frequencies, like those of radio and televi- sion stations, do not overlap. Colour The colour (or colour pattern) of many animals plays an important role in their identification by members of their own species and other animals. The octopus changes colour frequently and this colouring is used for a range of messages that include territorial defence and mating readiness. Posture This is a common communicative device among animals. Dogs, for example, lower the front part of their bodies and extend their front legs when they are playful. They lower their whole bodies to the ground when they are submissive. Postural communication is found in both human and non-human primates. Gesture Humans wave their arms in recognition or farewell, dogs wag their tails in excite- ment, and cats flick their tails when irritated. Many birds perform elaborate gestures of raising and lowering the head or racing back and forth across the water in their mating rituals. Some fish, such as the male stickleback, perform a series of distinct movements in the water as part of their mating ritual. Facial expressions These are specific types of communicative gestures. When a male baboon yawns, bares its fangs, and retracts its eyebrows, it is indicating a willingness to fight. A wide and recognizable variety of facial expressions is found among chimpanzees, a number of which are shown in figure 16.1. Experiments have shown that humans can classify the meanings of these expressions quite accurately. For example, when humans draw back the corners of their mouths into a smile, they are generally indicating co-operation. A non- human primate’s smile also indicates non-aggressiveness. Figure 16.1 Some chimpanzee facial expressions: a. anger; b. fear-anger; c. affection; d. frustration-sadness; e. playfulness Source: Adapted from S. Chevalier-Skolnikoff, “Facial Expression and Emotion in Nonhuman Primates” in E. Ekman (ed.), Darwin and Facial Expression (New York: Academic Press, 1973), pp. 11–90. © Pearson Education Canada 2008 16Ch16_OGrady.QXD 1/8/08 3:27 AM Page 516 516 Chapter Sixteen 16.2 Communication structure: the study of signs Certain common elements underlie the bewildering variety of communicative strategies found in nature. An understanding of these elements is necessary for comparing the differences and similarities among systems of communication. 16.2.1 Signs Communication relies on using something to stand for something else. Words are an obvious example of this: you do not have to have a car, a sandwich, or your cousin present in order to talk about them—the words car, sandwich, and cousin stand for them instead. This same phenomenon is found in animal communication as well. Instead of fighting over territory, for example, many animals produce sounds or make gestures that threaten and intimidate intruders—the message replaces the attack. Birds utter warning calls that repre- sent the presence of a threat. A threatening animal or human need not be seen by other birds before they take flight—perception of the warning call replaces visual perception of the threat. Each of these things that stand for other things is technically known as a sign. The sign is a unit of communication structure that consists of two parts: a signifier, be it a word, a scent, a gesture, or an electrical frequency, and something signified that exists in the real world, and which is mentally represented by the sign’s conceptual content. The real world can be thought of as external, mental, or emotional, and so what is signified by a sign can be as diverse as a tree, an abstract idea, a perception, or a feeling. Because their content is conceptual, all signs are associated with some meaning, such as ‘danger’, or ‘item of furniture with legs and a flat top’. Individual instances of signs are called tokens. For example, in the sentence The baby threw the rattle there are five word tokens, but only four signs; the occurs twice as a token, but it is the same sign in both instances. Figure 16.2 illustrates these distinctions. Sign Figure 16.2 A sign Signified /tri/ Signified ‘plant, having [tri] Token a trunk, ° with leaves or needles’ Real world referent The signifier A signifier is that part of a sign that stimulates at least one sense organ of the receiver of a message. The phonological component of the word tree, represented as /tri/ and pronounced © Pearson Education Canada 2008 16Ch16_OGrady.QXD 1/8/08 3:27 AM Page 517 Animal communication 517 Language Matters The Science of Semiotics Semiotics, the study of signs, is a field of study that links many diverse disciplines, among them linguis- tics, anthropology, philosophy, zoology, genetics, literary study, and computer science. An understanding of signs is essential for understanding how messages are transmitted. So that we can understand signs better before proceeding to an analysis of animal communication, the next section examines their structure in detail. To find out more, read Daniel Chandler’s Semiotics for Beginners at www.aber.ac.uk/ media/Documents/S4B/. [tri] is a typical linguistic signifier. A signifier can also be a picture, a photograph, a sign language gesture, or one of the many other words for tree in different languages. The signified The signified component of the sign refers to both the real world object it represents and its conceptual content. The first of these is the real world content of the sign, its extension or referent (see chapter 6, section 6.1.3) within a system of signs such as English, avian communication, or sign language. In our example, the referent is represented by a drawing because there is no room to include a real tree between the pages of this book. (Of course, the signifier /tri/ could also have a picture of a tree as its referent.) It is easiest to think of referents as concepts or persons or things but they may be ideas or feelings as well. The signified component of a sign also evokes an intension (see chapter 6, section 6.1.3) to users of the system in question. A word for ‘tree’ evokes concepts that probably include ‘plant’, ‘having a trunk’, and ‘bearing leaves or needles’ in the minds of speakers of any language who are familiar with trees. Some animals appear to conceptualize in terms of classes or categories as well. Certain monkeys, for example, distinguish among various types of predators on the basis of size, shape, and motion (see section 16.5.3). 16.2.2 Types of signs Signs can be divided into three basic types, depending on (1) whether the signifier naturally resembles its referent, (2) whether the signifier is directly linked with the referent in a physi- cal or mechanical sense, or (3) whether signifier and referent are arbitrarily associated.

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