In this article we will discuss about:- 1. Meaning of Communication 2. Who benefits from Communication ? 3. Components 4. Modes.
Meaning of Communication:
Animals convey information to other animals of its own species as well as other species, through an incredible diversity of sounds, colours, odours, postures and flashing lights. Communication is defined as the transfer of information from a signaler to a receiver.
It is the active transfer of information through signals. Signal is a trait, or part of a trait, that evolved solely in order to convey otherwise unknown information to other individuals. For example, the song of a male white crowned sparrow (Zonotrichla leucophrys) is specific not only to the species, but also to an area and to the individual.
The male, by singing, not only warns neighbouring males, but may also provide potential mates with information about his health, his social status, and even his place of birth.
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Information may also be collected by observation, however, such information is not communication. Ethologists through extensive field observations have found that communication behaviour occurs in regular patterns that recur nearly unchanged from event to event. Such sequences are referred to as fixed action pattern (FAP).
Who benefits from Communication ?
It is a matter of question as to who benefits from communication—the sender, the receiver, or both. Ethologists have argued that both benefits from a communication. Although both sender and receiver do frequently benefit, it is the sender who may sometimes benefit at the expense of the receiver. For example, when a parent bird uses a broken wing distraction display to lead a predator away from her young.
The definition of communication given by Slater (1983) is “the transmission of a signal from one animal to another such that the sender benefits, on average, from the response of the recipient”. Communication from sociobiological viewpoint assumes that natural selection acts primarily at the level of the individual.
Therefore, communication is a mean by which the sender manipulates others for his or her own benefit, like that of advertising. The sender, through displays, can control the behaviour of the receiver with a minimum energy waste. In such a case, exaggeration and redundancy are the rule. Displays are done in such a manner so as to increase their persuasive power and not to maximise information transfer.
Basic Components of Communication:
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According to Ewsbury (1978), any communicating system comprises of seven essential components, such as:
1. Signaller:
The member who gives off a signal.
2. Receiver:
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The individual who receives the signal.
3. Message:
The behaviour emitted by the signaller.
4. Channels:
It is the pathway through which normally a signal travels.
5. Noise:
Background activity emitted and transmitted in the channel which is not related to the signal.
6. Contacts:
It is the particular setting in which a signal is emitted, transmitted and received.
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7. Code:
It includes complete set of languages of possible signals and contexts.
Modes of Communication:
In the modes of communication there are physical forms used to transmit signal from sender to receiver. These, from an evolutionary perspective, have costs and benefits associated with different modes, depending on the environment and the nature of information transmitted. Table 5.2 depicts costs and benefits of four major modes of signal transmission.
A. Chemical signals:
The earliest form of communication is thought to be chemical, as odour is used throughout the animal kingdom, except birds. Substances that can be picked up by the sense of smell are pheromones, produced by special glands. Most pheromones are involved in mate identification and attraction, spacing mechanism or alarm.
Chemical signals have evolved widespread because such signals can transmit information in the dark, can travel around solid objects, can last for hours or days and are efficient in terms of the cost of production. As these pheromones diffuse through air or water, they are slow to act and have a long ‘fade-out’ time.
B. Tactile communication:
Tactile communication are short-range communication in the form of actual physical contact or touch. The effectiveness of tactile communication is limited by distance as one animal must touch another in order to convey information. Its advantage is that it can be carried out even in totally dark conditions and they have a short ‘fade-out’ time.
Tactile signals are used extensively in social bonding, infant care, grooming and mating. This type of signal is directly correlated to the sensitivity of their receptors. Antennae are used by sub social insects, such as cockroaches and by social insects such as bees. Much of the information about the type and location of food comes from tactile communication.
Probably the most widespread use of tractile stimuli occurs during copulation. Vaginal stimulation in some mammals induces ovulation. In rodents, the stimulation of the back end of an oestrous female produces concave arching of the back and immobility (cordosis).
Another widespread use of tactile stimuli is grooming. In most primates, it is an important social activity. It functions not only in the removal of ectoparasites but also as a “social cement” in the establishment of social bonds. Members of an ant colony constantly tap and touch each other which activate and strengthen the ants’ social bonds.
C. Auditory Communication:
Sound is the most used form of communication in animals, as information about immediate conditions can be transmitted faster. The advantage of sound is that it can travel around objects, through dense vegetation and it can be used in the dark.
The deer gives alarm calls for approaching tiger; male frogs call to attract females; bats use echolocation for hunting; birds’ song serve for both territorial and courtship functions; other animals use sounds to communicate danger, reproductive readiness and species recognition.
Information can be conveyed by both frequency and amplitude modulation. Some animals, e.g. bats, can make use of ultrasounds which are out of range of human ear. Howler monkeys (Alouatta sp.) in the neo-tropical rain forest use resonating air chambers to signal other groups with low-frequency calls. On the other hand, squirrel monkeys (Saimiri sciureus) use higher-frequency sounds, which dissipate rapidly.
Sound can be produced by a single organ. Animals produce sound with the help of various organs. Animals such as mammals, birds, reptiles and amphibians produce sound with the help of vocal cord. Some frogs, toads, howler monkeys, and gibbons have resonating air chambers that even help them amplify the sound signals.
Spiders and some insects like crickets are instrumentalists, that is, they produce sounds by tapping, scrapping, bending, chirping, or rubbing parts of their exoskeleton.
Grasshoppers scrape a comb on the hind appendages across the surface of the front wing. The death head catter-pillar makes a series of loud snapping noises much like electrical sparks, when handled. Fishes make sound by vibrating their swim bladders. Rattlesnakes vibrate their hard dried scales at the tip of the tail, which makes a rattling sound. Humming bird hums by beating its wing very fast.
Underwater sound is produced by fishes and aquatic invertebrates, which are of different nature. Marine mammals produce clicks, squeals etc. which are more complex sounds that incorporate many frequencies. Baleen whales produce lower and longer sounds than do toothed whales.
Certain sounds of very low frequency might also have seismic properties. Desert rodents, such as kangaroo rats, have greatly inflated middle ears which make them sensitive to low-frequency sounds and vibrations.
Both Asian elephants (Elephas maximus) and African elephants (Loxodonta Africana) use very low frequency rumbles in the range of 14-35 Hz to communicate over several km distances. Such infrasonic sounds have very high pressure levels and suffer very less environmental attenuation and are used for long-distance coordination of group movements and location of mates.
D. Surface waves:
By patterns of surface vibrations, information can be conveyed. Males of Gerris remigis (a species of water – strider) send out ripples at a certain frequency. The receptive female responds by moving toward the source. As the female gets within a certain distance, the male switches to courtship waves.
E. Electric field:
Some fishes like sharks etc., have electroreceptors that they use either passively or actively for detecting objects including food and in communicating socially. In addition to electro-locating objects, electric fishes communicate information about species identity, individual identity and sex, by modulating the shape of the electric organ discharge.
By altering either the wavelength or pulse duration, electric fishes can communicate threat, warning, submission; maintain group coordination in schools etc. The advantage of this mode of communication is that it can be useful in dark, murky waters; it can travel around and even through certain objects; and it provides information on exact location.
F. Visual communication:
Visual communications are done through light signals detected by the eyes. The visual displays enable the receiver to locate the signaler precisely in time and space. Gestures, postures, facial expression, raising of hair, courtship, colour change and aggressive displays in many fishes, amphibians, reptiles, birds and mammals are some good examples of visual communication.
Visual communications may be categorized into two types:
(a) Badges:
It involves colour and shape of the animals and also the morphology (fur, feathers etc.).
(b) Displays:
In this case the animals act or do things to communicate certain behaviour patterns. The flashes of fireflies are emitted through specialised photogenic tissue in the abdomen. Such flashes are related to mate attraction. Each species has its own flash code.
The flashes of males vary in intensity duration and interval in a species-specific way. The flash interval varies within a species, depending on whether the male is searching for a female or courting the one he has found. The females of a particular firefly species (Photuris versicolor), after mating, may mimic the flash response of closely related female species, luring the males toward her and then devour them.
Honeybees communicate the location of food sources by waggle and circle dance, when they return back to the hive. This dance informs other bees about the direction, distance and type of food source.
Fishes and some invertebrates are able to change colour within few seconds by expanding and contracting chromatophores beneath the skin.
Facial expressions in higher animals are used as forms of communication. Primate eyes have exceptionally good capability of perceiving very small movements and small differences in shapes.
Although visual communication has the advantage of quick transmission, none-the-less it has the following limitations:
1. Visual communication cannot be sent long distances particularly through dense forest.
2. Colours attract predators. Therefore, these colours are kept hidden by the bearers and are only flashed when needed. This may cause delay in action.