Communication is a two way process, there is one signaller and one receiver. There are four components in communication systems these are: signal, motivation, meaning and function (Smith, 1977) 1 Signal is a form of communication, it includes the senses e.g. touch, body postures. When a juvenile primate feels threatened crouches down, pulls lips back, making short grunts as an unrelated adult approaches. If the adult returns grunts and touches his shoulder the juvenile returns to his previous activity, because he has been reassured no threat is present. Meaning derived from the signaller depends on the interpretation of it and the context it is given in. If signals given in context specific patterns, the reactions of receivers can be observed to analyse how the meaning is determined. Age, experience, relationship and the history of an actor are all variables of the meaning of signals, these influence the response of the same signal, even at the same time.
Communication is used by primates to indicate information on different topics e.g. to identify mating partners of suitable species, sex , reproductive conditions, avoiding predator’s and defending territories. There are four main modes of communication that may be used for discovering this information: tactile, visual, olfactory and vocal communication. They can be used alone or as combinations. Tactile communication is related to touch, primates are considered to be very physical creature, juveniles grapple (wrestle) with each other while playing and group members groom each other with hands and mouths or reassure each other with touches and hugs when feeling threatened by predators. E.g. As discovered by Smuts and Watanabe, 1990 Baboons that are unrelated allow coalition partners to grasp their testicles, this is a strong indicator of trust and solidarity. In sexual interactions physical contact plays a central role, male Hamadryas baboons gently bite necks of their mates and male Bonobo’s push and pull bodies of their mates into more comfortable positions (Savage-Rumbaugh et al, 1977). The duration of sexual interaction varies widely among different species, but a variable exists of interruption. Mating is quicker if a high risk of being interrupted is present. In cases of aggression reassuring contact is used and to reconcile with each other after a conflict has occurred, conflicts are very hazardous as if physical violence follows minor wounds may lead to infections to develop which may lead to death especially in the humid tropics.
Primates use their body postures for visual communication, their eyes are forward facing which allows vision for depth perception. Facial signalling has been restricted to monkeys and apes, Prosimians have a limited capacity of facial expressions due to the fact that their lips are joined to their gums, hence why they have fewer nerves in their facial muscles (Zeller, 1987). Visual signalling is only useful during the daylight as during the night they cannot be seen. It expresses the emotional state of the signaller to others in the group, but some primates can send deceptive signals. An observation was carried out by Dewaal in 1982, in Arnhem zoo where a male chimpanzee used his hands and feet to cover fear, a grimace had settled on his mouth, so as not to signal submission to his challenger. 2 His effort to conceal his fear indicates voluntary control to hide an involuntary response.
Olfactory communication involves the sense of smell, all primates, including humans respond to odours, although they are not as strong in humans. Odours can be detected when the signaller is present even indirectly from the odours a signaller has left behind in certain area. Odours tend to consist of fatty acids that bacteria has produced as a reaction to hormones, they are secreted from different parts of the body where glands are present. This type of communication also transmits the reproductive condition of a female, her identity, age and sex (Zeller, 1987). This type of signal is passive as odours are given off while primates go about their everyday lives. Females present their genital regions to males for inspection, the males carry this out by sniffing and licking the area, it provides a olfactory cue on the females ovulatory condition (Michael et al, 1972).
The last mode of communication is vocal and it differs among species, therefore this allows primates to distinguish between members of their own kind. This needs to be done to find mates. Chimpanzee screams are of lower frequency than a high frequency of Bonobos this is due to the difference in size of their vocal tracts (Mitani, 1996). The ability to distinguish calls is important for defending territories and avoiding predators. When communicating the whereabouts of primates long-distance calls are used so different groups can avoid each other to who is calling and their location. E.g. Male orang-utans make long distance calls to warn away male intruders and attract oestrus females. Female and male howler monkeys calls are different , due to size of their bodies and size of the hyoid bone (amplifies long calls). E.g. Vervet monkey mothers respond more strongly to calls of distress from their own offspring, hence they can detect their relationship to the signaller, in the same way humans can recognise voices of individuals they are familiar with, (Cheney and Seyfarth, 1990).
Discovering what signals mean among primates remains yet to be discovered, humans have attempted to teach monkeys to speak but have miserably failed. Scientists need to acknowledge that a different primate cannot be taught what we know due to the wide differences that exist between us. They need to be analysed without references to humans, only then will we have a greater understanding of their social lives and cognition processes.
1 Strier, K. ‘Primate Behavioural Ecology’ . Allyn and Bacon 2000. Pg. 275
2 Strier, K. ‘Primate Behavioural Ecology’ . Allyn and Bacon 2000. Pg. 278-281
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