Many nonhuman primate species employ various types of ‘referential’ calls to conspecifics. These calls can be classified as food calls, predator alarm calls, and calls for aid (recruitment calls) (Tomasello and Call 1997). Gouzoules et. al. (1984:182) observed that juvenile rhesus macaques, while being attacked by another individual, used one of five different calls to recruit support from relatives. Gouzoules et. al. (1984:183) further grouped these calls as ‘noisy screams’, which are employed by high ranking individuals when there is physical contact, and ‘pulsed screams’ which are used when the attacker is a relative. When recordings of these calls were played during experimental testing, it appeared that individuals were responding to the acoustic properties of the calls, and not the behaviour or emotional arousal of the caller (Gouzoules et. al. 1984:190).
Gouzoules et. al. (1984:190) proposed that the ‘responder’ employed these acoustic properties to determine both the identity of the aggressor and what type of aggression was occurring. Gouzoules and Gouzoules (1995) later repeated this playback experiment with pigtail macaques, since they also appear to employ recruitment screams during agonistic contexts. They observed that the acoustic properties of these calls and the aspects of the agonistic situation differed from that of rhesus macaques (Gouzoules and Gouzoules 1995:449). However, they believed that there is no evidence that the calls of pigtail macaques encode the kinship status of the aggressor (ibid.).
The alarm calls of vervet and diana monkeys have been thought to ‘refer’ to features of the environment (Cheney and Seyfarth 1980, 1990, 1990a). Cheney and Seyfarth (ibid.) state that vervet monkeys employ three distinct predator specific alarm calls (leopard, eagle, snake). A loud barking call is given for leopards; a short, ‘cough like’ call is given for eagles; and a ‘chutter’ call is given for snakes (Cheney and Seyfarth 1990; Hauser 1996). Each call (stimulus) elicits a different escape (behavioural) response on the part of the receiving conspecifics (leopard alarm calls - run up the nearest tree; eagle alarm calls - look up, run into the bushes; snake alarm - stand on hind legs and look down at the ground) (ibid.).
However, it is assumed that this type of referential acoustic behaviour differs from the human usage of words for the following reasons (Seyfarth and Cheney 1997:252): 1) alarm call meaning appears to be limited to the connection between referent and sound; 2) alarm calls are difficult to specify; and 3) may be the result of simple conditioning. Seyfarth and Cheney (1997:252) state that although vervet calls function in a rudimentary semantic manner, it is uncertain whether vervets recognize the referential relation that exists between their calls and features of the environment. Additionally, it is uncertain whether or not this vocalization is interpreted as a representation of the caller’s knowledge of conspecifics (ibid.; Hauser 1996:413).
The alarm calls of male diana monkeys show consistent differences in acoustic and temporal structure depending on whether they are given to leopards or eagles (Zuberbühler et. al. 1997:602). According to Zuberbühler et. al. (1997:602), the most salient feature of these alarm calls, the number of syllables, did not seem to be sufficient for an unambiguous identification (for the human observers). The alarm call for leopards seemed to have fewer syllables than the alarm call for eagles, although there appeared to be some overlap (ibid.). The female and juvenile diana monkeys responded in qualitatively and quantitatively similar ways to both the male’s call to a predator and to the predator that typically caused that call, in both playback experiments and natural conditions (ibid.). Zuberbühler et. al. (1997:602) concluded from this observation that that these calls contain semantic information. Like vervets and diana monkeys, playback experiments with ring tail and ruffed lemurs indicate that they employ referential calls in specific, aerial or terrestrial, predator situations (Macedonia 1990).
In the case of the great apes, there have been no systematic studies with regard to how individuals understand or employ alarm or recruitment calls (Tomasello and Call 1997). Almost all of the systematic research concerns the food calls of chimpanzees: pant hoot, food grunt and ‘food-aaa’; but only the first two have been systematically studied (ibid.). Clark and Wrangham (1994:199) found that pant hoots given by food discoverers did not increase the frequency with which conspecifics arrived at the food site. Hauser et. al. (1993:818) found that chimpanzees used pant hoots in addition to food grunts when the amount of food was large. However, the function of pant hoots is uncertain, since it has been observed in other social situations, such as excitement or the announcement of an individual’s location (Mitani and Nishida 1993; Tomasello and Call 1997). According to Tomasello and Call (1997:257), pant hoots do not indicate the discovery of food since captive chimpanzees pant hoot in full view of conspecifics, even though all individuals are aware of the food source.
According to Hauser (1996) and Tomasello and Call (1997), the type of referential behaviour described in the preceding paragraphs, may be due to an innate mechanism, and does not necessitate any understanding of ones conspecifics. This mechanism enables these particular animals to generate specific noises in the presence of particular visual or emotional stimuli and to respond in certain ways to particular acoustic or visual stimuli (ibid.). However, this would be true of any type of behaviour, once it is broken down into components and taken out of context. One of the problems with this type of reasoning is that it ignores the overall picture (referential communication) in favor of a behavioural model.
Girneys
Most of the research conducted on free ranging nonhuman primates has addressed alarm calls. However, Locke (1998:194) has suggested that a more interesting class of vocalizations would be produced by contented animals, vocalizing quietly among themselves in a family or small group situation. One type of vocalization that is not screamed, but uttered by various species of monkeys is the girney. Girneys are most frequently produced by mothers who are interacting with other mothers or juvenile females. Girneys seem to be “produced behind closed lips and resemble the sound of an individual who is talking with food in his mouth” (ibid.). Girneys may be issued interchangeably with lip smacking, and are common among animals which live in small, intimate groups. From a physical standpoint, they lack the “rhythm of lip or tongue smacking, but are typically phonated” (Locke 1998:195). Locke (1998) has proposed that if the phonatory aspect of girneys were combined with the pulsatile character of lip and tongue smacking, a human like type of sound making could have been achieved.
