Intergroup Spacing Research Articles

Individual Recognition, Intragroup Cohesion and Intergroup Spacing: Evidence From Sound Playback To Forest Monkeys

AbstractThe contexts and functions of several loud mangabey vocalizations, particularly the "whoopgobble", were investigated observationally and experimentally. Whoopgobbles are notable for their audibility and distinctiveness over long distances, their temporal pattern of delivery, and particularly their stereotypy and individual distinctiveness. On the other hand, contexts of and responses to these vocalizations are variable and sometimes nonobvious. In order to control context and more systematically investigate response, an experimental method involving playback of recorded vocalizations was developed. Although precautions against habituation were necessary, mangabey responses to playbacks were clearcut and repeatable. Answering vocalizations, changes in group movement, and changes in the dispersion of individuals within a group occurred only in response to mangabey vocalizations. Whoopgobble playbacks provoked a pattern of response, including most notably the rapid approach of one adult male (the "RA" male) from each group, which was specific to this call. Playback of whoopgobbles between 100 and 600m from mangabey groups indicated that this call does transmit information regarding the identity of the vocalizing individual and group over these distances. Test groups moved away from neighboring- and unknown-group calls, but towards those of their own males - particularly those of RA males. RA males, on the other hand, do not approach calls of other males from their own groups. Within a group, whoopgobbles may thus increase cohesion and influence the direction of movements. Characteristics of whoopgobble form and context are discussed with regard to hypothesized functions of these and other forest monkey loud calls. Responses by free-ranging mangabeys to playback of the whoopgobble confirm its role in maintaining distance between groups. Response was found to be independent of group size, despite the fact that whoopgobble rate is closely related to this variable and thus could transmit such information. Since responses were also found to be independent of location within the home range, intergroup spacing among mangabeys appears not be be "territorial", site defense does not occur. Nevertheless, the central areas in at least some mangabey groups' home ranges were never penetrated by neighbors. Playback tests with black-and-white colobus and blue monkeys, among which territorial spacing has been reported, indicate that responses to loud calls have some degree of site-specificity among these species. But the mangabey pattern of intergroup spacing appears to result from a combination of low group density, site attachment within groups, and site-independent avoidance between groups. These results emphasize that spacing "system" and "pattern" are not necessarily equivalent; a given set of spacing behaviors can result in different spacing patterns under different ecological conditions, while a given pattern may be obtained by any of several behavioral means. Evidence for site-independent spacing in other primate species is discussed.

Cerococebus albigena: Site Attachment, Avoidance, and Intergroup Spacing

Intergroup spacing of free-ranging mangabeys, Cercocebus albigena, was investigated by observation of group movements and intergroup behavioral interactions in western Uganda between 1971 and 1974. This omnivorous, arboreal species distinguishes itself from many other forest monkeys by its large home range and seminomadic pattern of movements. Although site attachment seems to be slight, its existence can be demonstrated by comparison of group movements with random-walk predictions. Frequency of intergroup encounter is extremely low; approaches involving visual contact between groups were observed only once in 120 days of systematic following. Interaction frequency can be compared with that predicted by a simple "gas" model of independent movement; encounters were found to be considerably rarer than expected. Simultaneous observation of neighboring groups' tracks indicates that groups tend to avoid each other by mutual withdrawal when they detect each other within about 500 m. Avoidance between groups is often accompanied by rapid approach and "monitoring" by certain adult males (christened RA males) which may interact directly with members of the opposing group but more commonly remain nearby but out of sight. Mutual avoidance occurs irrespective of the relative sizes of the interacting groups and of the location of the encounter relative to home-range centers. Existence of this avoidance-based spacing system may be favored by the irregular temporal distribution of major food resources, which has been documented in this study area. The relevance of the RA males' behavior to the maintenance of such a mutually reciprocal system is discussed.

Vocalizations of East African Monkeys Ii: Black and White Colobus

AbstractSix sound patterns are important in social communication of the black and white colobus, Colobus guereza, in the Budongo forest, Uganda. The loud roaring of adult males seems to function in intergroup spacing. The snort of adult males may be a threat or an alarm. A soft purring, rarely heard, accompanies a group movement. A cawing sound is used by adult females, juveniles, and infants in situations of mild distress or threat. Squeaks and screams are used by adult females, infants, and juveniles in acute distress. A non-vocal sound, the tongue click, is employed in territorial defense. The characteristics of these sounds are interpreted in light of the social organization of this species which is territorial, with an average group of eight animals, typically with only one adult male. Signals used primarily in intertroop communication are discrete, while those used for signalling within the troop are graded.

Spatial factors and the behavior of nonhuman primates.

Spatial factors in the environment and their influence on the behavior of nonhuman primates are reviewed. Intragroup spacing is discussed in terms of interindividual distance and spatial patterning. Home range versus territorial intergroup spacing mechanisms are described, and the role of ‘cover’ in determining interindividual distance and communication is discussed.