Formation and development of a group of juvenileHylobates Iar

Three young gibbons, who had minimal previous social contact with each other, were released together in a semi-natural environment. The individual and social behavior of the gibbons paralleled that of gibbons in the wild: of the total daytime, 71% was spent in foraging activities, 20% in social interaction, and 9% in inactivity.The tendency toward group formation proved strong in these gibbons; they were together an average of 68% of the time following their release. Group maintenance seemed based on a sharing of the dominance role for various activities, either equally among the three or in the form of a pair (the male and one of the females) being co-dominant. The male and small female became gradually isolated from the large female. Reciprocal initiation of sexual exploration and play were related to this pairing.The results of discrete activity observations by the simple method of simultaneously recording geographical location and activity of each gibbon, plus the continuous observation of social behavior, were remarkably consistent with gibbon observational data in an artificial setting and those obtained in long-term field investigations. In addition, the methodology permitted an analysis of some of the finer aspects of social behavior.