On the genesis of a group of Siamang.

Abstract

AbstractA population of siamang in lowland dipterocarp forest at Kuala Lompat, Pahang, Malaysia, was studied discontinuously between April 1969 and November 1971. Between March and May 1970 a sub‐adult male in the main study group became increasingly peripheral. The frequency of aggressive interactions with the adult male increased, and the sub‐adult played a greater part in group calling sessions. These changes coincided with the onset of sexual activity between the adult pair.By October 1970 the sub‐adult male had left the group, established a territory in an adjacent vacant area of forest, and been joined by a young adult female. A second, older female joined the new group in April 1971, left it again in July, and returned in September. Social relations within the new group were unstable, and its activities were less coordinated than that of the old group.It is suggested that the intolerance of the adult male during a period of reproductive activity, together with the maturation of the sub‐adult, were the crucial factors in the latter leaving the group, and that the sub‐adult's increased participation in group calling played a part in attracting females.