Adult Male Sociality and Reproductive Tactics among Orangutans at Tanjung Puting

Abstract

During a 4-year period at Tanjung Puting Reserve, Central Indonesian Borneo, adult male orangutans were observed for 2,670 observation hours as focal individuals. Adult male sociality centered around females. Almost the entirety (90%) of adult male participation in social groupings consisted of consortships. If time spent with recent consort partners is included, then adult males spent 95 % of the time that they were in social groups with consorts. Otherwise adult males were quite asocial. Adult males were totally intolerant of each other. Only two brief encounters between lone adult males occurred although avoidance of contact was seen 14 times. Another two encounters between adult males in the presence of females involved much aggression and included a lengthy combat in which the male consort defeated another adult male. Thirty copulations involving adult males were seen; only one copulation was a resisted mating. The other copulations all occurred in consortship. Ten consortships were seen; three involving adult females. While subadult male reproductive tactics predominantly consist of sneak/’rape’, adult male sexual strategy consists primarily of consort/combat tactics. Thus, adult males are interested in attracting and guarding receptive, fertile females. For this reason, wild adult males are relatively selective in choice of consort partner and may reject small proceptive adolescent females.