Male–immature interactions seem to depend on group composition in white-headed langur (Trachypithecus leucocephalus)

Abstract

In primates, male–immature interactions are always multifacetted. We studied male–immature interactions of white-headed langur during our long-term study in Nongguan White-Headed Langur Reserve, Guangxi, China. Male–immature interactions obviously differed between one-male groups and male–immature groups. In one-male groups, adult males behaved tolerantly or aggressively towards immatures and never carried out sociopositive behaviors. Sexual selection theory supports this phenomenon because males are predicted to bias to compete for more mating chances but not to invest in any single offspring. In male–immature groups, however, adult males carried out sociopositive behaviors and never behaved aggressively towards immatures. This is supported by kin selection theory because it will be beneficial for the males to increase the survival of the immatures if they are likely the fathers of them. Thus, we conclude that male–immature interactions differ between one-male groups and male–immature groups because the mating status of males are different between the two kinds of groups.