C. Borries et al., Males as infant protectors in Hanuman langurs (Presbytis entellus) living in multimale groups - defence pattern, paternity and sexual behaviour, BEHAV ECO S, 46(5), 1999, pp. 350-356
Hypotheses about the evolution of gregariousness and social organisation in
primates are based on ecological explanations as well as on social factors
such as conspecific threat (especially infanticide by males). The social e
xplanation fits well with the conditions found in strepsirrhine primates an
d furthermore explains why infanticide in anthropoid primates living in one
-male groups mainly occurs when the resident male (protector) is replaced.
However, whether it likewise fits to the conditions in multimale groups wil
l depend on the role Of resident males as infant protectors, which has rare
ly been examined. We investigated long-term data of wild Hanuman langurs (P
resbytis entellus) inhabiting a forest near the village of Ramnagar (southe
rn Nepal). Twenty-two eye-witnessed attacks on infants by males were analys
ed in connection with male residency, paternity (DNA analyses) and sexual b
ehaviour. Adult males played a major role in infant defence (65%). Only the
genetic father or males who had been residents when the infant was conceiv
ed were observed to protect infants. Males who immigrated after a. female h
ad conceived may later attack her infant and were never observed to defend
it. It seems that the males took only copulations with potentially fertile
females but not with pregnant females as clues for paternity. In the light
of these results it seems likely that the risk of infanticide is an importa
nt determinant in female-male associations even in anthropoid primate multi
male groups.