The adaptive functions of food transfer from parents to their offspring have been
explained mainly by two mutually non-exclusive hypotheses: the nutritional and informational
hypotheses. In this study, we examined the functions of food transfer in wild Javan
gibbons (Hylobates moloch) by testing these hypotheses from both infants' and mothers'
perspectives. We observed 83 cases of food solicitations that resulted in 54 occasions
of food transfers in three groups over a 19-month period in Gunung Halimun-Salak National
Park, Indonesia. Infants initiated all solicitations directed at their mothers with
one solicitation towards a father. Food solicitation rate decreased as infant age
increased and ceased before weaning. As predicted by the informational hypothesis,
infants solicited more food items difficult to obtain and preferred by their parents.
On the contrary to the nutritional hypothesis, infants solicited low-quality items
more often than high-quality items. Mothers did not change probability of food transfer
according to the food characteristics or infant age. Hence, our results suggest that
the primary function of food transfer from mother to infant Javan gibbons seems to
be information transfer rather than nutritional aids, similarly to great apes.