Abstract
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.
Highlights
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
The main predictions of the nutritional hypothesis are that food transfer will be most frequent during the weaning period, and that nutritionally rich food items will be transferred more than nutritionally poor items
We examined the functions of food transfer in wild Javan gibbons (Hylobates moloch) by testing the nutritional and informational hypotheses
Summary
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. Callitrichid parents actively participate in care-giving and food-provisioning to offspring to facilitate weaning process, and thereby shift their investment (e.g. energetic burden of lactation) from current to future offspring In such a case, reproductive benefits to the parents are likely to exceed the cost of food provisioning to infants[15,16]. Food preference in observational studies often defines preferred food as food items that are eaten more frequently than their relative abundance[33] Following this definition, we considered the parental food preference as another potentially important factor for the informational hypothesis and predicted that preferred foods would be solicited more to facilitate information transfer. Solicitation for novel food items is rejected more often than solicitation for familiar food items in captive lion tamarins (Leontopithecus spp.)[6]
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