Abstract: Food sharing , defined as allowing others to eat part or all of oneπs own monopolizable food items, is one of the important social interactions in non2human primates. It happens mostly between adults and immatures but rarely among adults, with a common pattern of passive food sharing. Researches on food sharing in non-human primates were reviewed along this two age categories focusing on their characteristics and functional explanations. Food sharing between adults and immatures typically happens between mothers and their offspring, and ecological factors including age of the immatures and the quality and quantity of food, influence the frequency of food sharing. As an important part of infant care, the functional significance of food sharing was usually explained with foraging assistance hypothesis and food learning hypothesis. The mechanism of food sharing is more complex among adults than between adults and immatures, for that it is influenced not only by ecological factors but also by social factors, such as affinitive relationship and social dominance between individuals , as well as social tolerance in the group. As two of the popular explanations for non-kin food sharing among adults, reciprocity explanation and harassment explanation were compared. Reciprocity explanation focuses on the alternation of donor and recipient roles in repeated food interactions and states that an individual may benefits another by relinquishing part of its own food if the recipient returns the favor later. On the other hand, according to harassment model, the owner may allow the beggar to consume a fraction of the food, since the beggarπs harassment is costly. It is suggested that reciprocity requires complex cognitive skills , while harassment has very few constraints and thus should be a better model. In the end, it was proposed that food sharing could be taken as an ideal context in further studies on the social cognition of non-human primates, and researches on food sharing could provide insights into the understanding of the evolution of human cooperation.

Key words: Food sharing; Non-human primates; Reciprocity; Harassment