Do capuchin monkeys willingly share food with a conspecific? (#56)
Although prosocial behaviours are commonplace in human societies, their cognitive mechanisms and evolutionary roots are yet to be explained. Studies of pro-sociality in great apes, involving food sharing tasks, suggest that altruistic food sharing may be a uniquely human characteristic (Tian et al., 2013; Bullinger et al., 2014). However, tufted capuchin monkeys (Cebus apella), a New World species diverged from apes about 40 million years ago, which have been shown to be sensitive to others’ welfare (Takimoto et al., 2010), remain untested on this question of altruism. To investigate capuchins’ food sharing capacities, 12 pairs composed of a benefactor and a partner were tested in two adjacent compartments. We observed whether the benefactor monkeys (those in possession of food) would benefit their partner by voluntarily delivering them food. In the first experiment the cost of sharing was high; benefactors had to allow their partner to eat a portion of their own food (altruistic sharing). In the second experiment the cost was reduced so that the benefactors no longer had to share their own food but inaccessible one (active giving). The results suggested that capuchins were unwilling to share food altruistically. However, when the cost of sharing decreased, they sometimes chose to act pro-socially toward selected individuals. The results will be discussed in line with previous ape studies reporting that partners’ behaviours may also play an important role for pro-sociality to appear, by driving the benefactor’s response (Yamamoto et al.,2009).