Orangutans (Pongo spp.) do not spontaneously share benefits with familiar conspecifics in a choice paradigm

Abstract

Humans are thought to be unique in their ability to help others voluntarily even though it may sometimes incur substantial costs. However, there are a growing number of studies showing that prosocial behaviors can be observed, not only in humans, but also among nonhuman primates that live in complex social groups. Prosociality has often been described as a major factor that facilitates group living. Nonetheless, it has seldom been explored whether solitary living primates, such as orangutans, share this propensity. In the present study, we tested four captive orangutans (Pongo abelii × pigmaeus, Pongo pigmaeus) in a simple food-delivering task. They had a choice, incurring the same cost, between getting a food reward for themselves and providing an additional food reward to a conspecific recipient passively sitting in an adjacent booth. Two orangutans played the actor's role, and two orangutans participated as recipients. The results showed that the actors did not choose to deliver food to the recipients more often than expected by chance (51.3 % on average). The control condition demonstrated that this tendency was independent of the actor's understanding of the task. These findings suggest that orangutans do not spontaneously share benefits with other conspecifics, even when the prosocial choice does not disadvantage them. This study gives the first experimental evidence that socially housed captive orangutans do not behave prosocially in a choice paradigm experiment. Further studies using a different experimental paradigm should be conducted to examine whether this tendency is consistent with previous findings hypothesizing that the enhanced prosocial propensity shown in humans and other group living primates is an evolutionary outcome of living in complex social environments.

The nature of prosociality in chimpanzees

“…In the only test of instrumental helping in bonobos, there was no evidence of prosociality, with only the relatively solitary orangutans handing tools to distressed partners47. Other non- Pan ape species have shown no signs of sharing193056, evidence in Old World primates has been mixed, with self-regarding preferences for social contact as possible explanations for apparent prosociality2930575859. Among New World primates, capuchin monkeys have not consistently exhibited prosocial sharing1931606162 although see6364.…”

The comparative study of empathy: sympathetic concern and empathic perspective‐taking in non‐human animals

“…However, other studies have shown that chimpanzees do seem to help others even in contexts where there is food involved (Warneken & Tomasello, ; de Waal, Leimgruber & Greenberg, ; Yamamoto, Humle & Tanaka, ; Greenberg et al ., ; Horner et al ., ; Melis et al ., ; Yamamoto et al ., ; Claidière et al ., ). In some studies, orangutans ( Pongo abelii, Pongo pygmaeus ) (Amici et al ., ; Kim et al ., ), bonobos, western gorillas, spider monkeys ( Ateles geoffroyi ) (Amici et al ., ), cotton‐top tamarins ( Saguinus oedipus ) (Cronin et al ., ; Stevens, ), Japanese macaques (Burkart & van Schaik, ), and capuchin monkeys ( Cebus apella ) (Burkart & van Schaik, ; Drayton & Santos, ) did not show other‐regarding preferences. However, marmosets ( Callithrix jacchus ) (Burkart et al ., ; Burkart & van Schaik, ), capuchin monkeys (de Waal et al ., ; Lakshminarayanan & Santos, ; Brosnan et al ., ; Takimoto, Kuroshima & Fujita, ; Suchak & de Waal, ; Claidière et al ., ) and bonobos (Tan & Hare, ) were found to show other‐regarding preferences under different experimental conditions.…”

The evolution of altruistic social preferences in human groups

“…The Prosocial Test has now been conducted with chimpanzees from a number of different captive populations [49,51 -56], bonobos (Pan paniscus, [51,57]), gorillas [51] and orangutans [58] (Pongo spp. [58]).…”

“…[58]). In all these cases, apes did not choose the prosocial option more often in the test condition than in the control condition.…”