Adult bonobos show no prosociality in both prosocial choice task and group service paradigm

Abstract

Previous studies reported contrasting conclusions concerning bonobo prosociality, which are likely due to differences in the experimental design, the social dynamics among subjects and characteristics of the subjects themselves. Two hypotheses have been proposed to explain the occurrence of prosociality in animals: the cooperative breeding hypothesis and the self-domestication hypothesis. While the former predicts low levels of prosociality in bonobos because they are non-cooperative breeders, the latter predicts high levels of prosociality because self-domestication has been proposed to select for high levels of tolerance in this species. Here, we presented a group of thirteen bonobos with two platform food-provisioning tasks: the prosocial choice task (PCT) and the group service paradigm (GSP). The latter has so far never been applied to bonobos. To allow for free choice of participation and partner, we implemented both tasks in a group setting. Like in previous PCT studies, bonobos did not choose the prosocial option more often when a group member could benefit vs not benefit. In the GSP, where food provisioning is costly, only subadult bonobos showed a limited amount of food provisioning, which was much lower than what was previously reported for chimpanzees. In both experiments, adult subjects were highly motivated to obtain rewards for themselves, suggesting that bonobos behaved indifferently to the gains of group members. We suggest that previous positive food-provisioning prosociality results in bonobos are mainly driven by the behaviour of subadult subjects. The lack of prosociality in this study corresponds to the hypothesis that proactive food provisioning co-occurs with cooperative breeding and suggests that proactive prosociality might not be part of the self-domestication syndrome in bonobos.

Prosociality in a despotic society

“…We discussed how kin favoritism and dyadic social tolerance in a despotic society could drive prosocial motivations. Although we did not find the age difference of the individuals to influence prosociality significantly, participation of a relatively large number of juveniles can not be neglected; for instance, due to their higher social tolerance, bonobo sub-adults have been shown to be more prosocial than adults (32). Nonetheless, prosociality was not restricted to juveniles, and therefore, we speculate on the role of complex socio-ecological and living conditions in facilitating individual prosocial motivations.…”

“…The fact that active solicitation and the presence of individuals being potential receivers did not necessarily elicit prosociality also indicates its proactive nature. For instance, active solicitation, begging or signal prompting has been argued to be a stimulus enhancement mechanism of rather "reactive" prosociality (19,31,32). In contrast, some studies even found a negative role of signal prompting on prosociality (34)(35)(36).…”

“…Yet, previous studies found no evidence of prosocial tendencies in Japanese macaques in captivity (3, 10). The current study uses a well-established group service food provision paradigm (3, 5, 9, 10, 32) (see Figure 1 ) to explore prosociality in semi-free-ranging Japanese macaques. Our research offers several advantages over the previous studies on (Japanese macaque) prosociality – (a) a semi-free-ranging group with naturalistic conditions, i.e., high ecological validity, (b) a relatively large sample size; i.e., a group of over 170 macaques, out of which 25 participated in our experiment voluntarily ( Table S1 ), (c) individual-level representation of prosocial motivations (if any), and (d) both group level- as dyadic social tolerance measures.…”

Behavioral and physiological response to inequity in bonobos (Pan paniscus)

“…While the majority of IA research in great apes has focused on chimpanzees, bonobos make a very interesting study species to investigate advantageous and disadvantageous IA. Bonobos are often said to be very peaceful, tolerant, prosocial, and empathic (Furuichi, 2011; Hare et al, 2007; Maclean, 2016; Parish et al, 2000 but see Cronin et al, 2015; Jaeggi et al, 2010; Stevens et al, 2008; Verspeek et al, 2022), and have been shown to cooperate in experimental food retrieval studies in the lab (Hare et al, 2007; Nolte & Call, 2021). Under the cooperation hypothesis it could be expected that IA may be equally expressed in bonobos compared to chimpanzees.…”

“…Similar to chimpanzees, bonobos are a male‐philopatric species, meaning that males stay in their natal groups, while females migrate to other communities when they reach maturity (Hashimoto et al, 2008; Kano, 1992). Unlike chimpanzees however, female bonobos engage in strong cooperative bonds among each other as well as with their adult sons (Hohmann & Fruth, 2002; Parish, 1994; Stevens et al, 2006; Surbeck & Hohmann, 2008), resulting in high value relationships between females, but not between males (Stevens et al, 2015; Verspeek et al, 2022). Males on the other hand do not form strong bonds among each other and only rarely engage in cooperative interactions (Hohmann & Fruth, 2002; Ihobe & Furuichi, 1994; Kano, 1992; Surbeck et al, 2017), and show low value relationships (Stevens et al, 2015; Verspeek et al, 2022).…”