Liza Moscovice was awarded a Leakey Foundation Research Grant during our fall 2016 cycle for her project entitled “Explaining patterns of within and between-group cooperation among LuiKotale bonobos.”
Bonobos (Pan paniscus) exhibit high levels of cooperation within and between communities that is not consistent with traditional evolutionary models. Female bonobos are the dispersing sex and most leave their natal communities around sexual maturity. After immigrating into a new community, females are very social and form both short-term and long-term friendly relationships with other females who are not genetically related. Females also participate in cooperative alliances with a wide range of partners to co-defend and share access to food and to support each other in coalitionary aggression. These alliances provide competitive advantages over males, who rarely form such alliances with each other. Unlike evidence in other species, cooperation among female bonobos is not readily explained by kinship, or by reciprocal altruism, which suggests that individuals cooperate selectively only with those who return the favor.
In addition to maintaining high levels of cooperation within their own community, encounters with other communities are frequently peaceful for females and often involve sharing of feeding trees and friendly interactions. This suggests that female bonobos may maintain a social network that extends beyond their immediate community. Such evidence is inconsistent with parochial altruism, which suggests that group-level cooperation in ancestral humans evolved as a strategy to win in conflicts with other groups. In humans and the closely related chimpanzee, the neuropeptide oxytocin is involved in cooperation within groups and competition between groups. Similarly, testosterone and cortisol mediate competition across species. However, preliminary results indicate different hormonal responses to competition in bonobos, likely reflecting differences in past selection pressures.
The goals of this research are to investigate the ecological and social benefits of cooperation within and between communities for bonobos, and their hormonal underpinnings, to better understand the evolutionary factors shaping cooperation that is largely led by and provides benefits for unrelated females. Field research will be conducted at LuiKotale, Salonga National Park, Democratic Republic of Congo, home to two habituated bonobo communities. We will collect behavioral data on social interactions and combine GPS data on movements with ecological data on food availability within and outside of core community home ranges, to measure ecological benefits of foraging in areas of home range overlap with other communities. We will collect urine samples non-invasively for hormone analyses. We will use social network analyses to test for alternatives to kin selection and reciprocal altruism to explain patterns of group-level cooperation among female bonobos. During encounters with different communities, we will test for sex-specific behavioral and physiological responses to potential competition. Results will highlight the advantages of building large-scale alliances within and between groups in a close phylogenetic relative of humans.