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In the fascinating world of bonobos, the social dynamics between males and females are notably distinct. Female bonobos wield considerable influence over mating choices, having the autonomy to decide when and with whom to engage. They deftly deflect unwanted advances from males, who are aware that coercion is not an option. Furthermore, when it comes to food resources, it is primarily the females who regulate access to valuable items, like a fresh kill, as they eat on the ground while males wait in the trees for their turn.
This dynamic might seem unremarkable from a human perspective, but as Martin Surbeck from Harvard University observes, it is quite unusual for an animal such as a bonobo. Typically, in species where males are larger and stronger, one would expect a male-dominated social order. However, bonobo females consistently enjoy a higher status than their male counterparts. The question of how this atypical structure arises has puzzled researchers until now.
“There were various theories proposed,” says Barbara Fruth from MPI-AB, who has led research on bonobos at the LuiKotale research station for three decades, “but none had been validated through observation of wild bonobos in their natural environments.”
Female solidarity as a tool for power
New research by Surbeck and Fruth has shed light on this intriguing phenomenon, presenting the first empirical evidence from wild bonobo populations that explains how females assert power: through the formation of alliances. Their study reveals that when females come together in groups, which they refer to as “coalitions,” they tend to outrank males. Notably, females in 85% of observed coalitions actively targeted males, effectively coercing them into submissive positions and influencing the hierarchy within their groups.
“This evidence suggests that female solidarity can reverse the male-biased power dynamics often seen in mammalian societies,” Surbeck states, highlighting the significance of female support in ascending social rankings.
A window to wild bonobos
To conduct their research, an international team analyzed three decades of data from six distinct bonobo communities situated across various locations in the Democratic Republic of the Congo, the sole habitat of wild bonobos. Their dataset, including observations of 1,786 male-female conflicts, was pivotal in understanding the circumstances contributing to “female power.” The research indicated that factors such as physical strength, social backing, and the possession of desirable resources all influenced the outcomes of these conflicts. Surbeck explains, “You can emerge victorious from a conflict by being stronger, having allies, or possessing something that others want but cannot seize by force.”
The researchers had hypotheses about the potential drivers of female dominance, including reproductive strategies like concealed ovulation, which might prevent males from monopolizing mating opportunities. However, the pronounced impact of coalition formation was unexpected, as the adult females involved were unrelated individuals from different groups, revealing surprising levels of cooperation. As Surbeck notes, “It’s uncommon to see such coalitions develop in nature.”
When these coalitions do form, their presence is unmistakable. The initial sign is a loud chorus of vocalizations that can be overwhelming, leading Fruth to remark, “You have to cover your ears.” The conditions that trigger these coalitions are often sudden and unpredictable, such as when a male poses a threat to a juvenile. In response, females will aggressively pursue the male offender, sometimes resulting in severe repercussions. “Their aggressive assertion of power is quite effective,” states Fruth, reflecting on the reluctance of males to overstep boundaries.
Not always “dominance”
However, this extensive study, which involved examining six bonobo communities, revealed complexities within the female dominance narrative. While females triumphed in 61% of conflicts and generally outranked 70% of males, Fruth emphasizes that this dominance was not absolute. “It’s more precise to say that female bonobos hold high status rather than enjoy unchallenged dominance,” she explains, highlighting variability across different populations.
The authors suggest that female coalitions are just one means through which empowerment occurs. The autonomy of females in reproductive matters likely plays a significant role in shaping intersexual power relations. The uncertainty surrounding female fertility prompts males to adopt a more non-confrontational approach, focusing instead on remaining close to females rather than attempting forceful coercion. Future research will delve deeper into these dynamics and explore other potential influences.
The inquiry into the social structures of bonobos raises deeper questions about the nature of their alliances, and while answers may remain elusive, Fruth expresses a sense of optimism: “The fact that bonobos, our closest living relatives, formed alliances among females presents a hopeful perspective on female empowerment alongside males in our evolutionary journey.”
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