HOPE report

Number: 25-004

Accomplishing the field work for my PhD about the relationship between social hierarchy and personality in wild-living bonobos

Report: GARAI Cintia Judit

Date: 2013/5/4 - 2013/11/18

Hierarchy in the bonobo society is a hotly debated issue. Unlike other great apes, bonobo females are in almost equal, or even higher, social status with males, and interventions by high-ranking mothers largely contribute to acquisition of high ranks by their adult sons. Such a strong influence of females in patrilineal society is one of the important similarities between bonobos and humans.

The hierarchy in the bonobo society has been studied based on gender, life history and age, but its relatedness to personality has never been examined. However, at this high level of intelligence, personality cannot be excluded as having important roles in behavior. My study examines the correlation between personality and the hierarchical rank in wild-living bonobos. The results will contribute to our understanding of unrevealed aspects of bonobo society, in special regard to the contribution of personality to high positions of females in hierarchy. It will also lead us to uncover certain connections in the evolution of female social status between bonobos and humans.

Bonobos are endemic to the Democratic Republic of Congo, and the number of places where they can be studied in the wild is very limited. Wamba, the Japanese field site to study bonobos is the oldest site among all. It was established in 1973, exactly 40 years ago. As a consequence, local assistents know the individuals very well, which is a great help for my research topic.


In order to examine the personality traits, I applied focal animal behavioral observation. I collected 20 hours of 16 individuals that I included in my study, i. e. 320 hours in total. For learning the hierarchy I recorded aggressive interactions ad libitum. All sexual and social interactions were noted as well.

Preceding studies have revealed several candidate genes that may influence personality traits in humans, chimpanzees and gorillas, but this has not yet been studied in bonobos. In order to analyze personality related genes in this species, I collected fecal samples from focal individuals.

I intend to examine the level of cortisol that may be related to personality and hierarchical positions. For this purpose I collected urine samples from the focal individuals.

I asked local trackers to fill out a questionnaire on personality of my focal bonobos. During the next months I plan to analyze all these data for my PhD.

Ikura playing face


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