Listen to the soundscape of Western Tanzania
From the field!
By Gal Badihi
Hi reader! I am a PhD student from the University of St Andrews (Scotland). I study how the social and ecological environment of East African chimpanzees influences the way individuals use gestures to communicate during daily social interactions. Before coming to GMERC my research focused on another E African chimpanzee community: the amazing Waibira community in Uganda. I came to GMERC for two months in the summer of 2021 to learn how Issa chimpanzees use gestures and to compare their gesture use to that of other communities.
My data collection methods involve following a group of chimpanzees and capturing videos of gestural interactions. I try to focus on individuals who are involved in behaviour that requires more communication (like grooming or aggression), or central individuals in the group (like the alpha male), which are more likely to interact with others. To optimize my data collection, I must pay careful attention to the different relationships within the community and to individual behavioural differences.
Now, sitting in my government mandated quarantine in cloudy Scotland, I have some time to reflect on my experience in Issa. While I expected to find some differences between Issa and Waibira communities, I soon realised that, although they all belonged to the same subspecies, the Waibira and Issa chimpanzees are very different in their behaviour (for example, I observed fewer aggressive interactions between males in the Issa compared to Waibira, but I observed more clear cases of cooperation between Waibira males compared to Issa). During my first weeks at Issa, it became clear to me that I could not extrapolate my experiences of the Waibira community to Issa. I was especially struck by the new kinds of relationships I observed in Issa and two subadult females which engaged in many interesting interactions with other individuals.
The subadults in question are Kasolya and Corona. They are likely of similar age and are frequently in oestrus (sexually receptive to males). While they should be competitors in this situation – competing over sexual partners – their relationship rarely involved any agonistic behaviour. In fact, they often groom together and engage in other affiliative behaviour.
Interestingly, they also appear to hold different roles within their relationship, with Kasolya often providing support for Corona during times of stress. One day, Kasolya and Corona were sitting on the same branch in a tree, when a few males started to display – shaking branches, hitting the tree trunk, jumping from branch to branch, and vocalising loudly. Displays increase the level of arousal in a group and Corona and Kasolya were no exception. Both females were on edge and Kasolya’s hair was piloerect (standing upright). And as Kasolya moved a little further down the branch toward Corona, Corona presented her genital swelling to Kasolya, who then proceeded to mount Corona from behind, giving her a small embrace. This gesture is often seen as a sign of support or reassurance and is also observed between males from the same community during stressful situations like intercommunity encounters.
While Kasolya and Corona clearly hold important social roles in each-others’ lives, they also play a key part in the daily lives of the infants in the community. Both females often seem to take on the role of ‘babysitters’ – playing with, grooming, and sometimes carrying the infants of other females. However, they do this in slightly different ways…
Kasolya often appears to dictate the rules of play, for example, chasing away an older juvenile, when she wants to play alone with an infant or putting her foot down and flinging her arm at the infants when play time is over. But, when she is with an infant she takes great care to watch them. One day I saw Kasolya diligently grooming Kinundi (a young infant) for over an hour while Kinundi’s mother (Kinanda) was feeding on another branch. When time came to leave the tree, Kasolya carefully accompanied Kinundi to his mother across the tree who then carried him down.
Corona is less likely to refuse play invitations, and the infants often solicit her, especially Joto, another infant. Even if Corona is grooming another individual, Joto has no problem climbing on her and playfully starting a biting match. In these situations, Corona either continues grooming with one hand while allowing Joto to use the other as a chew toy or stops grooming to give Joto her full attention. One time, I saw Joto kick Corona as she was climbing down a branch with her mother Jua. Corona gently moved out of the way, and even waited for Joto on another branch where she and Joto embraced before moving on!
While I can only speculate as to the reasons behind Kasolya’s and Corona’s relationships with the infants, seeing the level of trust mothers put in these two young females is incredible. Kasolya and Corona seem to take their babysitting roles very seriously, and I am excited to see how their roles within the community will change when they have their own infants.
In the two months I spent with the Issa chimpanzee community I was exposed to only a brief snapshot of their lives and relationships. I chose to focus on Kasolya and Corona for this blog because their behaviour surprised me. Much of the published work on East African chimpanzee sociality suggests females are generally asocial, low-ranking individuals that hold minor roles within the community and often spend a lot of time alone or trying to find males that will copulate with them. Kasolya and Corona’s relationship, along with their hyper-sociality was not what I expected. It confirmed my suspicion of just how different chimpanzee communities can be from each other and the importance of studying behavioural diversity to gain a fuller picture of what chimpanzees are really like.
Thank you, Corona and Kasolya, for letting me observe your beautiful relationship and learn from you!