Hello to all you chimpanzee enthusiasts! We’re back with another article to talk to you about chimpanzees and their social lives! When it comes to the importance of sociality, chimpanzees are no less dependent on their friends as we are. That being said, there are some clear differences between humans and chimpanzees and the ways in which we live our social lives. Today’s article will look at those two sides of the coin in more detail.
For decades, scientists have debated on the subject of chimpanzee mental capabilities and to what extent they may possess theory of mind (Gallup, 1970). Theory of mind is an important social-cognitive skill that involves the ability to think about mental states, both of the self and of others. A recent study in the journal PNAS (Proceedings of the National Academy of Sciences) titled “Great apes use self-experience to anticipate an agent’s action in a false-belief test”(2019), is an important advance in efforts to determine to what extent our closest relatives can understand others’ perspectives. Indeed studying this topic in chimpanzees also helps to clarify which aspects of the human mind were already present 6-9 million years ago in our common ancestor and which evolved uniquely in the human lineage after the divergence from the other apes. There have been many such studies that have attempted to investigate similar topics, however all of these take place in captive settings where chimpanzees, though they may live long healthy lives, are ultimately not exposed to their natural, innate settings in which their brains and bodies were adapted for. Answering these questions in a natural setting is close to impossible because there are too many factors to control and the ethical questions that arise are numerous and indeed valid. In the wild however, over many decades of behavioral research, scientists have learnt much about our closest living relatives just by watching them go about their daily lives. We are constantly learning and discovering new information about the ways in which chimpanzee society functions and the way in which the chimpanzee mind works in their natural habitats. Chimpanzees are now well known for their cooperative skills, these are most notably observed in group hunting, territory defense and the formation of alliances (Boesch, 1994).
Another one of the many interesting topics of social cognition is social learning. Defined simply it is the ability to transfer information between individuals. In humans social learning has led to a diverse cultural world. Do you think our non-human primates have culture as well? This question has been a hot topic of debate for the past decades among primatologists, psychologists and anthropologists alike. The main findings are that even if not as starkly diverse as human culture, there are clear site-specific and even multi-generational “traditions” in chimpanzee populations. These cultural variations pertain to some of the first observations made by Jane Goodall herself. Some examples of current differences researchers have identified are: tool use, aimed throwing, nest building, grooming, rain dancing and courtship rituals. Differences can also mean a complete absence of a certain type of behavior amongst separate chimpanzee populations or even communities. One of the most interesting findings has been that chimpanzees belonging to one community sometimes develop different behavioral patterns from their neighboring communities even when they share the same habitat and have access to the exact same materials (Luncz et al., 2012). This in some cases could be due to “lessons” between mother and offspring, teaching the ways of the community. However chimpanzees learn all throughout their adolescence from all group members. To finish up the short briefing on chimpanzee culture we want to provide you with one more “hands-on” example. An interesting study studying one community of chimpanzees in the Kibale forest in Uganda showed that chimpanzees there use sticks to extract honey from a log whilst individuals in the Budongo forest of Uganda only 200km away use chewed up leaves as “sponge-like” tools to extract the sweet honey from logs (Brunette, 2020).
Chimpanzee Eating Tortoise (Site-Specific Behavior)
Now we will dive deeper into another aspect that is important and vital for social relationships to form and develop: Emotions. Emotions are said to be indicated via facial expressions (Ekman & Friesen, 1971). These expressions carry a variety of information about motivation and intention. In humans the study of and effort to make sense of these facial expressions has spanned decades (Ekman, 1997). Scientists have now even created a pretty impressive tool for facial coding for Chimpanzess called ChimpFACS, which can be used as a tool to help us understand them better. Identifying prototypical expressions can help propel the research of chimpanzee social cognition as it can provide a standard for scientific work (Parr et al., 1998). Nonetheless, there is still a major problem to get photographic data of emotional expressions as the situations they occur in are highly charged and involve fast movements. However despite these hurdles, research into emotions and social phenomena is producing interesting findings. For example, using these tools researchers have quantified chimpanzee empathy, showing that individuals look out for one another and provide help when needed. An example of this in a captive setting is at the Tchimpounga Chimpanzee Rehabilitation Centre where female chimps have been known to adopt orphaned infants. This also takes place in the wild, at Tai Chimpanzee Project in Cote d’Ivoire there is the amazing story of adult male Fredie and his band of orphans that he cared for and protected, most into adolescence. On a final note, it is important to note that chimpanzees who are deprived of social interactions or their normal living environment often succumb to depression and other negative emotional states. Though sanctuaries around the world do their best to create healthy living environments for chimpanzees, the best place for a chimp is in the wild where they belong.
Now that you know a bit about the mental and cultural capabilities of chimpanzees let’s take a look into social structure and the story behind hierarchies! Be warned the social structures of chimpanzees are not as simple as they appear and can sometimes even seem as interwoven as those in Game of Thrones (disclaimer: do not take this comparison too literal). Indeed the mixture of friends, foes, community and power dynamics at play make for a lot of interesting phenomena to study and understand.
Let's start at the top of the ladder - with the alpha-male. Becoming the alpha-male in a group does not come with a simple guaranteed approach, but rather it depends on the personality of the individual chimpanzee and the standing of that chimpanzee's mother throughout his life. However what most alpha-males do have in common is a strong coalition with other subordinate chimpanzees. These other individuals are vital in helping him both gain and then maintain the power he possesses. These allies can be playmates from juvenile years, brothers or even “new” friends looking to increase their standing in the group. Sometimes however there are new coalitions formed to overthrow an old leader. Much of a chimpanzee male’s life is dedicated to climbing up or being knocked down the chimpanzee social ladder (read about the ‘Fall of Ferdinand’ here). All in all it's an ever changing power struggle, and some of the most exciting moments to watch in chimpanzee society are when places on the hierarchy are challenged (Brittany Cohen-Brown, 2018).
Now what about female chimpanzees? How do they fit into the hierarchy? First of all, it's important to know that there is also an alpha-female. A major difference between male and female alphas is that females aren’t as likely to use aggression and violence to get to their goals. They rather prefer to use long-time relationships and personality traits to either maintain their place or gradually move up the hierarchy. However, this is not to say it's all calm and peaceful, female chimpanzees are capable of using their force, especially when displeased by lower-ranking females. One major benefit being the female alpha is that she is more likely to be more successful when it comes to reproduction and access to food. As mentioned before the offspring of higher-ranking females tend to achieve a higher status themselves than chimps born to lower-ranking mothers (Brittany Cohen-Brown, 2018).
Another interesting piece of information about chimpanzees is that they do not have nuclear families but are rather promiscuous. This comes with a certain advantage: Not being able to know who the father is. This reduces stress that females and their children are faced with and serves as an indirect protection for them. However in very rare cases in intra-community settings do male and sometimes even female chimpanzees kill the offspring of others, due to rivalry (males) or food competition (females). Another thing to note is that male chimpanzees stay in their natal community for their whole life, while females tend to leave and join other communities around puberty (de Waal, 2005).
As we are talking about males and females now let's quickly take a look at “parenting”. Firstly, it should not be understood in the same way that we humans see parenting. For the most part male chimpanzees are not involved in raising the offspring. This is due to the promiscuous dynamics in a community mentioned above. Yet, interestingly more recent studies that can identify paternity in the group show that some fathers seem to be able to identify their offspring and behave in a somewhat positively biased way towards them (Murray et al., 2016). However, the origins of that are not fully understood by research as of now. In general, mothers do all of the hard work! When it comes to mother-child relationships there are different degrees of parental care and mothering styles, comparable to us humans. Some mothers are very protective and others are more relaxed.
Mother and Child
With that all being said, let's take a look into one of the more sinister social aspects of chimpanzees by investigating a phenomenon that was once thought to be uniquely human – war. This phenomenon is common in all communities of chimpanzees that have neighbouring communities. There are several reasons that these aggressive interactions may occur or increase: territory defense, competition for food or territory, predation and more. One famous instance of this is the “Gombe War'' that waged for four years in the 1970’s. It commenced with the death of the original alpha-male which then split the community into two groups the “North” and the “South”. The larger of these two groups then began to invade the territory of the others - if and when they found a rival they attacked him and left him to die of his wounds. Ultimately, this led to the annihilation of the entire group.
Even rarer than this is interspecies violence. Here at Loango the first two observations of two separate encounters between chimpanzees and gorillas were made in 2019. In both situations the chimpanzees outnumbered the gorillas and instigated the attacks. The result: two infant gorillas were killed. What caused this outburst of violence against the gorillas? We assume that it might be due to interspecific competition, or the possibility that the infant gorillas were seen as prey or even that the chimpanzees saw the gorillas as intruders much in the way they view neighbouring chimpanzee groups. If you are interested in more information on that feel free to take a look at our publication in Nature: https://www.nature.com/articles/s41598-021-93829-x
We hope that all this information gives you a rough idea of how interesting and complex research into chimpanzees and their social structures is and how surprising some observations can be. Also, there is much uncharted territory still left to explore!
Thats all we have for you today. Stay tuned for upcoming articles!
Best wishes
The Ozouga-Blogging-Team
References:
Gallup, G. G., Jr. Chimpanzees: Self-recognition. Science 167, 86-87 (1970)
Kano, F., Krupenye, C., Hirata, S., Tomonaga, M., & Call, J. (2019). Great apes use self-experience to anticipate an agent's action in a false-belief test. Proceedings of the National Academy of Sciences of the United States of America, 116(42), 20904-20909. https://doi.org/10.1073/pnas.1910095116
Boesch, C. Cooperative hunting in wild chimpanzees. Animal Behavior 48, 653-667 (1994).
Luncz, L., Mundry, R., & Boesch, C. (2012). Evidence for Cultural Differences between Neighboring Chimpanzee Communities. Current Biology, 22(10), 922-926. doi: 10.1016/j.cub.2012.03.031
Matt Brunette, JGI Canada Volunteer (2020, June 9). Do Chimpanzees Have Culture? Jane Goodall. https://janegoodall.ca/our-stories/chimpanzees-and-culture/
Ekman, P., & Friesen, W. V. (1971). Constants across cultures in the face and emotion. Journal of Personality and Social Psychology, 17(2), 124–129. https://doi.org/10.1037/h0030377
Ekman P. Should we call it expression or communication?. Innovations in Social Science Research, 1997, vol. 10 (pg. 333-44)
Parr LA, Hopkins WD, de Waal FBM. The perception of facial expressions in chimpanzees (Pan troglodytes), Evolution of Communication, 1998, vol. 2 (pg. 1-23)
Cohen-Brown, B. (2018, July 11). From Top to Bottom, Chimpanzee Social Hierarchy is Amazing! Jane Goodall’s Good for All News. https://news.janegoodall.org/2018/07/10/top-bottom-chimpanzee-social-hierarchy-amazing/
de Waal, F. A century of getting to know the chimpanzee. Nature 437, 56–59 (2005). https://doi.org/10.1038/nature03999
Murray Carson M., Stanton Margaret A., Lonsdorf Elizabeth V., Wroblewski Emily E. and Pusey Anne E. 2016 Chimpanzee fathers bias their behaviour towards their offspring, R. Soc. open sci.3160441160441