- A recent study using camera traps and direct observation documented well-digging behavior in a group of chimpanzees in Uganda, initiated by a female that had immigrated into the group.
- Researchers were surprised to observe this behavior in this rainforest-dwelling population as water tends to be easily accessible in this habitat.
- The findings suggest this learned behavior may be helpful for the conservation of this group, as the chimps have picked up an adaptive measure that could help them survive a drought.
There are moments in researchers’ lives when they realize the significance of something they hadn’t paid much thought to in the past. For primatologist Catherine Hobaiter and her team, one such moment came when they watched a subadult female chimpanzee (Pan troglodytes schweinfurthii) they call Onyofi digging in the mud of her rainforest habitat in western Uganda. Hobaiter, who works at the University of St. Andrews in the U.K., says she initially thought Onyofi was digging for roots. But then she saw that Onyofi was peering into the hole she had just made.
“She was clearly kind of waiting afterwards,” Hobaiter says. “And the other part that sort of drew my attention to it was that there were other chimps around and they seemed fascinated by her behavior. And you don’t get that so often.”
Hobaiter watched as the hole began to fill with water and Onyofi drank from it. She had noticed these holes in the ground before but never imagined that these were chimp-made wells.
Previous examples of chimps digging wells have been observed in areas where water is a limited resource, like in a savanna. Onyofi’s well digging was the first time this behavior was observed in rainforest-dwelling chimps. Researchers suspect the behavior was picked up by many chimps because they also face some water shortages, mostly during the dry season when their seasonal river dries into a muddy pool. And Onyofi may have brought this behavior to the group.
Onyofi is an immigrant female who joined the Waibira chimpanzee community of 120 individuals in Uganda’s Budongo Forest in 2014. Since 2011, researchers have been habituating the group to the presence of humans for research. It wasn’t until 2017 that they spotted them digging wells, though.
The recent findings, published in the journal Primates, may support the hypothesis that new behaviors picked up by chimpanzee groups are often introduced by females that come in from other communities.
“It is very rare to know the origin of cultural behavior [in chimps],” says primatologist Tetsuro Matsuzawa, a visitor in psychology at the California Institute of Technology.
Matsuzawa, who was not affiliated with the well-digging study, has researched chimpanzees in the wild and in captivity for decades. He says the hypothesis that immigrant female chimps help spread new behaviors is becoming more widely accepted among primatologists. And the Waibira community isn’t the only example. In a study of chimps in Guinea, West Africa, Matsuzawa and his team ran a nut-cracking experiment, introducing unfamiliar nuts to a group of chimpanzees. One immigrant female showed no hesitancy in cracking open the new nut, suggesting she might have been familiar with the nut when living with her birth community.
The study in Waibira, which was able to trace different chimps learning the well-digging behavior over time, can help fill in gaps in understanding about how chimps learn.
“Previous studies have revealed that chimpanzees have a cultural tradition unique to each community,” Matsuzawa says. “The present study clearly showed the origin of the cultural behavior of digging wells to get water.”
To Hobaiter, the study highlights the significance of studying female chimps, who have historically received less attention than males, which tend to become habituated to humans faster and are less shy.
“It’s been biased towards studying males for a very long time,” Hobaiter says. “I think the opportunity now [is] to really study female chimpanzees: the fact that they move between groups and have this potential for different sets of cultural knowledge; the fact that they are the ones who are then perhaps shaping the kind of social associations within the group in different ways. I think there’s an awful lot that we can look into.”
In total, between 2013 and 2019, researchers documented 56 instances that were considered “well-digging events” by 20 different chimps of the Waibira community. Most of the well digging observed was done by female chimpanzees. And Onyofi was the most prolific well digger in the group, with 14 wells documented between 2015 and 2019.
Onyofi’s regular well digging and the fact that researchers found footage of her doing it back in 2015 — two years before the first direct observation — indicate there’s a good chance that Onyofi was the first one to do it before others started copying it. The researchers found multiple instances of other chimps peering at Onyofi and even drinking out of the wells that she and other chimps would make.
The study also considered the possibility that digging wells presents a cognitive challenge for chimpanzees. Because water doesn’t fill up in the hole right away, it’s possible that some chimpanzees don’t see the link between digging and accessing clean water. This could also explain why only 20 of the 120 chimpanzees in the community appeared to pick up the behavior.
Still, being able to observe 20 individuals digging wells was a significant enough sign that the behavior was habitual — especially since both males and females were observed doing it.
“To be honest we are extremely happy with the 20,” says Hella Péter, a co-author of the study and Ph.D. student at the School of Anthropology and Conservation at the University of Kent, U.K. “Chimpanzees are extremely conservative and they are super, super picky in what they seem to learn.
For Péter, 20 chimps learning to dig wells in just seven years is impressive. And this new behavior may also help in the conservation and long-term survival of the group.
“Even though they currently do not have to deal with droughts, if droughts hit them, which is a possible scenario, they likely have at least one coping mechanism,” Péter says.
She and her team expect well digging to become even more common in the Waibira community in the coming years. They plan to continue monitor the chimps with the help of the Budongo Conservation Field Station’s long-term field staff, who often carry out the camera-trap deployment and observation work.
Banner image: A chimpanzee digs a well as another adult chimpanzee with an infant watches. Image courtesy of Hella Péter and the Budongo Conservation Field Station.
Citations:
Péter, H., Zuberbühler, K., & Hobaiter, C. (2022). Well-digging in a community of forest-living wild East African chimpanzees (Pan troglodytes schweinfurthii). Primates, 63(4), 355-364. doi:10.1007/s10329-022-00992-4
McGrew, W. C., Marchant, L. F., Payne, C. L. R., Webster, T. H., & Hunt, K. D. (2013). Well digging by Semliki chimpanzees: New data on laterality and possible significance of hydrology. Pan Africa News, 20(1), 5-8. doi:10.5134/177625
Biro, D., Inoue-Nakamura, N., Tonooka, R., Yamakoshi, G., Sousa, C., & Matsuzawa, T. (2003). Cultural innovation and transmission of tool use in wild chimpanzees: Evidence from field experiments. Animal Cognition, 6(4), 213-223. doi:10.1007/s10071-003-0183-x
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