- Despite a decade of uncontrolled poaching, researchers have found what they describe as a “healthy” population of 200 chimpanzees in Côte d’Ivoire’s Comoé National Park.
- With the help of camera-trap footage, researchers found that the Comoé chimps display unique types of behaviors not found in other chimp populations in West Africa.
- Like elsewhere in West Africa, the chimps’ habitat remains under pressure from farming and herding.
Conservationists feared that chimpanzees in Comoé National Park might have been wiped out during a decade of civil conflict in Côte d’Ivoire. But camera-trap footage found a healthy population and has since documented unique behaviors not observed in other chimp populations in West Africa.
The western chimpanzees (Pan troglodytes verus) of Comoé National Park in northern Côte d’Ivoire have a unique way of drinking water during the dry season. They chew the ends of sticks to make a sort of brush and then dip the brush end of the stick into tree cavities where water has accumulated. Then they pull the stick out and suck on the end of the brush.
This type of behavior had been observed occasionally in other chimp populations before, but researchers were surprised by how common it was among Comoé chimps.
“We found that, well, apparently they don’t use the sticks because they are more efficient, but because they prefer them,” Juan Lapuente, head of the Comoé Chimpanzee Conservation Project, told Mongabay. “It is part of the culture. That’s the way they do it.”
Though cultural differences between chimpanzee social groups have been studied for decades, researchers still know very little about why some groups develop certain tool-use behaviors while others don’t, or how behaviors are passed from one group to another.
But recent studies suggest the environment chimps live in may play a role in what kinds of behaviors certain groups display. One study looked at the behaviors of 144 chimp groups and found that chimps in variable environments tend to develop a wider range of behaviors.
“Chimpanzees experiencing greater seasonality, living in savanna woodland habitats and located further away from historical Pleistocene forest refugia were more likely to have a larger set of behaviours present,” primatologist Ammie Kalan said in a post on the Max Planck Institute for Evolutionary Anthropology website.
The Comoé landscape is just such a mosaic of savanna and woodland, the kind of environment in which human ancestors were believed to have lived for more than 6 million years. Lapuente and other researchers say studying how chimps navigate this landscape could help us understand our own history. The way chimps adapt to their environment could give us hints about how our ancestors adapted millions of years ago.
The chimps of Comoé have adapted to survive in periods when access to water becomes more challenging. Lapuente and his team found that the sticks selected for water dipping tended to have longer and thicker brushes than sticks the chimps used for other behaviours, like honey dipping. Comoé chimps also chewed and folded leaves to make sponges that they would dip into water-filled cavities. When food becomes scarce, the chimps have been spotted peeling off the bark of kapok trees (Ceiba pentandra) to access the edible layer of cambium tissue beneath.
All of these tool-use behaviors were recorded on camera traps set out by Lapuente and his team. Camera-trap footage has also revealed other behaviors like stone throwing.
The return of research in Comoé
It’s only in the past decade or so that this type of research has been possible again in Comoé National Park. Following a disputed election, Côte d’Ivoire entered a period of civil war from 2002 to 2004, and then again from 2011 to 2012, though the years in between remained tense.
Civil conflicts in other countries have been devastating for some endangered animal populations as violence often allows poachers, sometimes including the warring factions themselves, easy access to wildlife while the patrolling of protected areas is more difficult. Surveys in Comoé in 2007, 2010 and 2012 hadn’t found much evidence of chimps in the park. So conservationists working in Comoé were concerned that chimp populations may have been wiped out.
“Between 2002 and 2011 there was this complete chaos,” Lapuente said. “There was no surveillance, nothing in the park. And there were poachers coming with trucks all the way from Nigeria. They took loads of meat and pieces. For instance, they wiped out the lions that were left because this was a huge market.”
It wasn’t just the lack of surveillance during the civil war that hurt chimp populations in Côte d’Ivoire, though. Loss of habitat and poaching were problems even before the conflict; between 1990 and 2007, the country lost 90% of its chimp population.
Since 1960, Côte d’Ivoire has lost around 90% of its forests. Many of the country’s forests have been cleared for cocoa plantations as Côte d’Ivoire has taken its place as the world’s largest cocoa producer. One study published in 2015 surveyed 23 protected areas in Côte d’Ivoire and found that more than half of those areas no longer had any chimp and other primate populations largely due to habitat destruction.
Roman Wittig, director of the Taï Chimpanzee Project, has observed the landscape around Taï National Park in the southwestern part of the country over decades. He first went to Taï in the late 1990s while doing his Ph.D. research. When he returned in 2011, the landscape had changed completely.
“It was shocking to see that the [agricultural] fields go to the park limit so there is no buffer zone at all anymore,” Wittig told Mongabay. “[Before] there would be forest even outside the actual national park.”
Wittig also saw a steep decline in the chimp population following his first visits. In the 1990s, estimates suggested there were more than 3,000 chimps in Taï National Park, but now there are around 400-1,000 left, he told Mongabay.
Hope for chimpanzees in Comoé
When Lapuente and his colleagues first began surveying Comoé in the years after the civil war, they didn’t know what to expect. But over the course of three years, starting in 2015, their surveys indicated there was a viable chimp population left. Since then, and with the help of camera traps, they’ve documented around 200 chimpanzees in and around the park. It’s likely the second-largest population of chimps in Côte d’Ivoire.
“Of course, there are less chimps in the park than there were 20 years ago,” Lapuente said. “[But] 200 chimpanzees is a very healthy population for nowadays’ standards.”
Lapuente’s assistants help set up the camera traps in the forest and keep the observations going when Lapuente travels. Though the technology has improved, it’s still grueling work. It can take more than a week to set up the camera traps, Harouna Dabila, one of the assistants, told Mongabay in French. Some days, they have to walk more than 30 kilometers (19 miles).
Lapuente said he hopes the presence of researchers acts as a deterrent to poachers in Comoé. He and his team are also working with local communities and involving them in conservation efforts.
Poaching isn’t his only concern, though. Lapuente said he fears there are increased pressures from people outside the park trying to make a living. Because cattle herders can’t graze on farmland in the park’s buffer area, they go for the forest instead.
“The chimps are finding their habitat shrinking at a terrible pace,” Lapuente said. “There are cattle herders entering there freely and they do burn the gallery forest to get fresh grass, it’s really destructive. The forest never comes back to normal.”
Western chimp numbers revised up to 53,000, but development threats loom
Banner image: The critically endangered western chimpanzee (Pan troglodytes verus). Image by Mario Plechaty via Adobe Stock.
Lapuente, J., Hicks, T. C., & Linsenmair, K. E. (2016). Fluid dipping technology of chimpanzees in Comoé National Park, Ivory Coast. American Journal of Primatology, 79(5), e22628. doi:10.1002/ajp.22628
Lapuente, J., Arandjelovic, M., Kühl, H. S., Dieguez, P., Boesch, C., & Linsenmair, K. E. (2020). Sustainable peeling of kapok tree (Ceiba pentandra) bark by the chimpanzees (Pan troglodytes verus) of Comoé National Park, Ivory Coast. International Journal of Primatology, 41(6), 962-988. doi:10.1007/s10764-020-00152-9
Kalan, A. K., Kulik, L., Arandjelovic, M., Boesch, C., Haas, F., Dieguez, P., … Kühl, H. S. (2020). Environmental variability supports chimpanzee behavioural diversity. Nature Communications, 11(1), 4451. doi:10.1038/s41467-020-18176-3
Lapuente, J., Ouattara, A., Köster, P. C., & Linsenmair, K. E. (2020). Status and distribution of Comoé chimpanzees: Combined use of transects and camera traps to quantify a low-density population in savanna-forest mosaic. Primates, 61(5), 647-659. doi:10.1007/s10329-020-00816-3
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