Western Chimpanzees Have Declined By 80 Percent Over The Past 25 Years

The largest population of these animals—the only critically endangered chimp subspecies—sits in a region riddled with bauxite mines

A juvenile Western chimpanzee in the Bossou Forest of Mont Nimba, Guinea. Nature Picture Library / Alamy

Rebecca Kormos’ first experience seeing a wild chimpanzee changed her life. It was 1990, and the now-visiting biologist at the University of California at Berkeley was tracking western chimpanzees throughout Africa. Kormos had long been fascinated by the creatures that seemed so similar to humans, but different; for her, seeing them in their natural habitat was almost like going to another planet.

“Meeting a creature that was so like me, yet so adapted to living in the wild, shifted my perception of where I fit in the world,” she says.

Today, more than 25 years after that first encounter, a region in Guinea where Kormos also did research is one of the last strongholds of the critically endangered animals. Though it was considered marginal chimpanzee habitat when Kormos was there, it is one of the creature’s last stands: A study Kormos recently coauthored in The American Journal of Primatology shows the population of western chimpanzees dropped by more than 80 percent from 1990 to 2014.

“All chimp populations are plummeting,” says Kormos, who is also a member of the IUCN Primate Specialist Group's section on great apes. “They are an extremely adaptive population, they can live in marginal habitat. But they breed very very slowly”—which means populations take a longer time to rebound.

Western chimpanzees are one of four subspecies of chimps spread across Africa. They live in West Africa from Senegal down to Ghana, with the largest populations living in Guinea and the Ivory Coast. Unlike their near cousins, they play in water, live in caves and sometimes use spears to hunt other primate species. All chimpanzees are considered endangered by the International Union for Conservation of Nature, but western chimpanzees are the only subspecies considered critically endangered—and current populations face a number of threats.

The new study boasts data collected over years of research and taken from dozens of researchers, led by primatologist Hjalmar Kühl from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Chimpanzees are fairly nomadic, making new nests every night as they move through their territory. Researchers assessed the density of the primates by walking in straight lines through habitat in the handful of countries where western chimps are found—Senegal, Guinea, Ivory Coast, Ghana, Liberia, Guinea-Bissau, Mali and Sierra Leone—and counting the amount of chimp nests they encountered.

By adding these population studies to a central database, researchers found that only about 35,000 western chimpanzees remain in the wild.

Western Chimpanzees Have Declined By 80 Percent Over The Past 25 Years
Community representatives working for chimpanzee conservation in the Fouta Djallon region. Rebecca Kormos

Of these, roughly half are in the Fouta Djallon region in Guinea, where Kormos spent 18 months researching the animals from 1995 to 1997. During this time, she conducted population surveys and asked local people about their attitudes towards chimps. The estimations eventually contributed to the earlier numbers of chimps represented in the recent study.

Kormos found that people in the region had a surprising tolerance towards the animals, even on the rare occasions that chimps would kill a village goat for a meal. “There was an incredible interrelationship between the chimps and the people,” Kormos says.

The relationship likely has its roots in a Muslim taboo on eating primates. The area is primarily Muslim; most of the people Kormos interviewed were Fulani, a group of mostly Muslim people scattered throughout West Africa. But it could also stem from local legend. Kormos says some Fulani in the area believe that chimpanzees used to live in the villages, but they upset the gods. “They were sent to the forest and they were turned into chimpanzees as their punishment,” she says, adding that since the locals view the chimpanzees as ancestors, there is a taboo against hunting and eating them.

But a couple of decades have brought noticeable changes to the area. Kormos visited the Fouta Djallon area in September in work with the COMBO Project to help develop a national action plans for chimpanzees in Guinea, an effort by several conservation groups to reconcile economic development with conservation of biodiversity and ecosystem services in Africa. While she was there, she noticed that the chimpanzees were noticeably more skittish around humans.

“When they became aware of us they were alarmed and ran off,” she says. “They were a lot more scared than they used to be.” Kormos attributes this change to increased hunting pressure: While the Fulani themselves don’t generally poach the animals, chimpanzees in the area aren’t immune to outsiders coming in.

Biologists never predicted such high levels of chimps would live in the highland, area since the ecosystem is so different from the heavily forested areas where they are normally thought to live. But Kormos says that the high tolerance the Fulani have with chimps means the region has become something of a safe haven for the primates.

Not all parts of Guinea are like the Fouta Djallon in this respect. Kathelijne Koops, a post-doctoral researcher in the Department of Anthropology who studies chimpanzees’ technology use at the University of Zurich, says that the chimps in the area that she works in closer to the border of Ivory Coast and Liberia face large threats from mining. “It’s not like their situation is stable,” Koops points out. “Many of chimpanzee populations that are still there at the moment are threatened by mining concessions that are already given out.”

Koops worked on the research for the IUCN that eventually resulted in the changing of the conservation status of western chimpanzees from endangered to critically endangered in March last year. This listing changing, as well as Kormos’ study, provides the ammunition needed to increase conservation planning as countries like Guinea have officially endorsed IUCN statutes.

Stacy Lindshield, an assistant professor of anthropology at Purdue University, says that a similar taboo on hunting chimpanzees exists in parts of Senegal. There, however, a better understanding of the population recently has led to an expansion of the known range of western chimpanzees—“A little bit of good news in light of a lot of bad and depressing news,” as she puts it.

She says that the recent study was a well-conducted effort to document the decline of such a wide-ranging species, even if there are some gaps in the information (in southeastern Senegal, for example, she doubts populations have dropped by 80 percent). Koops agrees, saying, “It’s an approximation so you won’t be sure about the exact number of chimpanzees but it gives us an idea of the trend, whether they are increasing or decreasing.”

In Senegal populations suffer from an expansion of gold mining, which contributes to mercury contamination. Urbanization and infrastructure development also diminish chimp habitat, while climate change is making some savanna areas uninhabitable for chimps due to increasingly dry and hot weather.

Kormos says that the plummet in western chimpanzees across their range also includes poaching, dams and diseases. Even the Fouta Djallon has mining issues, as the region is rich in bauxite, and the looming threat of a possible hydroelectric dam project which would destroy a large swath of habitat. Kormos has worked with mining companies in an effort to get them to develop offset plants to compensate for the ecological damage of their projects.

But some positive signs exist, she says. Some nonprofits are working with the government of Guinea to create the Moyen-Bafing National Park area of the Fouta Djallon that holds an estimated 5,500 western chimps.

While the regions where western chimps make their homes may be far flung, Lindshield points out that everything is connected. The expansion of plantations for palm oil has led to a lot of habitat destruction, she says, but if consumers buy fewer of the common products with the oil, it could help the situation. Ecotourism could also bring some revenue to remote regions like the Fouta Djallon, which Kormos says would give locals more impetus to protect chimps.

Overall, however, conserving western chimpanzees will take commitment from local populations, national governments and the international community.

“West Africa has been exploited for her ivory, diamonds, rubber, cocoa, coffee, and now palm oil, bauxite, and iron ore too. The international community needs to commit to higher environmental standards for companies working in these countries and to compensate for any negative impacts they may have. Without this kind of commitment, the western chimpanzee could well be the first subspecies of our closets living relatives to go extinct.”

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