Chimps 90 Percent Gone in a "Final Stronghold"

Rebecca Carroll
for National Geographic News

October 13, 2008

West African chimpanzees have declined by 90 percent in the last 18 years in an African country that is one of the subspecies' "final strongholds," a new study stays.

Scientists counting the rare chimps in Côte d'Ivoire (Ivory Coast) found only about 800 to 1,200 of the apes—down from about 8,000 to 12,000 in 1989-90. Before the new survey, the country had been thought to harbor about half of all West African chimps.

"We were not expecting such a drastic decrease," said lead author Geneviève Campbell, a doctoral candidate at the Max Planck Institute for Evolutionary Anthropology in Germany.

The 1989-90 survey had itself represented a significant decline from 1960s estimates of about a hundred thousand West African Chimps in Côte d'Ivoire.

(See also: "Extinction Threatens Half of Primate Types, Study Says" [August 5, 2008].)

Nowhere to Run

Since 1990 Côte d'Ivoire's human population has grown by about 50 percent. This growth is the most likely cause of the decline in the chimp numbers, according to the report.

More people has led to more hunting and deforestation—key chimp threats—particularly since 2002, when a coup attempt sparked civil unrest that continues today, the study says.

One of the country's sanctuaries, Marahoué National Park, has lost 93 percent of its forest cover in the last six years, the new survey found.

Campbell said that at many of the sites her team visited, "the habitat is gone, and all the protected areas have been invaded by people."

The human "invasion" has left wide swaths inhospitable to other forms of life, she suggests.

At many of the survey sites, "it's not just the chimps—[there's] no animal at all," said Campbell, speaking by phone from Côte d'Ivoire.

In Decline Elsewhere?

A similar decline may have taken place in other countries within the West African chimpanzee range, says the new report, which was published today in the journal Conservation Biology.

The largest remaining population of the subspecies is believed to be in Guinea. But that belief is based on counts that are more than a decade old, according to the study.

In the falling West African chimp numbers, scientists see a door closing on their ability to understand and protect the subspecies.

"We know very little, really, about West African chimps compared to our knowledge of the East African chimp species," said Jill Pruetz of Iowa State University via email.

"Populations in Ivory Coast seemed to me the one place (and, perhaps Guinea) where we could still look," added Pruetz. The biological anthropologist, who was not involved in the study, is a National Geographic Society emerging explorer. (The National Geographic Society owns National Geographic News.)

Ape expert Frans de Waal of Emory University in Georgia described the report as "depressing."

"This study focuses on one rare subspecies of chimpanzee, but the same poor prospects hold for apes in general," said de Waal, who was not involved in the new research.

De Waal fears the report is "one of many to come."

Conservation Works

During the recent study, in all but 3 of the 11 survey sites, researchers found significantly fewer chimp nests—platforms built of branches high in the trees—than had been found in 1989-90.

In Marahoué National Park, study co-author Campbell found only one nest, versus 234 in 1989-90.

Two of the sites where West African chimps have not declined had only a few to begin with.

The third site is Taï National Park, a UNESCO World Heritage site that has benefited from intensive research and conservation efforts, according to the report.

The Taï numbers suggest that the apes' numbers respond to stable conservation efforts, according to scientists involved with the research.

"We urgently need to locate the viable population of western chimpanzees" in order to protect them, Campbell said.

Emory University's de Waal said preventing illegal hunting would be key.

"Unless we can put a stop to poaching—not just forbidding it but actually monitoring and stopping it—these trends may continue," he said.