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In a last 'stronghold' for endangered chimpanzees, survey finds drastic decline

October 14, 2008

In a population survey of West African chimpanzees living in Côte d'Ivoire, researchers estimate that this endangered subspecies has dropped in numbers by a whopping 90 percent since the last survey was conducted 18 years ago. The few remaining chimpanzees are now highly fragmented, with only one viable population living in Taï National Park, according to a report in the October 14th issue of Current Biology, a Cell Press publication.

This alarming decline in a country that had been considered one of the final strongholds for West African chimps suggests that their status should be raised to critically endangered, said Geneviève Campbell of the Max Planck Institute for Evolutionary Anthropology.

The booming human population in Côte d'Ivoire is probably responsible for the chimpanzees' demise.

"The human population in Cote d'Ivoire has increased nearly 50 percent over the last 18 years," said Christophe Boesch, also of the Max Planck Institute for Evolutionary Anthropology. "Since most threats to chimpanzee populations are derived from human activities such as hunting and deforestation, this has contributed to the dramatic decline in chimpanzee populations. Furthermore, the situation has deteriorated even more with the start of the civil war in 2002, since all surveillance ceased in the protected areas."

In the 1960s, the population of chimpanzees in Côte d'Ivoire was estimated at about 100,000 individuals. At the end of the 1980s, when the first and last nationwide chimpanzee survey was carried out, the total population of chimpanzees was estimated at 8,000 to 12,000 individuals. While that already represented a drastic decrease from the expected numbers, it nonetheless meant that Côte d'Ivoire harbored about half of the world's remaining West African chimpanzee populations.

In the new study, Campbell and Boesch's team conducted another nationwide survey, revealing a 90 percent drop in the chimpanzee nest encounter rate since the time of the last survey. That catastrophic decline in chimpanzees is especially strong in forest areas with low protection status, where the researchers saw no sign of the chimps. Even in protected areas like Marahoué National Park, chimpanzees have clearly suffered since surveillance and external funding support were disrupted by civil unrest in 2002.

"Following my transect lines in Marahoué National Park was similar to doing so in classified forests throughout the country, where I had to search long and hard to find any wild trees," Campbell said. "It was saddening that I only found one nest in this park, as during the previous survey they found 234 nests along the same transects. The one nest I did find was also in an area that had just been cleared for agriculture."

The only remaining refuge for the dwindling West African chimpanzees is Taï National Park. However, this population is also extremely threatened by poaching activities, Boesch said. External financial support in that park is scheduled to end in 2010, a move that will probably have disastrous consequences for the last vestiges of chimpanzees in Côte d'Ivoire.

"The comparisons between the results within national parks in Côte d'Ivoire and compared with the classified forest sends a very clear message: populations of wild chimpanzees living in protected areas with constant funding for conservation activities can survive even during period of rapid increase in human populations and political unrest," Boesch said. "We must appeal to the international conservation community to invest in sustainable funding of conservation activities in national parks with known importance for chimpanzee populations. Our results show that this works."

Cell Press