Thomas Breuer ©WCS-Max Planck Institute for Evolutionary Anthropology

More than 125,000 western lowland gorillas (Gorilla gorilla gorilla) have been discovered deep in the isolated forests of the Republic of Congo. This new find is a huge boost to their population, at least doubling estimates to between 175,000 and 225,000.

The gorillas were found during the first wildlife census of the area carried out by the New York-based Wildlife Conservation Society and the Government of Republic of Congo. Across an area covering 18,000 square miles, researchers tracked the animals by counting their nests, which nomadic gorillas build each evening to sleep in before rising the next morning in search of browse and a new overnight campsite.

Western lowland gorillas are one of four gorilla sub-species, which also include mountain gorillas, eastern lowland gorillas, and cross river gorillas. All are labelled endangered or critically endangered by the International Union for Conservation of Nature, with numbers of western lowland gorillas previously believed to be around 50,000 due to deforestation, warfare, poachers and the Ebola virus.

Emma Stokes, a WCS biologist who helped co-ordinate the study, said the dense forests in the Congo had kept the animals out of human sight. "It was an incredible moment when we realised the figures we were getting in. They had not been previously recorded because these are remote areas, inaccessible and tough to survey." The swampy forest terrain is also one of the main reasons the gorillas have been thriving as it is so inaccessible to humans. Since there aren’t any logging operations in the heart of these northern forests roads are all but nonexistent. That, in turn, has led to low levels of poaching or subsistence hunting. However, in recent years, the Republic of Congo has begun to sell the right to log the forests so things may change rapidly. Steven Sanderson, president of WCS says that the Congo government has committed to creating a new national park in this area but time is of the essence to ensure that this becomes a reality so that the area is protected before the hunters and loggers get there first.

Harvard University’s Richard Wrangham says loss of habitat is the greatest threat to the survival of the primates: "That’s partly from people just cutting down forest in order to be able to plant their crops but a lot of it is coming from big monocultures, a lot of it from logging, a lot of it from mining, so a lot of it from industrial actions as well.” Wrangham adds that forest clearance for growing crops for biofuels is going to intensify the loss of land for the primates. And while we may be able to try and control the actions of humans, one thing we can’t control is the threat from Ebola virus. “We must not become complacent. Ebola can wipe out thousands in a short time," says Stokes. Given the very high density of the animals found in this new group, they may be especially vulnerable if the virus did penetrate the group as recent research has shown that death rate is highest in gorillas living in groups (Caillaud et al., 2006).

Nevertheless, this is a huge boost for gorilla conservation and must be celebrated. As Craig Stanford, professor of anthropology and biology at the University of Southern California, says, "If these census results are confirmed, they are incredibly exciting, the kind of good news we rarely find."

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Caillaud, D.; Levréro, F.; Cristescu, R.; Gatti, S.; Dewas, M.; Douadi, M.; Gautier-Hion, A.; Raymond, M.; Ménard, N. (2006) Gorilla susceptibility to Ebola virus: the cost of sociality. Current Biology 16 (13), R489-R491. (Abstract available on CAB Abstracts)

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