Mountain Gorilla Census Finds Increased Population in Uganda's Bwindi Impenetrable National Park

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Total world population of endangered species now stands at 880

KAMPALA, Uganda, November 13, 2013 -- Despite conflicts in surrounding regions that potentially threaten mountain gorillas, results from a 2011 census has found that Uganda's mountain gorilla population has grown.

The census, conducted in 2011 in Bwindi Impenetrable National Park, Uganda, confirms a minimum population of 400 mountain gorillas, up from 302 in 2006. The total world mountain gorilla population now stands at a minimum of 880. The official result was released today by the Uganda Minister for Tourism, Wildlife, and Antiquities Hon. Maria Mutagamba alongside representatives of the Uganda Wildlife Authority.

The increase in the Bwindi population since the last census is attributed to both population growth and improved censusing techniques of these rare and elusive apes. "Despite mountain gorillas being among the most studied of the great apes, these latest results demonstrate the challenges of wildlife censusing. We continue to perfect these methods in order to improve our mountain gorilla conservation efforts in the future," explains Craig Sholley, mountain gorilla expert and vice president for philanthropy and marketing at African Wildlife Foundation (AWF).

In this latest census, teams systematically moved through Bwindi not once, but twice, looking for and documenting mountain gorilla night nests, and collecting fecal samples for genetic analysis. The first sweep was conducted with a small team from Feb. 28 -- Sept. 2, 2011; the second sweep was conducted with multiple teams from Sept. 10 -- Nov. 3, 2011. With the genetic analysis, scientists were able to determine how many unique groups and individuals were found by the field census teams through both sweeps, in what is referred to as a modified mark recapture method.

In short, the two sweeps of Bwindi allowed census teams to find more gorillas than a single sweep would have. Further, it is likely that some gorillas were missed by field census teams in the 2006 census of Bwindi's mountain gorillas. But all signs are that this population of mountain gorillas is indeed growing.

"These methods give us the clearest picture of the status of mountain gorillas in Bwindi that we have yet had," said Maryke Gray, a census researcher with the International Gorilla Conservation Programme (IGCP), a coalition of AWF, Fauna & Flora International, and World Wide Fund for Nature. "Even with evolving census methods, the results indicate this population has indeed increased over the last five years, and that is very encouraging for this critically endangered species."

Observes Augustin Basabose, Virunga Heartland director for AWF and interim director of IGCP, "The mountain gorilla is the only great ape whose population is increasing despite continuous pressure on its habitat. This positive trend is due to the strong collaboration among the three countries where mountain gorillas live and the collective efforts on the ground by park staff, surrounding communities and local government, and non-governmental organizations."

Mountain gorillas live in social groups and the census results indicate the 400 mountain gorillas in Bwindi Impenetrable National Park form 36 distinct social groups and 16 solitary males. Ten of these social groups are habituated to human presence for either tourism or research and included, at the time of the census, 168 mountain gorillas, or 42% of the Bwindi population. Of the 880 mountain gorillas now thought to remain in the world, 400 were confirmed in this Bwindi census and 480 were confirmed by a census in the Virunga Massif in 2010.

While Sarambwe Nature Reserve in the Democratic Republic of Congo, a protected area continuous with Bwindi and therefore potential habitat for mountain gorillas, was initially going to be included in the census, it was not possible to do so due to insecurity in the Sarambwe area.

The 2011 Bwindi mountain gorilla census was conducted by the Uganda Wildlife Authority with support from l'Institut Congolais pour la Conservation de la Nature and the Rwanda Development Board. The census was also supported by AWF through IGCP, the Max Planck Institute for Evolutionary Anthropology, Conservation Through Public Health, the Mountain Gorilla Veterinary Project, the Institute for Tropical Forest Conservation, and the Dian Fossey Gorilla Fund International.

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