Census confirms increase in population of the critically endangered Virunga mountain gorillas

Blog | 7/12/10

The number on one of the world’s most charismatic and endangered species is in.

The analysis of the census conducted in March and April 2010 indicates that there were a total of 480 mountain gorillas, Gorilla beringei beringei, in 36 groups along with 14 solitary silverback males in the Virunga Massif, which includes three contiguous national parks: Parc National des Virunga in DRC, Volcanoes National Park in Rwanda and Mgahinga Gorilla National Park in Uganda. The only other location where mountain gorillas exist is Bwindi Impenetrable National Park in Uganda.

Along with the 302 mountain gorillas censused in Bwindi in 2006 and four orphaned mountain gorillas in a sanctuary in DRC, this brings the total world population to 786 individuals.

The last census undertaken in the Virunga Massif was in 2003, when the population was estimated at 380 individuals. The current figure represents a 26.3 % increase in the population of mountain gorillas in this area over the last seven years, which is a 3.7 % annual growth rate. This increase in the population occurred despite the killing of no less than nine mountain gorillas, in four separate incidents, during this time period.

Of the 480 mountain gorillas censused, 352 (73%) were habituated (349 in groups and three solitary males) and 128 were unhabituated (117 in groups and 11 solitary males).

Map generated from data collected during the census illustrating the location of each group and solitary males throughout the Virunga Massif.

Map generated from data collected during the census illustrating the location of each group and solitary males throughout the Virunga Massif.

“This population has made an absolutely remarkable recovery from the approximately 250 individuals that existed only three decades ago. This recovery is due to the relentless collaborative efforts of many organizations and institutions in the Democratic Republic of Congo, Rwanda and Uganda,” stated Dr. Augustin Basabose, Coordinator of Species at the International Gorilla Conservation Programme (IGCP).

The census itself was an exercise in collaboration, and IGCP played a lead role in attracting support for the census and coordinating all participating institutions and organizations. Over 1,000 kilometers were systematically walked by six mixed teams of seventy-two people from DRC, Rwanda, and Uganda. Teams covered the entire range and meticulously documented fresh signs of mountain gorilla groups. Genetic analysis of fecal samples collected were analyzed to identify and correct for any double-counting of individuals or groups, ensuring the most accurate estimate for the population.

IGCP's Maryke Gray works with a member of the Rwanda Development Board to collect fecal samples used to ensure an accurate census count. Photo taken March 27, 2010.

IGCP's Maryke Gray works with a member of the Rwanda Development Board to collect fecal samples used to ensure an accurate census count. Photo taken March 27, 2010 by a member of the census team.

Although habituated mountain gorillas are continuously monitored, periodic census of the population is a necessary step in conservation. “The census allows all of us working in conservation to create a benchmark. Like any census, it captures the population at a specific point in time. This benchmark allows us to assess the status of this population as a whole and adjust our conservation efforts accordingly,” explained Maryke Gray, coordinator of the 2010 Virunga Massif mountain gorilla census and Technical Advisor to IGCP.

The goal of the census was not only to assess the population level of the mountain gorillas, but their level of health as well. Analyses conducted on fecal samples will contribute to one of the most comprehensive health screenings of any wild ape population. The results will also be extremely valuable in order to make comparisons between populations, and between habituated and unhabituated groups. These results will not only serve as a baseline for understanding the health status of the mountain gorillas, but may also provide insights into past and future exposure to human pathogens.

The census not only recorded the presence of mountain gorillas, but also the presence of other large mammals and illegal activities like bamboo cutting and snares. The full report of the census, which will be available in 2011, will include details on population dynamics and distribution of the Virunga gorilla population as well as population structure and genetic composition. These details will provide a scientific basis from which IGCP and other conservation institutions and organizations will plan collective conservation efforts.

While the incredible increase in this population of mountain gorillas is clearly a good thing and cause for celebration, the threats to their existence are persistent. Recently, a coordinated patrol discovered and destroyed just over 200 snares in the Virunga Massif over a five-day patrol. Although poachers typically do not target mountain gorillas, the snares they set are a threat nonetheless.

“We in IGCP are proud of the contribution we have made to the conservation of mountain gorillas over the last 20 years and we continue to vigilantly support transboundary collaboration and those on the front lines in the parks and surrounding communities,” commented Eugene Rutagarama, Director of IGCP. “Collectively, we cannot let down our guard on the conservation of these incredible animals. While mountain gorillas are physically strong, they are also incredibly vulnerable.”

The Virunga Massif mountain gorilla census was conducted by the protected area authorities in the three countries: L’Institut Congolais pour la Conservation de la Nature, the Rwanda Development Board and the Uganda Wildlife Authority. The census was supported by the International Gorilla Conservation Programme (a coalition of the African Wildlife Foundation, World Wide Fund for Nature, and Fauna & Flora International), the Max Planck Institute for Evolutionary Anthropology, the Dian Fossey Gorilla Fund – International and the Mountain Gorilla Veterinary Project. The census was funded by WWF-Sweden, Fair Play Foundation, and the Netherlands Directorate General for International Cooperation (DGIS) through the Greater Virunga Transboundary Collaboration.

Pictures taken by census teams are available for viewing through Flickr.

For more information, contact Anna Behm Masozera, IGCP Communications Officer at +250 782332280 or abehm@awfafrica.org.

The International Gorilla Conservation Programme (IGCP) currently consists of Conservation International, Fauna & Flora International and the World Wide Fund for Nature. We recognise that the earth's survival is dependent on humanity's ability to maintain a healthy and balanced environment that includes all species of wildlife.