Gorilla, chimpanzee census kicks off in Bwindi

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Whereas the mapping and deployment of technical personnel took place two weeks ago, the official launch of the gorilla and chimpanzee census in Bwindi Impenetrable National Park begins on Tuesday, May 6, in the Ruhija sector, the eastern part of the Bwindi forest.

The census, coordinated by the Greater Virunga Transboundary Collaboration (GVTC) and the International Gorilla Conservation Programme (IGCP), has attracted several local and international conservation organisations, as well as authorities from Uganda, Rwanda and the Democratic Republic of Congo (DRC), where mountain gorillas are endemic.

Dr Andrew Seguya, the GVTC executive director, said that although mountain gorillas roam across the landscapes of all three countries, the census will begin on the Ugandan side.

“The census in the other two countries will start around March next year,” he noted.

Seguya, however, did not provide details as to why the ape census in Rwanda and the DRC will be delayed. A source intimated that the delay in counting gorillas in the Greater Virungas is due to insecurity in the DRC.

Meanwhile, gorillas are supposed to be counted every five years. Although the last census was conducted in 2018, the follow-up exercise planned for 2023 was halted due to the ripple effects of COVID-19. A total of 459 mountain gorillas were registered in Bwindi during the 2018 census.

Dr James Musinguzi, the executive director of the Uganda Wildlife Authority (UWA), underscored the importance of the gorilla census in helping to devise customised strategies for conserving the gentle giants and their habitat.

Musinguzi also revealed that although gorillas are the main focus, the census will also consider other species within Bwindi National Park, including other mammals. It will also identify possible illegal activities within the park and locate unauthorised access routes to the dense habitat. He estimated that the first phase of the exercise would last until July, before resuming in September this year.

The ongoing census is also expected to extend to the Sarambwe Wildlife Reserve, which is connected to Bwindi on the DRC side. However, the last census did not record many gorillas in Sarambwe.



In addition to Bwindi, Uganda’s other mountain gorilla population is found in Mgahinga National Park in the south-west. The smallest national park in Uganda, Mgahinga is part of the Virunga range (which includes Virunga National Park in the DRC and Volcanoes National Park in Rwanda), where the census has been delayed.

Data from the IGCP indicates that the 2018 Bwindi-Sarambwe census estimated 459 individuals. Combined with past Virunga census results, the total population of mountain gorillas was placed at 1,063 individuals. Meanwhile, in Uganda, Mgahinga National Park is home to one gorilla family comprising nine members.

How the gorilla census is done

Dr Gladys Kalema-Zikusoka, Uganda’s first wildlife veterinary officer, said, “Only 300 gorillas were recorded in 1997 when I first participated. The numbers are steadily increasing due to several interventions such as improved veterinary services, community engagement where locals are directly employed by the Uganda Wildlife Authority, revenue-sharing benefits whereby 20% of the fees from park entrance and 10% off each gorilla permit is given back to the communities.”

Kalema, the executive director of Conservation Through Public Health (CTPH)—an organisation also participating in the census—explained that the exercise mainly involves counting the nests made by both habituated and non-habituated gorillas. “Several groups of about five people each are formed to sweep the forest at a go, where they count the nests found, considering other factors such as the dung, whose diameter can be used to tell the size of different gorilla individuals,” she explained.

“Then we have to count backwards, tracing at least two more sets of the nests of the same group so as to make sure we do not miss out any individual,” Kalema added. For each gorilla group, Global Positioning System (GPS) coordinates are taken by the team carrying out the census. As mother gorillas tend to share nests with their infants, enumerators also rely on dung during the census.

With advancements in technology, the census now includes genetic studies, where paternity tests are carried out to determine how gorillas are related to one another. Although the results take some time, genetic analysis is reported to give more accurate results. “On our part as CTPH, we also utilise the opportunity to carry out some comparative health checks between habituated gorillas and the non-habituated ones,” Kalema remarked.

A source at IGCP, who preferred anonymity, said that although the census is currently taking place in Uganda, there are participants from Rwanda and the DRC. “And when it's time to count those in Rwanda and DRC, there will also be participants from Uganda,” he intimated. This is meant to make the process as transparent as possible. “We are avoiding circumstances where one country claims to have higher numbers than the actual, in order to boost their tourism sector,” the source added.

Chimpanzee census in Bwindi

Although the procedures for counting gorillas differ from those used for chimpanzees, the latter will be incorporated into the ongoing gorilla census.

“For the chimpanzee census, it will be spearheaded by the Jane Goodall Institute,” stated an official from the Uganda Wildlife Authority. As the census proceeds, teams will camp inside the forest for weeks and months to execute the assignment.

Bwindi

Located in south-western Uganda, Bwindi Impenetrable National Park is home to over 54% of the world’s remaining mountain gorillas. It is one of the most biologically diverse forests in Africa, with an altitude range between 1,160 metres and 2,607 metres above sea level. This rainforest—home to gorillas—is spread over a series of steep ridges and valleys that form the eastern edge of the Albertine Rift Valley.

The forest, which spans over 32,000 hectares, is known for its exceptional biodiversity, with more than 160 tree species, 120 species of mammals, 357 bird species, and 220 species of butterflies, among several reptiles. Due to its diverse features and ecological significance, the park was designated a United Nations Educational, Scientific and Cultural Organisation (UNESCO) World Heritage Site.

About gorillas

King Oyo and members of Tooro royal family during their gorilla tracking expedition in Bwindi national park on recently. (Credit: Juilus Luwemba)

Gorillas live in families headed by a dominant silverback, who determines the timing of activities and the direction of travel. A gorilla can weigh more than 200kg and live up to 50 years. A female gorilla has the same ovulation cycle as human beings and a gestation period of eight months.

“A female gorilla can have a maximum of six babies in her lifetime, with a child spacing of four and a half years,” explained Dr Kalema, adding that gorillas have a natural family planning method, which involves feeding the baby for at least three years.

Gorilla tracking remains a premium product for Uganda’s tourism sector. Bashir Hangi, the UWA public relations officer, revealed that gorilla tracking attracted 43,364 tourists in 2024, up from 41,412 in 2023.

“On an upward trajectory, the numbers have been increasing from 9,829 in 2020 to 15,736 in 2021 and 32,628 in 2022,” he noted.

In 2024, a total of 41,468 gorilla permits were sold, up from 38,836 in 2023, surpassing the pre-pandemic 2019 level of 39,627 permits sold.