Fieldwork conducted from 2015-2016 meant finding trails and nest sites in The Virunga Volcanoes area on the border of Rwanda and the Democratic Republic of the Congo (DRC). Genetic analysis was also conducted of 1,100 fecal samples to identify individuals.
In the mid-1980s the Virunga Volcanoes area had approximately 250 gorillas and in 2010, 480 were counted.
The most recent survey counted a minimum of 604. When combined with the estimated 400 gorillas in Bwindi Impenetrable National Park, Uganda, there are now 1,004 mountain gorillas, the survey states.
In a tweet on Thursday, Virunga National Park said: “Incredible news for conservation and much needed wonderful news for Virunga.”
Mike Cranfield, Africa Director for veterinary project Gorilla Doctors which cares for injured and ill mountain gorillas, said on its website the results were “truly remarkable” and “far exceeding our expectations”.
The survey was conducted by the park services of the three countries, non-governmental conservation organisations and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Mountain gorillas, a subspecies of the eastern gorilla, have longer hair, jaws and teeth than most other species. Adult males grow a patch of grey hair on their back and hips, giving them the ‘silverback’ moniker.