A survey in Kahuzi-Biega National Park found 181 individual Grauer's gorillas, an increase from the 168 individuals detected in the same sector in 2004, a release by the Wildlife Conservation Society said Thursday.
Related to the more famous mountain gorilla, the Grauer's gorilla is the largest subspecies of gorilla in the world, growing up to 500 pounds.
Also known as the eastern lowland gorilla, the subspecies is the least studied, due in large part to 15 years of political instability in the eastern Democratic Republic of Congo, the WCS said.
"We had several close calls with armed militias during the survey," Deo Kujirakwinja of the WCS said. "Thankfully, no one was hurt, and our census result is positive news for the conservation community."
The Grauer's gorilla is listed as "Endangered" on the International Union for Conservation of Nature's Red List and may number fewer than 4,000 individual animals.