https://phys.org/news/2018-05-wild-mountain-gorillas.html

The last census conducted in the Virunga Volcanoes was in 2010, when the population was estimated to be a minimum of 480 gorillas. The current figure represents a 26 percent increase in the number of gorillas over a six-year-period, which is a 3.8 percent annual rate of increase. This increase is due to improved methods used in this recent census as well as actual growth of the population. The 604 gorillas were found in 41 social groups and 14 solitary males.

Conducting the census was a large collaborative effort among the park services of the three countries where mountain gorillas live, namely Rwanda, Uganda, and the Democratic Republic of Congo, several non-governmental conservation organizations, and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Routine censusing such as this one is a crucial part of adaptive management strategies to help determine whether a population is increasing or decreasing in size and decide if conservation efforts are effective or should be modified. The population of mountain gorillas in the Virunga Volcanoes numbered only about 250 gorillas in the mid-1980's.