The Grauer's gorilla is one of two subspecies of the Eastern gorilla. The whole population of Grauer's gorilla lives in the forests of eastern Democratic Republic of the Congo (DRC) in Central Africa. In 1996 a civil war started in the DRC, which killed 5 million people. We wanted to find out what effect the civil war had on the population of Grauer's gorillas. We carried out field surveys and used data from local communities and park rangers and found that the global population had decreased by 77% since 1994. There are now only 3,800 individuals left. This makes this ape Critically Endangered on the IUCN Red List of Threatened Species and now makes both gorilla species (Eastern and Western) and all four subspecies Critically Endangered. This is the highest category of threat before extinction.