A study has found that gorillas are far more numerous than previously thought—although the animal remains critically endangered. Researchers estimate there are more than 360,000 western lowland gorillas living in the wild. Although this figure is about a third higher than earlier estimates, it represents a drop of 20% in just eight years. Around four-fifths of the gorillas do not live in protected areas. This means they are vulnerable to poachers, disease and the destruction of their forest habitat—“guns, germs and trees”, as the researchers put it. Professor Fiona Maisels of the Wildlife Conservation Society warns: “Just because there are rather a lot of does not mean they are not very, very vulnerable.” Gorillas breed slowly, giving birth only every four years. “It takes a very long time to build populations back up,” Maisels says.

The scientists covered about a quarter of the gorilla’s total range in western central Africa—an area the size of France—counting the number of nests that the gorillas made every night. They made their estimate for the gorilla’s entire range by taking into account the presence of people, roads and intact forest outside the surveyed areas. They also estimated the population of the central chimpanzee sub-species (which lives in the same range) by the same method, and found that the chimp population was also higher than expected.

Outbreaks of Ebola have also had a catastrophic impact on gorilla and chimp populations in recent decades, and it still lingers in remote regions today.