The society is to release its findings on Tuesday at a meeting of the International Primatological Society in Edinburgh. Conservation society scientists said the continuing threat of Ebola precluded a change in the gorilla’s status. But the discovery was mainly stirring excitement.

“This is the light of hope you look for,” said Richard G. Ruggerio, a conservation biologist at the United States Fish and Wildlife Service. But he cautioned that the large gorilla populations in the two studied tracts, which cover 18,000 square miles, should not lead to complacency. “It’s a different kind of alarm call, an opportunity that is increasingly rare on this planet  to do something before there’s a crisis,” he said. A separate global update on primates is being issued Tuesday at the Edinburgh meeting, showing that  with a few exceptions  forest destruction and, increasingly, hunting for meat, pets and Chinese medicinal products are imperiling monkeys and other primates, from Congo Republic to Cambodia.