KINIGI, Rwanda (AP) Deep in the rainforest of Volcanoes National Park, a 23-year-old female gorilla named Kurudi feeds on a stand of wild celery. She bends the green stalks and, with long careful fingers, peels off the exterior skin to expose the succulent inside.

Biologist Jean Paul Hirwa notes her meal on his tablet computer as he peers out from behind a nearby stand of stinging nettles.

The large adult male sitting next to her, known as a silverback, looks at him quizzically. Hirwa makes a low hum ahh-mmm imitating the gorillas usual sound of reassurance.

Im here, Hirwa is trying to say. Its OK. No reason to worry.

Hirwa and the two great apes are all part of the worlds longest-running gorilla study a project begun in 1967 by famed American primatologist Dian Fossey.

Yet Fossey herself, who died in 1985, would likely be surprised any mountain gorillas are left to study. Alarmed by rising rates of poaching and deforestation in central Africa, she predicted the species could go extinct by 2000.

Instead, a concerted and sustained conservation campaign has averted the worst and given a second chance to these great apes, which share about 98% of human DNA.