The Hainan gibbon is the rarest ape on Earth, with its entire population squeezed into a single nature preserve on a single island off the coast of mainland China.

The island of Hainan was home to about 2,000 of these gibbons in the 1950s, but they were obliterated over the next few decades by rampant hunting and habitat loss. Although they’re now protected under Chinese law, their population is still down to just 25 individuals living in three social groups — or so we thought.