Villagers heard it first: A male gibbon singing a duet with a female on tropical Hainan island off the coast of China. It means that love is in the air, or at least the gibbon version of it, and in this case, it's big news, reports the BBC. That's because the Hainan Gibbon has the unwanted distinction of being the world's rarest primate. About 2,000 roamed the island in the 1950s, but the number plummeted to single digits in the 1970s. Today, the figure has just inched back above 30, which is why that forest duet—featuring the "flute-like call of the male" and the "hooting" response of the female, per Mongabay—is such a welcome sound to researchers. In a new study in Onyx, they explain that the duet took place outside the known territory of the island gibbons, suggesting that the male and female were establishing a new family of their own.
"There are only five families of this species in the world, so every single new family formation is exciting news," says Philip Lo, a conservation officer who is co-author of the new report. If all goes well, a baby will be appearing in the next year or so. The Hainan Gibbon is the only one of 19 species of gibbons in the world showing a stable increase in numbers, even if the grand total is still under three dozen, reports the South China Morning Post. Over the years, conservationists have beefed up the presence of native fig trees the gibbons love to feast on, and they've educated locals on the importance of protecting the animal. The next big goal: reaching a population of 50, which would move the gibbon from "critically endangered" to "endangered." Lo is optimistic. "I can't imagine how sad it would be if Hainan rainforest lost this beautiful animal and its wonderful song." (Read more discoveries stories.)