The rarest primate on Earth
On a single forested ridge in China's Hainan Tropical Rainforest National Park is the entire world population of the Hainan gibbon (Nomascus hainanus). As of early 2024, the population stands at just 42 individuals, making it the world's rarest primate. This is a fragile recovery from a low point of fewer than 10 individuals in the 1970s. In the 1950s, more than 2,000 Hainan gibbons lived across the island, but their numbers plummeted due to habitat destruction from logging and the expansion of rubber plantations, as well as poaching. Today, they are confined to the Bawangling National Nature Reserve, a mountainous area that became their last refuge as lowland forests disappeared.
The Hainan gibbon is a species of lesser ape, meaning it is smaller and distinct from great apes like gorillas and chimpanzees. They have striking sexual dichromatism: adult males are entirely black, while adult females are a golden-buff color with a black patch on their head. Infants are born a golden color and turn black within a few months. Females revert to the golden hue upon reaching sexual maturity. These apes are almost exclusively arboreal, spending their lives in the treetops and moving with incredible speed and agility by swinging between branches, a method of locomotion called brachiation. They rarely, if ever, descend to the ground. Their diet consists mainly of ripe, sugar-rich fruits like figs, supplemented with leaves, flowers, and insects.
A song of survival
One of the most distinctive behaviors of the Hainan gibbon is its daily dawn chorus. Mated pairs perform complex, coordinated duets at sunrise. These loud, haunting songs can travel over a kilometer through the dense forest and reinforce the pair's bond and advertise their territory to other gibbon families. The vocalizations are complex, with the male and female singing different, alternating parts. Bachelors also sing solos in an attempt to attract a mate. This vocal communication is a tool for researchers and rangers, who use the unique "vocal fingerprints" of the calls to monitor the gibbons' locations and family groupings without disturbing them.
Intensive conservation efforts are underway to secure the gibbons' future. An important intervention has been the construction of artificial canopy bridges. After a typhoon in 2014 caused landslides that created large gaps in the forest canopy, conservationists installed mountaineering-grade rope bridges to connect the fragmented areas. Cameras confirmed that after an initial period of hesitation, the gibbons began to use the ropes to cross the gaps, allowing them to access food and mates. In addition to habitat restoration, which includes planting their favorite native food trees, local communities are involved in conservation, and patrols work to prevent any remaining threats from poaching.