Photo taken on Oct. 28, 2017 shows two Hainan gibbons on a tree at the Bawangling National Nature Reserve in Changjiang, south China's Hainan Province. The Hainan gibbon, or Nomascus Hainanus, is the world's rarest primate, and probably rarest mammal species. Once numbered around 2,000 in the 1950s, they underwent a sharp decline in the late 20th century largely due to habitat loss and hunting. Typically living in rainforest trees over 10 meters tall, the Hainan black crested gibbon (Nomascus hainanus), with long arms and legs but no tail, rarely sets foot on the ground, making captive breeding difficult. (Xinhua/Huo Yongyi)
