Borneo is home to an incredible diversity of primates, many of which are found nowhere else on Earth. The island’s most iconic primate is the Bornean orangutan, a critically endangered great ape known for its intelligence, reddish fur, and solitary nature. Sharing the forests are the proboscis monkeys, easily recognized by their large noses and potbellies, which live in mangrove and riverine habitats. The Bornean gibbon, with its haunting calls and acrobatic swings, is a symbol of the island’s lush canopy. Several species of leaf monkeys and macaques, including the endemic Maroon langur and pig-tailed macaques, also roam the forest layers. At night, tiny western tarsiers and slow lorises emerge, adding to Borneo’s primate diversity. These species play vital ecological roles and are key indicators of the rainforest’s health, making their conservation a top priority.