Proboscis Monkey , large, long-tailed primate found on the island of Borneo. The adult male has a large, flat, fleshy nose that droops downward over the chin and may function to attract females or to radiate excess body heat. Males measure up to 76 cm (up to 30 in) in head and body length; the females are shorter. Proboscis monkeys are chiefly arboreal and eat leaves and fruit, but they are also capable swimmers, taking to waters of mangrove swamps and delta regions, where they are commonly found. They are chestnut red on the back, shading into cinnamon and white on the face and belly .