The Danum Valley Conservation Area is one of the most pristine and biologically rich rainforests in Southeast Asia, and a haven for mammal enthusiasts. Covering over 43,000 hectares of undisturbed lowland dipterocarp forest, it is home to an impressive array of wildlife, including over 120 species of mammals. Among its most celebrated residents are the Bornean orangutan, pygmy elephant, Sunda clouded leopard, and Malayan sun bear. The valley also supports thriving populations of red leaf monkeys, giant flying squirrels, binturongs, and mouse deer, as well as rarities such as the western tarsier and the Sunda leopard cat. With patient observation—especially during night drives and guided treks—visitors may also glimpse elusive species like the marbled cat, slow loris, or clouded leopard. Danum’s exceptional biodiversity and relatively undisturbed habitat make it one of the best places in Borneo to witness the island’s unique and often endangered mammalian fauna.