Batang Ai National Park is part of the region’s largest trans-national protected area for tropical rainforest conservation. The 24 sq km park adjoins the Lanjak-Entimau Wildlife Sanctuary in Malaysia and the Bentuang-Karimun National Park in Indonesia. Together these totally protected areas cover almost 10,000 sq km and form a sanctuary for one of the few viable orang utan populations in Borneo (estimated at over 1,000 animals) as well as many other endangered species. For conservation reasons, Batang Ai National Park is the only part of this area open to visitors, but as it has the highest orang utan population density in central Borneo (up to 1.7 animals per sq km), there is a good possibility of seeing wild orang utan. However orang utan sightings should be regarded as a bonus not as a guaranteed experience.