The sumatran orang-utan is endemic to Sumatra island and is particularly restricted in the north of the island. There are small populations in the North Sumatra province along the border with NAD (the province of Nanggroe Aceh Darussalam), particularly in the Lake Toba forests. A survey in the Lake Toba found only two habited areas, Bukit Lawang (defined as the animal sanctuary) and Gunung Leuser National Park.