The Sumatran orangutan (Pongo abelii) is one of the two species of orangutans. Found only on the island of Sumatra, in Indonesia, it is rarer than the Bornean orangutan.
The Sumatran orangutan is endemic to Sumatra island and is particularly restricted to the north of the island. In the wild, Sumatran orangutans survive in the province of Nanggroe Aceh Darussalam (NAD), the northernmost tip of Sumatra. The primate was once more widespread, as they were found more to the south in the 19th century such as in Jambi and Padang. There are small populations in the North Sumatra province along the border with NAD, particularly in the Lake Toba forests. A survey in the Lake Toba region found only two inhabited areas, Bukit Lawang (defined as the animal sanctuary) and Gunung Leuser National Park. The species has been assessed as critically endangered on the IUCN Red List since 2000. It is considered one of "The World's 25 Most Endangered Primates."
A survey in 2004 estimated that around 7,300 Sumatran orangutans still live in the wild. Some of them are being protected in five areas in Gunung Leuser National Park; others live in unprotected areas: northwest and northeast Aceh block, West Batang Toru river, East Sarulla and Sidiangkat. A successful breeding program has been established in Bukit Tiga Puluh National Park in Jambi and Riau provinces.