Sumatran orangutan - Population & Distribution

Only 7 of the 13 subpopulations considered viable in the medium to long term

Previous Population and Distribution
The Sumatran orangutan is considered to have declined by more than 50% over the eight years until 2000. During 1998 and 1999, losses are reported to have reached a rate of about 1,000 orangutans per year.

Current Population and Distribution (Expand the map)
Historically, the Sumatran orangutan was distributed over the entire island of Sumatra (and even further south into Java), but its range has been restricted to the North of the island, and it has now been confirmed that orangutans do not inhabit the majority of the areas south of Lake Toba where they were previously thought to exist.

It is estimated that Sumatra has about 7,500 orangutans, distributed over 21 forest blocks. Of these, only three contain over 1,000 orangutans, and are found in the Leuser Ecosystem, one of the largest tracts of forest in the volatile northern part of the island.

There are 13 identified orangutan populations on the island, of which probably only 3 contain more than 500 individuals, with 7 estimated to contain 250 or more individuals. Six of the seven are believed to be losing 10-15% of their habitat each year to logging, and it is expected that these populations will rapidly decline.

Where populations are smaller, such as in West Batang Toru, and the estimated rate of habitat loss is relatively low (2% annually), numbers may persist longer than other populations if current conditions do not change.