Researchers have discovered a population of 200 of the world’s rarest orangutans hiding in the forests of Indonesia.

The previously unknown population was spotted by conservationists near the 140 square km Batang Park in the island of Borneo, according to the Wildlife Conservation Society (WCS).

The International Union for Conservation of Nature has enlisted all the subspecies of Bornean orangutans as endangered, LiveScience reported.

However, scientists have estimated that just 3,000 to 4,500 individuals are left in the subspecies known as Pongo pygmaeus pygmaeus, making them the most severely threatened.

Two thousand of those live in the Malaysian state of Sarawak in Batang Ai National Park and Lanjak-Entimau Wildlife Sanctuary, researchers say.

As conservations with WCS and other groups surveyed the region in February this year, they found a total of 995 orangutan nests, including fresh nests that indicated the rare population was recently using the area, the report said.

Researchers studying fresh nests left by wild orangutans in Indonesia have, previously, found they are incredibly complex.

They have found that orangutans bend and interweave living branches about 3-cm-wide to form the nest.

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