A critically endangered orangutan has been brutally tortured and decapitated in Indonesia

The headless corpse of an orangutan, which appeared to have been brutally tortured, was found in a river in central Borneo, Indonesia, prompting an investigation by authorities.

A villager came across the bloated corpse of the male Bornean orangutan on Monday (15 January), which looked like it had been in the water for days, according to a local conservation agency.

In addition, to the decapacitated head, the animal was missing all its hair and covered in wounds. Its arms were also almost completely severed, suggesting it was the victim of horrific abuse before being killed.

Adib Gunawan, head of the Central Kalimantan Conservation Agency, said his organisation would be coordinating with police to find out who the perpetrators were, Mongabay reports.

The corpse was buried hastily by local authorities, due to fear of disease, before a proper autopsy could be conducted. This prompted criticism from conservationists, who said it would have helped the investigation.

"We could have checked its lungs to see whether the orangutan died from drowning or was killed before it was thrown into the river," said Ramadhani, a director at the Center for Orangutan Protection. "Wildlife deaths must not be taken lightly. We must follow procedures first before we bury the body."

The Bornean orangutan, which is one of man's closest living relatives, is considered 'Critically Endangered' by the International Union for Conservation of Nature due to the twin threats of deforestation and poaching.

The animals are seen as pests by palm oil plantation owners because they sometimes eat palm fruit. These farms have encroached on much of the orangutan's habitat. As a result, many orangutans are killed, despite them being protected by law.

In addition, captured live orangutans are also highly sought after from the illegal pet trade, making them very valuable.