A baby orangutan found abandoned and almost dead has made a swift recovery at an Indonesian rescue centre, and has been filmed playing happily with another young ape.

Gito was discovered dumped in a cardboard box in August under the baking sun on the Indonesian part of Borneo island, with rescuers initially believing the primate was dead due to his "mummified" appearance.

A team from International Animal Rescue (IAR) picked up the endangered Bornean orangutan, who had been kept as a pet by a local village head, and rushed him to their centre.

Gito -- who is less than a year old -- was suffering from multiple ailments but has recovered strongly, and was recently released from quarantine and introduced to another male baby orangutan, Asoka.

New footage released by IAR showed their first encounter, with the apes appearing wary when initially introduced at the orangutan rehabilitation centre on Borneo.

However, it was not long before the pair were playing happily together on a wooden climbing frame.

Asoka was also rescued on Borneo several months ago after a villager found him abandoned in the jungle and handed the ape over to IAR, although he was in a far better condition than Gito.

Gito is doing much better than when he was found suffering from dehydration, malnutrition and a skin infection, but his caregivers warn there is a long road ahead.

IAR programme director for Indonesia, Karmele Llano Sanchez, said Gito would still need to take part in "jungle school" -- a scheme designed to prepare orangutans for life in the wild -- before he could be released.

"It's going to take five to seven years before he is ready to be released into the wild," she told AFP.

Bornean orangutans are classified as endangered species by the International Union for Conservation of Nature and are protected under Indonesian law.

But their jungle habitats are being destroyed by the rapid expansion of palm oil and pulp and paper plantations, while locals view the apes as pests and sometimes target them.

Hundreds of Bornean primates were also rescued last year as massive, smog-belching forest fires ravaged the island. The fires, started to clear land for plantations, are an annual occurrence, but in 2015 were the worst for some years.