The intense wildfires, burning mainly on Borneo and Sumatra islands, began in July and could continue until November, aggravated by a severe El Niño weather pattern, the government has warned.

“I think so far this looks quite similar to the 2015 fires,” said Karmele Llano Sanchez, co-founder of Yayasan Inisiasi Alam Rehabilitasi Indonesia (YIARI), who has worked in Indonesia for more than 20 years.

“It’s possible that in the months to come, they (the orangutans) will also be affected by not having enough to eat, not having enough room, enough habitat, and starvation.”

The world’s three species of orangutan are native only to Borneo and Sumatra.

YIARI, in the Ketapang region of Indonesia's West Kalimantan province, is now looking after 90 orangutans, after rescuing 49 since August, foundation spokesperson Heribertus Suciadi said.

Over the last three years, the center rescued three to five animals a year, he added.

The fires and haze have shrouded parts of Borneo, which also includes the Malaysian states of Sarawak and Sabah, in a hazardous smog that has also spread to Singapore and the Malaysian peninsula, forcing some schools to close and causing a spike in respiratory illnesses.

Sampurna, an orangutan that Reuters encountered in August, was found gasping for air and writhing on the ground in a palm oil plantation.

Sampurna died on August 30, the forestry ministry said last month.

Sanchez, who performed the necropsy on the great ape, said Sampurna died less than 12 hours after being rescued and had very dark lungs owing to respiratory problems, likening them to those of a heavy smoker.

From January to July this year, fires burned around 202,000 hectares (500,000 acres) in ⁠Indonesia.

No official data for subsequent months has been released, but non-governmental organisations estimate fires have burned at least 600,000 hectares more since.

In 2015, fires burned nearly 960,000 hectares, forestry ministry data showed.

“I think in general, what we see is that these orangutans that were surviving in these fragments of forest, and the forest fragments are becoming smaller and smaller and smaller,” Sanchez said.

Rescue missions

Once YIARI volunteers receive reports of orangutan sightings, they use a drone to determine the areas ravaged by the fires and whether orangutans were living there, Heribertus said.

Equipped with tranquilisers, rescuers then drive for hours to the burned forest to find the orangutans, sometimes using a net to capture the apes before taking them to safety.

The foundation has more than 200 staff, including firefighters and veterinarians.

“Fires are occurring in many areas. As a result, the orangutans are being displaced into plantations,” said Relly Susanto, a YIARI patroller.

On a recent August day at the YIARI center, orangutans swung through the trees and walked on vines, as youngsters ate fruit next to their mothers.

While there is no escape from the smoke even at YIARI, the centre is not currently at risk from the fires themselves and some of the rescued orangutans have been returned to the wild in safer locations.

At the moment, YIARI has enough capacity to take in the orangutans, Sanchez said. But with the fires showing little sign of abating, she is not sure how long that will last.

“It’s difficult to quantify how many orangutans will need to be rescued,” she said.

“One of our concerns is whether we’ll have enough capacity to really get all of these rescued orangutans into the facility.”