In a dense strip of peat swamp jungle along the banks of Mangkutub River in the heart of Borneo, a conservationist aims his tranquilizer rifle at an orangutan high in a tree and fires two darts.

The giant, red-haired primate slides down the tree on its own and soon loses consciousness on the jungle floor.

In this Jan. 5 photo, conservationists from the Borneo Orangutan Survival Foundation examine a tranquilized orangutan during a rescue and release operation for orangutans trapped in a swath of jungle in Sungai Mangkutub, Central Kalimantan, Indonesia. The orangutans, which lost their habitat to the forest fires last year, were forced to live in the over-populated peatland forest along the river, raising fears that they would run out of food soon. (AP/Dita Alangkara)

A team of ten rescuers from the Borneo Orangutan Survival Foundation huddle around the adult male and perform a brief medical examination — checking temperature, teeth to determine rough age, taking a blood sample and inserting a chip under its skin — before preparing to transport the orangutan to a release site about 80 kilometers away, where they believe it will have more space to roam and be less threatened by forest fires.

Forest fires, often set illegally to clear land, have been an annual problem in Indonesia since the mid-1990s, but last year's was the worst in nearly 20 years, when blazes spread across 2.1 million hectares (8,063 square miles). They killed 21 people, damaged crops and caused respiratory problems for more than half a million.

In this Jan. 6 photo, conservationists of the Borneo Orangutan Survival Foundation release a rescued orangutan at a forest in Sungai Mantangai, Central Kalimantan, Indonesia. A team of foresters, veterinarians and technicians were deployed to rescue orangutans which lost their habitat to the forest fires last year and relocate them to a new location. (AP/Dita Alangkara)

The fires also encroached on the habitat of orangutans in central Borneo, forcing them to move closer to river banks, in some places along a strip of forest as narrow as 30 meters (yards) near the Mangkutab River. The population of the big apes got so crowded that experts worried they would starve and get into conflicts with people living nearby.

"Recent forest fires have made it difficult for orangutans to find food and this is very dangerous for them," said Ahmad Sayoko, coordinator of rescue and release mission.

In this Jan. 5 photo, conservationists of Borneo Orangutan Survival Foundation examine a tranquilized orangutan as they conduct a rescue and release operation for orangutans trapped in a swath of jungle in Sungai Mangkutub, Central Kalimantan, Indonesia. (AP/Dita Alangkara)

Most rescued orangutans were found in bad condition, apparently starving and some with cataracts. One had multiple air rifle pellets in its head and leg, a sign of conflict with humans.

Southeast Asia's Sumatra and Borneo islands are the orangutans' last homes on Earth, and environmentalists warn that the estimated 60,000 animals remaining could disappear from the wild within the next decade if steps aren't taken to protect them. Wild orangutans are also threatened by poaching and illegal logging.

In this Jan. 6 photo, a conservationist of the Borneo Orangutan Survival Foundation carries a tranquilizer gun as he moves through the swamp during a rescue and release operation for orangutans trapped in a swath of jungle in Sungai Mangkutub, Central Kalimantan, Indonesia. (AP/Dita Alangkara)

"We have to rescue and relocate them as soon as possible or they could lose their lives," said Kissar Odom, who works for the foundation. During the team's first operation in November, they rescued and relocated 39 orangutans, he said.

On this, the team's second operation, rescuers have spotted an orangutan nearly every ten minutes as they ride along in the boat, a sign that the area along the river has a higher population density than is healthy.

In a dense strip of peat swamp jungle along the banks of Mangkutub River in the heart of Borneo, a conservationist aims his tranquilizer rifle at an orangutan high in a tree and fires two darts.

The giant, red-haired primate slides down the tree on its own and soon loses consciousness on the jungle floor.