Sumatran orangutans study for nature's pass/perish entrance exam

I'm struggling to make friends here. Miriam, a 9-month-old orangutan orphan who's learning how to climb a tree, almost scales past her trainer when I approach. For good measure, she starts to cry. Another orangutan signals displeasure by emulating the sound of a Harley barreling toward me. In fact, the only one who tolerates me is 11-year-old Leuser, and not because the 42 air-rifle pellets lodged in his body have mellowed him. He's also blind.

At any zoo, these surly apes would bomb the aw-isn't-he-cute exam, but here at the world's most successful school for rescued orangutans, they're taught to get back in touch with their wild side. Even playtime is serious business. Passing, say, the test of recognizing a friend (another orangutan) versus a foe (a human logger) could spell life or death for these critically endangered icons of the old world jungle.

Everything happens here with one goal in mind: graduation day, when the shaggy students are set loose into the harsh Sumatran rain forest. But for the students to have a shot at survival, handlers must teach them to avoid humans at all costs, a tough task considering they need to be fed by humans.

"We need to take care of these confiscated animals and return them to the wild," says Ian Singleton, director of the Sumatran Orangutan Conservation Programme. "But we need to do it scientifically."

And real science doesn't involve a line of gawky tourists dangling bananas and posing for pictures. That's why this center at the far north of Sumatra – one of the main islands of Indonesia – is closed to the public and barely known to outsiders. Even if you made it to the nearby village of Batu Mbelin – where the specialty dish is fruit-bat soup and the humid air is clouded with mosquitoes, this part of Sumatra – is definitely not for the faint of heart.

I reflexively clench the door handle of Mr. Singleton's SUV as we cross over a rushing river on a wooden bridge. Palm trees line the one-lane road to this village, and in the distance, various plantations – chocolate, banana, papaya – dot the endless green of the hills.

"Kai berita," Singleton shouts in the local Karo Batak tongue to villagers we pass. He turns to explain, "I hate to be that white guy who drives by with the windows up and air-conditioning on."

With the locals, many of whom work at the rehab center, he's gained the reputation as a man unusually obsessed with orangutans, which are found only in the lowland forests of northern Sumatra and the nearby island of Borneo. They don't understand, at least initially, why he would offer the apes a hollowed-out block of wood with honey inside to play with, rather than just chicken and rice, the customary diet of pet orangutans. Turns out, it's a useful skill for wild orangutans to learn how to scrape honey out of a tree hole.

"The handlers come here thinking an animal is an animal, that as long as you feed them, they're fine," Singleton says. "But they're not. They need behavioral enrichment." Another trick to keep the students sharp is to tie up rice sacks with the food inside (they like any sweet fruit). "Some of them rip it open," he says. "But the smart ones untie the bag."

But you could say those are elective classes. Most of the orangutans come here either completely spoiled by their former owners – almost all military officers who keep them as illegal pets – or with injuries from clashes with farmers and illegal loggers. The injured receive medical attention, and former pets are quarantined for a few weeks and then transferred into a sprawling system of socialization cages. For the young ones, it may be the first time they've seen another of their kind. "Sometimes they don't have a clue how to take care of themselves," says Singleton.

The night before this jaunt, Singleton was up until 2 a.m. discussing X-rays with a Swiss surgeon who flies here for emergency surgeries.

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