When they’re ready to start spending long periods of time alone, pupils at the center are still carefully tracked by technicians–most of whom come from nearby villages—to make sure they’re getting proper nutrition and not trying to revert to what they may have learned from humans. Every orangutan who “graduates” is tagged so it can be easily monitored.
“Even after they’re released, the orangutans still know to come back to the center when they get sick or injured,” says Andhani Widya Hartanti, one of the veterinarians for the center. Hartanti is currently on site because an eight-year-old named Dora got sick and needed her attention, but she says the orangutan is recovering quickly. “When an orangutan that was sick becomes healthy again, that’s my happiest moment at work,” Hartanti adds.
Only between 6,000 to 10,000 Sumatran orangutans are estimated to remain in the wild, making them critically endangered. Beyond its immediate goal of rehabilitating and releasing rescued orangutans, FZS is working toward two bigger, longer-term goals: Establishing a healthy new population of these endangered primates in the forests of Thirty Hills, where no orangutans were present before FZS began its work here, and protecting those forests for future generations of orangutans.
So far, the center has released 170 orangutans into the wild, making 30 Hills a rare success story for this species. The goal is to reach 350—the minimum required for a stable population—in the next two decades. But when asked how many orangutans this jungle could shelter, Pratje estimates 4,000.
“Thousands would be the minimum carrying capacity,” he says. “When we were deciding where to establish this new population, for me, we had to work here, because it’s exceptional to have such a large area of lowland rainforest.”