Making contact with another species, interacting with one of our nearest relatives on an almost human basis, is an unforgettable experience. As an 8-year-old orangutan took hold of my hand and led me towards a tree to go climbing, I felt a lump come to my throat. I was standing in the rainforest of Indonesia’s Central Kalimantan province, on the island of Borneo, at Tanjung Harapan orangutan rehabilitation centre in Tanjung Puting National Park. It was feeding time for the rehab orangs, and having had his fill of bananas and a horrible-looking milk slop, this juvenile wanted to play.

The tree he chose was too flimsy to accommodate my weight, but still the orang didn’t let go of my hand as he climbed, swung, hung upside down and displayed all of the amazing arboreal agility for which orangutans are famous. Whenever he needed to use the limb that he had extended to me, he would deftly change to another hand or foot, always keeping a firm grip on my hand.

Orangs have very human eyes, and their facial expressions seem similar to ours, despite their lack of protruding lips, their small noses and their big, projecting snout-like lower faces; the longing face that he turned towards me was that of a child desperately seeking parental affection. It was the skin and the hair on his arms, and especially the very human hands, that brought home how closely related I was to the animal hanging upside down next to me. The skin visible below the sparse orange hair on the arms looked exactly like a darker version of my own, and the black hand holding mine had fingernails, an opposable thumb and even fingerprints. Only the fact that the thumb was much smaller than on humans spoiled the resemblance.

My newfound friend was one of the orangutans being rehabilitated in Tanjung Puting after spending years as an illegal pet. The idea is to feed the "patients" enough to keep them healthy, while keeping the diet monotonous enough that they want to forage on their own to supplement the free meals. The younger orangs are taught to build nests in the trees to sleep in, to protect them from wild pigs, and are otherwise encouraged to leave the comfortable life of a pet behind and rejoin the wild. With a total wild population variously estimated between 8,000 and 25,000, spread between the islands of Sumatra and Borneo, every extra individual reintroduced to the wild counts.

With population figures like these, orangutans are doing better than mountain gorillas, of whom there are less than 600 left in the wild. However, habitat destruction, due to logging and clearing land for farming and establishing plantations, along with capturing baby orangs for pets (a process usually involving killing the mother) means that their future is far from secure. There are three places where rehabilitation is being attempted: Tanjung Puting, Bukit Lawang in northern Sumatra, and Sepilok, near Sandakan in Sabah, the northeastern corner of Borneo that forms part of Malaysia.

I had visited Bukit Lawang nine months earlier, and while the orangutans were wonderful to see, the vast amount of litter left behind by hordes of Indonesian day-trippers from Medan, as well as the dozens of snap-happy tourists jostling for position at the feeding platform, detracted somewhat from the experience. In contrast, I was the only tourist on hand this day for feeding time at Tanjung Harapan, and there was none of the piles of plastic wrappers, bottles and cans that mar every other place of natural beauty that I saw in Indonesia.

This cleanliness is the result of Dr. Birute Galdikas and her stern anti-litter policies. Born in Canada, she is one of "Louis’ Ladies," a group of female primate researchers who started work under the guidance of Dr. Louis B. Leakey, the famous Kenyan palaeontologist. Other members of this select group include Jane Goodall, the famous chimpanzee expert, and Dian Fossey, killed in Rwanda in 1986 while studying her beloved mountain gorillas. Dr. Galdikas has been working at Tanjung Puting National Park since the early 1970s, during which time she and her co-workers have tried to rehabilitate hundreds of orangutans. In the 1970s, one of her colleagues, Gary Shapiro, worked for years teaching sign language to two young orangs, Rinnie and Princess.