Their transport may be rustic, their manners less than polished, but much has been invested in the orang-utans of Nyaru Menteng. It takes £12,000 and eight years to raise these Indonesian orphans to the stage where they can be reintroduced to the wild, to boost the population of one of the world's most endangered species.

Indonesia's orang-utan population has halved in the past 20 years, driven down to between 40,000 and 50,000 by illegal logging, poaching, forest fires and oil palm plantations. Nyaru Menteng, with 670 orang-utans the largest primate rescue in the world, is at the forefront of attempts to save the normally solitary great ape.

Speaking yesterday on the eve of World Habitat Day, Gilly Lloyd, of Borneo Orangutan Survival International, explained how their reintroduction programme works. “Most are found as orphaned babies and they have to be totally rehabilitated, with 24-hour care. Every day they are taken out into the forest to learn how to become orang-utans,” she said. “When they get to about 8 years of age we take them to one of a number of neighbouring islands, the first stage in releasing them back into the wild.”

Rehabilitating an orang-utan costs about £1,500 a year, but Ms Lloyd believes that it is worth it. “Orang-utans have such an important role to play in the rainforest that we cannot let such a species to die out. We owe it to them to save them.”

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