In the 1960s, it was believed that no more than about 4,000 orang-utans remained in the wild. Consequently, IUCN - The World Conservation Union - declared the ape an endangered species, demanding its world-wide protection. Nevertheless, the orang-utan today faces extinction because it is dependent on a rain-forest habitat that is rapidly being demolished due to human greed, and a growing human population.
Rijksen was among the first to make a detailed study of the ape in the wild, emerging as an authority on orang-utan conservation. In the late 1980s he became so alarmed by local...