The author, alumnus of a Goodall year of Chimpanzee observation, struck out on his own for a field study of the elusive fruit-eating orangutan in the inhospitable jungles of Borneo and Sumatra. MacKinnon, grandson of Ramsay MacDonald, is made of stern stuff indeed, a prerequisite to coping with leeches, threatening animals and vegetation, rampaging river currents, etc. He did locate his subjects, which unlike most other primates, proved to be of a solitary nature -- the clans fairly well dispersed until good feeding areas brought them together. MacKinnon observed mothers and babies, matings (both peaceful and violent), feeding patterns and the curious territorial vocalizing of the old non-mating males -- group leaders protecting space for their descendants. He also points out the dangers to existing orangutans -- it's the old story of human encroachment paring the range. For those who fancy these slow-moving, ""melancholy"" primates swinging hand over hand through an exotic landscape -- an informative and jaunty journal.