I first developed an interest in gibbons during childhood visits to the St. Louis Zoo. At the time a pair of siamangs (Symphalangus syndactylus) occupied the central display in the zoo’s primate house. The cage was a stark enclosure, but a series of bars, shelves, and ropes allowed the occupants to showcase their speed and gymnastic abilities. When they were swinging around the cage, the siamangs captured the attention of almost all the visitors in the building, but during the remainder of the time, they were passed over for more visually conspicuous species such as prehensiletailed spider monkeys, mohawked tamarins, or estrous baboons. But I was drawn to the siamangs over even the great apes, which were housed in a separate building. In the siamang’s upright posture, round face, and pensive expression, I saw clear evidence of evolutionary continuity. It was then that I first began to dream of studying gibbons in the wild. But beyond the information printed on the zoo’s plaque, I knew nothing of gibbon behavior or ecology or even to what extent they had been studied in their natural habitat.