The “whoop” vocalizations were almost all recorded on the NAWAC ARUs away from camp. Internal NAWAC discussions regarding the whoops almost invariably turn to how the vocalizations are kindred to—yet distinct from—gibbon vocalizations (gibbons are not great apes; they are lesser apes). The Area X “whoop” vocalizations are almost always multi-tonal in nature. Unaffiliated wildlife biologists and primatologists have also remarked on the primate-like nature of the vocalizations and their similarity