ABSTRACT
Foraging at night imposes different challenges from those faced during daylight, including the reliability of sensory cues. Owl monkeys (Aotus spp.) are ideal models among anthropoids to study the information used during foraging at low light levels because they are unique by having a nocturnal lifestyle. Six Aotus nigriceps and four A. infulatus individuals distributed into five enclosures were studied for testing their ability to rely on olfactory, visual, auditory, or spatial and quantitative information for locating food rewards and for evaluating the use of routes to navigate among five visually similar artificial feeding boxes mounted in each enclosure. During most experiments only a single box was baited with a food reward in each session. The baited box changed randomly throughout the experiment. In the spatial and quantitative information experiment there were two baited boxes varying in the amount of food provided. These baited boxes remained the same throughout the experiment. A total of 45 sessions (three sessions per night during 15 consecutive nights) per enclosure was conducted in each experiment. Only one female showed a performance suggestive of learning of the usefulness of sight to locate the food reward in the visual information experiment. Subjects showed a chance performance in the remaining experiments. All owl monkeys showed a preference for one box or a subset of boxes to inspect upon the beginning of each experimental session and consistently followed individual routes among feeding boxes.
