Since Darwin, biologists have recognized that social animals in nature must balance the need to find food and mates, often competing for both, with the necessity to avoid capture by a predator. Unlike the chronic problem of failing to obtain food and mate, one failure to avoid a predator is catastrophic to future lifetime fitness. We should, therefore, expect that the minute-to-minute behavior of a wild animal reflects these competing selection pressures. Predator avoidance in primates includes freezing, fleeing, vigilance, and alarm calls. Predation on arboreal primates has been described anecdotally in several species. There is little research specifically on predator avoidance in Alouatta palliata, the mantled howler monkey, in Costa Rica. This research will study whether they have predator avoidance behaviors. I hypothesize that A. palliata in La Selva Research Station will exhibit predator avoidance in response to aerial predators. Research will be conducted on a protected reserve with 1,536 hectares of both primary and secondary forest at La Selva Research Station located in Heredia Providence, Costa Rica in May 2022. A. palliata are black, long, and stocky, with brown or yellow saddles on their sides, and can grow to be 22 to 36 inches long and weigh 11 to 15 pounds. A. palliata's predators are harpy eagles (Harpia harpyja) crested eagles (Morpheus guianensis), black hawk eagle (Spizaetus ornatus), jaguar (Panthera onca ocelot), ocelot (Felix pardalis), tayra (Eira barbara), boa constrictor (Boa constrictor), and anaconda (Eunectes marinus). Methods for study will include a 10-minute continuous-focal sampling followed by an instantaneous scan sample. I will record ecological variables such as resting and sleeping site height and the presence of vines at resting and sleeping sites, as well as the number of subjects and their sex, the presence or absence of predators, and behaviors such as vocalization, freezing, vigilance, fleeing, feeding, and resting. I will compare these behaviors in the presence and absence of predators.