In Georgia, a density of 15 hispid cotton rats per acre was considered the predator-limited carrying capacity. Mammalian predators did not have a substantial effect on population density. At densities higher than 15 per acre, mortality was high; below 15 rats per acre, predator-caused mortality was low. When diverse and mobile predators are present, they are more important than food, social interaction, or weather in limiting hispid cotton rat density. Also in Georgia, field enclosures protected from avian predators (covered with a net) were monitored for the effect of avian predators on breeding hispid cotton rat populations. The presence of the cover had no effect on seasonal recruitment or spring-summer mortality; however, autumn-winter mortality was greatly reduced with the cover in place. Avian predators, then, are apparently more important than mammalian predators. In addition, nonbreeding (winter) populations suffer substantial losses from predation, whereas breeding populations are either able to compensate by replacing lost individuals, are less vulnerable to predation, or both.