Failure of captive-born greater rheas (Rhea americana, Rheidae, Aves) to discriminate between predator and nonpredator models

The capacity to recognize and respond to predators can be lost by captive animals. Habituation to humans caused by the captive environment can be transferred to other stimuli, such as predators, a situation that conservation biologists wish to avoid. Greater rheas are threatened South American birds, for which there are plans for reintroduction programs in Brazil. The goal of this study was to evaluate the behavioral responses of captive-born greater rheas to different models of predators and nonpredators. Seventeen captive-born greater rheas, divided into four groups, from the Belo Horizonte Zoo, Brazil were studied. Three predator and three nonpredator models were presented to the birds and their behavioral responses recorded. Predators versus nonpredator models and the behavior of rheas in three experimental phases (baseline, models, and postmodels) were analyzed. Captive-born greater rheas modified their behaviors in the presence of both predator/nonpredator models, increasing alert and wary behaviors (alert, observing, and pacing behaviors: P?<?0.01), showing some degree of antipredator behavior persistence, but they were unable to discriminate between predator and nonpredator models (all behaviors: P?>?0.05). In conclusion, antipredator training should be implemented to develop the expression of this behavior before reintroductions are attempted.