A novel behavioral paradigm for innate predator fear memory in rats.

BACKGROUND: Understanding natural fear responses in rodents provides valuable insights into the mechanisms underlying stress and anxiety. NEW METHOD: In this study, we developed a novel behavioral paradigm to assess fear responses in Long-Evans rats using a combination of natural and artificial predator cues: coyote urine and a remote-controlled (RC) artificial snake. These cues were integrated into a two-choice compartment arena to evaluate ethologically relevant defensive behaviors, including avoidance, freezing, head-out risk assessment, and escape. RESULTS: The coyote odor alone produced only a mild fear response (freezing during 5% of the first exposure session), while the RC snake elicited freezing during 33% of the session. Combining the two cues elicited a more robust fear response (39% freezing) and potentiated the behavioral significance of the coyote urine so that it robustly served as a reminder cue for fear memory during subsequent testing over 3 days (freezing 19%, 21% and 32%). The combination of odor and RC snake also produced reliable avoidance during the first exposure (92% of time in safe compartment). The avoidance remained high during subsequent days only if the odor cue was present (81%-90% avoidance). COMPARISON WITH EXISTING METHODS: The two-chamber design offers robust, measurable behavior compared to similar tasks that use an open field with predator cues. Avoidance and freezing have traditionally been induced by painful stimuli. CONCLUSIONS: The suggested paradigm can be useful for investigating mechanisms underlying fear and anxiety and predator-prey interactions. It balances ecological validity with experimental control, advancing the study of fear-based behaviors.