A novel behavioral paradigm for innate predator fear memory in rats

Understanding natural fear responses in rodents provides valuable insights into the mechanisms underlying stress and anxiety.

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.

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).

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.

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.