A Novel Naturalistic Paradigm to Study Aerial Predator-Induced Fear

Thesis (Master's)--University of Washington, 2018Whether an animal is carnivorous or herbivorous, the need to exploit any foraging advantage while mitigating all risks is a major evolutionary pressure. The rat, although a small prey animal, has been able to employ these behaviors to adapt in nearly any environment and become the second most successful mammal on Earth. Historically to study fear behavior and avoidance in the rat, laboratories have utilized Classical Conditioning involving an electrical shock (unconditional stimulus) paired with a tone (conditional stimulus). While this has been proven to be a useful paradigm in understanding learned behaviors and their neural underpinnings, it cannot fully explain the success the rat has had. Multiple innate behaviors have been observed in the rat in response to naturally occurring stimuli, and many of these behaviors are designed to detect and evade predators. A well observed predator avoidance behavior in rodents is freezing or fleeing to an aerial predator or looming stimulus. To further explore this innate fear of aerial predators the present study designed a large arena in which the rat can forage for food and eventually encounters an attacking model owl. All rats immediately fled from the plunging owl and remained in the nest area where other fear behaviors were observed. To begin to understand the neural correlates involved in the observed behavior the basolateral amygdala (BLA) was temporarily inactivated with muscimol. With the BLA inactivated no fear responses were seen and the rat efficiently retrieved the pellet during the owl encounter. This novel paradigm provides a new way to investigate innate defense mechanisms rats use to avoid predation