A simple threat detection strategy in mice

Results: We used an automatic behavior detection system in mice to quantify innate defensive behaviors, including freezing, flight, and rearing, to a series of looming visual stimuli with varying expanding speeds and varying initial and final sizes. Looming visual stimuli within a specific “alert range” induced flight behavior in mice. Looming stimuli with an angular size of 10–40° and an expanding speed of 57–320°/s were in this range.

Stimuli with relatively low expanding speeds tended to trigger freezing behavior, while those with relatively high expanding speeds tended to trigger rearing behavior. If approaching objects are in this “alert range,” their visual features will trigger a flight response; however, non-threatening objects, based on object size and speed, will not. Conclusions: These results indicate a simple strategy in mice that is used to detect predators and suggest countermeasures that predators may have taken to overcome these defensive strategies.

Keywords: Automatic behavior detection, Innate fear, Alert range, Freezing, Flight, Rearing