Mouse Response to Aversive and Unconditioned Stimuli: Fox Urine and Rabbit Pellet Odors

Hoepner, Kari, Lauren Riegel, Rachel Zarem, and Elizabeth Hill

A study was conducted to determine the behavioral response of mice to aversive and unconditioned odors. We hypothesized that mice may have an innate aversion to the odor of a predator.  Two odors were compared in this study, fox urine and rabbit pellets, which were predicted to elicit certain responses based on the mouse’s olfactory perception of the scents. Thirteen mice of the C57BL/6 strain were tested; they had not been exposed to these odors, which also means that they had not been conditioned to react to either of them. Testing involved presenting the two scents in an apparatus with a center box and two arms (Plexiglas tubes).  Their reactions were measured using the time in each arm and the spent near each scent (timed by stopwatch). The results from the trials conducted in this experiment indicated that mice, on average, spent more time near the rabbit pellet odor (157.1 seconds) than the fox urine odor (72.6 seconds, paired t-test, p<.003). The hypothesis for this study was that mice would spend more time in the vicinity of the rabbit pellet odor than they would near the fox urine odor, and the findings strongly support the hypothesis. These data suggest that a mouse tends to avoid fox urine without any conditioning and that mice have less of an aversion towards rabbit pellets. Mice may have an innate instinct that leads them to avoid a predator’s scent, in this case the fox urine.

Keywords:  C57BL/6, fox urine, rabbit pellets, aversive and unconditioned odors