Predator odor induced defensive behavior in wild and laboratory rats: A comparative study

Laboratory rats are frequently used as animal models in research. Since the 1920s rats are bred and reared in laboratories which affects anatomy, physiology, and behavior responses. In the present study we exposed laboratory and wild rats to predator odor and comparatively analyzed their behavioral and physiological responses. In detail, Warsaw Wild Captive Pisula Stryjek (WWCPS) rats and Lister Hooded (LH) rats were exposed to the predator odor 2,3,5-trimethyl-3-thiazoline (TMT), their behavior was videotaped and blood samples were collected for subsequent serum corticosterone analysis. In both rat stocks, exposure to TMT induced avoidance behavior and increased freezing behavior. Notably, the increase in freezing was based on an increase number of freezing events in LH rats whereas WWCPS rats prolonged the mean duration of the single freezing events. Interestingly, TMT exposure lead to a serum corticosterone increase in WWCPS rats but not in LH rats. Furthermore, WWCPS rats generally expressed decreased but faster locomotor activity, as well as more grooming behavior than LH rats. Taken together, these data indicate differences in behavioral and physiological defensive responses to predator odors in the two rat stocks.