Removal of the vomeronasal organ impairs predator odor detection in female golden hamsters

Abstract

The main and accessory olfactory systems of mammals are involved in the detection of predator odor; however, the relative importance assigned to each varies between studies. We examined the behavioral responses of vomeronasal organ removed (VNOx) and sham operated (VNOi) female golden hamsters (Mesocricetus auratus) to urine odor from a predator, the ferret (Mustela putorius furo). We quantified the duration and frequency of the defensive behaviors vigilant rearing and concealment, and the neutral behaviors grooming and investigation, in female golden hamsters in a visible burrow system. We found that VNOx females exposed to predator urine odor spent significantly less time in concealment and more time rearing than VNOi females. Further experiments in which females were exposed to formaldehyde odor showed that their behavioral responses to ferret odor differed from those to formaldehyde odor. This shows that the female hamsters’ behavioral responses are not adverse reactions to noxious odors, but typical reactions to predators. Golden hamsters have been laboratory-reared for over 80 years, but defensive behavior in females appears to be innate and can be impaired by surgical removal of the vomeronasal organ. Therefore, the accessory olfactory system, via the vomeronasal organ, plays a role in the detection of predator odor by golden hamsters, even though it has not been found to function in conspecific odor discrimination.