Olfactory but not vomeronasal mediation of scent marking by male golden hamsters.

Although olfactory and vomeronasal projections to the olfactory bulb and to the rest of the brain are quite distinct, it is not clear how the functions of these two chemosensory systems differ. In these experiments we attempted to determine the roles of the main olfactory and vomeronasal sensory systems in mediating scent marking by male golden hamsters, a behavior known to be stimulated by odors of other hamsters. Lesions of the main olfactory mucosa by irrigation of the nasal cavity with a solution of zinc sulfate dramatically reduced the frequency of marking. The degree of reduction in marking was correlated with an independent test of ability to detect volatile odorants. In contrast, surgical removal of the vomeronasal organ had no effect on marking frequency. Thus scent marking by male hamsters is primarily mediated by the main olfactory system and does not require the presence of the vomeronasal system. These results are discussed in the context of a theory that stresses the importance of the main olfactory system in pattern recognition and, in particular, in many types of social recognition.