Olfactory Discrimination As an Isolating Mechanism Between Peromyscus maniculatus and Peromyscus polionotus

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Abstract
Experiments were designed to clarify the role of olfactory stimuli in sexual isolation between the closely related and allopatric mice, Peromyscus maniculatus rufinus and P. polionotus leucocephalus. Experimental animals were tested for responses to odors of the opposite sex of each species. Results with both sexes of P. maniculatus revealed consistent responses oriented to odors of their own species. Reactions of P. polionotus suggested no strongly developed species-oriented responses. Control experiments indicated that the significant differences in preferences of P. maniculatus were due to perception of the differences in odors. P. maniculatus males responded to homospecific estrous odors by increased activity. Considerations of the ecology of both species and the results of the present experiments suggest that, along with other sensory stimuli, olfactory cues may be important in pair formation and timing of sexual activity of the pairs. Individual recognition may also be involved but was not adequately tested. Choice of a mating partner does not reside with either sex alone. The species-oriented behavior of P. maniculatus is suggested to be a result of selection for species discrimination produced by sympatry with other species of Peromyscus. Conversely, the lower level of sexual isolation in P. polionotus leucocephalus may be a result of its geographical isolation.