Effects of laryngeal denervation on ultrasound production and male sexual behavior in rodents.

Adult male house mice (Mus musculus) and deer mice (Peromyscus maniculatus bairdi) were used to investigate the effects of partial denervation of the larynx on ultrasound production. In addition the masculine sexual behavior of vocalizing and muted males was assessed on tests with receptive females. For both species, unilateral transections of the inferior laryngeal nerve (ILN) significantly reduced the proportion of males that emitted ultrasonic vocalizations. However, the inability to vocalize did not prevent the display of male sexual behavior. Bilateral transections of the superior laryngeal nerve (SLN) failed to abolish ultrasound production in males of both species. These nerve transections, however, reduced the amount of ultrasound recorded during postsurgical tests, and in the case of deer mice, cuts of the SLN increased the latency to the first vocalization. The present results confirm the importance of the ILN in the neural control of ultrasonic vocalizations and indicate that, at least in laboratory tests, the ability to emit ultrasounds is not a necessary condition for the display of mating behavior in male rodents.