Courtship ultrasonic vocalizations (USVs) of male mice have been well documented and are thought to have an important role in male-female communication, functioning as a type of sexual behavior known as precopulatory behavior. Since the recent discovery of their song-like structure, USVs have attracted numerous research interest (Holy and Guo, PLOS Biol, 2005). USVs have often been used to study biolinguistics, social behaviors, vocal communication, and disorders that involve abnormalities in social behavior, especially autism spectrum disorders (ASDs).

Because singing in some songbirds is acquired by vocal learning, it was hypothesized that a similar learning process may occur in mice; however, several studies revealed that vocalizations in mice are mainly determined genetically. Mice use specific call types depending on their genetic strain. However, we observed that the number of calls and types of call repertories differ among individual mice, even among mice from the same inbred strain, such as C57BL/6. We are now focusing on the individuality observed in mouse vocalizations and the neural and hormonal mechanisms underlying this process.