Androgen influence on male mouse ultrasounds during courtship

Ultrasonic vocalizations are emitted by adult male mice (Mus musculus) shortly after an adult female or her odor are encountered, possibly as an early part of courtship behavior. Consistent with this hypothesis, it was found that castration of adult male mice increased the latency to first ultrasonic vocalization in response to an adult female. In addition, castrated males, subsequently injected once with 200 μg of testosterone propionate, reduced their latency, whereas oil-injected castrates did not.