40-KHZ AND 70-KHZ VOCALIZATIONS OF MICE (MUS MUSCULUS) DURING COPULATION

Ultrasonic vocalizations were tape recorded from five pairs of copulat ing mice and subjected to spectrographic analysis. As expected, the mi ce emitted numerous 70-kHz vocalizations. At the beginning of the test , before copulation began, 70-kHz calls were emitted almost continuous ly, while calls with lower spectrographic frequencies were not observe d. Subsequently, bursts of 70-kHz calling generally began shortly befo re mounts and intromissions and persisted until dismount. Intermixed w ith these 70-kHz calls were additional vocalizations of about 40 kHz. Calling rates were highest just prior to intromission. Once intromissi ons began, 70-kHz calls continued at a lower rate until dismount; howe ver, 40-kHz calls occurred infrequently. In a second experiment, the m ale was found to emit the majority of the 70-kHz calls and all of the 40-kHz calls. When the male was devocalized, few calls were detected, regardless of whether the female was able to call. If the male was not devocalized, high rates of calling were detected, even if the female was devocalized. (C) 1998 Elsevier Science Inc.