COURTSHIP ULTRASONIC VOCALIZATIONS AND SOCIAL-STATUS IN MICE

A series of experiments was conducted to investigate whether the poorer sexual performance of subordinate than dominant male mice, Mus domesticus, was linked to lower sexual motivation. Ultrasonic calls uttered by a male in the presence of a female were used as an index of sexual interest. Males were housed in pairs for 5 days and dominant/subordinate roles were assigned. Subordinates, when tested in their home cage immediately after the removal of the dominant male, uttered more ultrasounds than the latter. When the dominant male was tested before the subordinate, there was no difference in the number of ultrasounds uttered and the subordinates' performance was consistently poorer. The fewer calls recorded when subordinate males were tested after the dominant partner was not associated with less defence/escape behaviour, nor could it be explained as habituation to female odour, as a consequence of being tested after the dominant partner. Within sexually experienced pairs, the urine of dominant males interacting with a female for 3 min reduced the number of ultrasounds uttered by the subordinate in the presence of a female. It is suggested that an inhibitory factor in the dominant male's urine functions as an indirect competitive mechanism when direct competition is prevented by removing the dominant subject. © 1991 The Association for the Study of Animal Behaviour.