The sexual behaviour of Triturus cristatus cristatus consists of a prolonged period of static display, with bouts containing the two different tail movements Lash and Fan, followed by spermatophore transfer. There is evidence that Fanning fatigues males and that its rate and duration are under energetic constraints. The frequency of Fanning (Hz) drops gradually during a bout, and bouts get shorter as time goes on while the intervals between bouts get longer. Males who use more bouts have longer intervals between them. As a male undergoes repeated sessions of static display, the maximum lengths of Fan bouts conducted in each session decrease over time. Hence there are trade-offs between the rate and duration of display activities. These results are consistent with a role of viability-indicator models of intersexual selection in the evolution of the courtship display. When males are courting in the presence of a rival male, they significantly increase the number of Fan beats in each bout and the number of bouts conducted before attempting a mating. They also decrease the duration of intervals between bouts. A solitary male is probably selected to give a shorter, less intense display to a female in order to save time and to prevent the fatigue that would reduce his capacity to display to the next female.