Cumulative Effect of Male's Displays in the Sexual Behaviour of the Smooth Newt Triturus vulgaris (Urodela, Salamandridae) 1

The relevance of the temporal spacing of signals to the timing and nature of the receiver's response during a communicative process was studied in the sexual behaviour of the smooth newt Triturus vulgaris . The possibility that a high rate of stimulation allows an accumulation of the effects of successive signals was investigated by comparing sexual interactions leading and not leading to spermatophore deposition. Results showed that the difference between the two types of interactions lay only in temporal features of the stimulation provided by the male to the female. Females, although in a comparable initial state of receptivity and exposed to comparable amounts of stimulation, performed the act triggering spermatophore deposition by the male only in some interactions. Display bouts, in which the male displayed at short intervals (less than 4 s), were longer in interactions where spermatophore deposition took place than in the others. This suggests that courtship was effective if accumulation of the effects of male displays could occur. This proposition was supported by the observation of a progressive change in the immediate female response to a given male display in the group where courtship bouts were longer. Our results indicate the existence of a system of tonic communication (see S chleidt 1973) during the sexual behaviour of the smooth newt, in which the effects of the male displays accumulate over time until some critical threshold is reached in the female.