The effect of environmental and social factors on the courtship and mating dynamics of the smooth newt, Triturus v. vulgaris
The effect of environmental and social factors on the courtship and mating dynamics of the smooth newt. Triturus v. vulgaris, was studied using laboratory experiments, an individual-based model, a semi-natural population and a field study. In view of the limitations of laboratory experiments and field observation, the semi-natural and modelling approaches are recommended as additional research tools. In the laboratory, the optimal temperature for spermatophore transfer was just below 13°C, at which point the spermatophore deposition rate is high and oxygen availability not limiting. In the wild females determine the timing of mating. They are highly receptive for a brief period after arrival at the breeding site (early spring), subsequently re-mating only sporadically. Therefore, few courtships take place at mid-season, optimal temperatures. In the semi-natural population. deposition occurred in only 3 - 6% of courtships with a median of one deposition per encounter. Male mating success is therefore unlikely to be constrained by physiological capacity for spermatophore production. Female receptivity and immigration patterns are thus the principle determinants of the operational sex ratio (OSR). According to the model, a male-biased OSR develops rapidly at the start of the season, but the strength of bias will depend on the breeding sex ratio. duration of the arrival period and extent to which males arrive before females. The OSR influences the intensity of competition for mates and the potential for sexual selection. Males compete directly for females by sexual interference, a common but low-gain strategy. Males may also compete indirectly by courting unmated and unfamiliar females preferentially (both of which have a higher probability of being receptive) although more research is needed to establish if males differ in their ability to find receptive females. There is variance in male mating success but the relative contributions of environmental factors and phenotypic traits needs further clarification.