The effect of sex ratio on male mating tactics and female fitness in Rana sylvatica breeding aggregations

Background/Question/Methods

Females can obtain direct or indirect benefits by choosing high-quality mates. There are many systems, however, where intense male-male competition prevents females from choosing mates, and males do not provide direct benefits. Nevertheless, male competition may indirectly benefit females, as only high-quality males should be able to win contests. Little work has examined this potential indirect effect of male competition. We used a two-pronged approach to address how the sex ratio and male competition affects wood frog (Rana sylvatica) females. First, we examined whether male traits correlated with amplexus (pre-mating) success were more strongly selected as competition increases. Second, we examined female fitness in high versus no male competition mating environments. 

Results/Conclusions

We found that males that minimized stationary searching and engaged in energetically costly behavior were more likely to amplex during intense competition. We used total offspring production as well as tadpole survivorship, competitive ability, and growth rate as proxies of female fitness, and we will discuss these results. Our findings suggest that male competition may help to ensure that females mate with high-quality males.