Competitor size, male mating success and mate choice in eastern mosquitofish, Gambusia holbrooki

► Males might increase mating success by choosing a favourable social environment. ► We tested if competitor size and sex ratio affect male mate choice in mosquitofish. ► Males associated equally with large and small-male groups when females were present. ► Males associated more with large than small-male groups when females were absent. ► Do benefits of large associates balance higher mating success in small-male groups?