Variation in innovation is maintained by disassortative mating and female choice

Innovative birds are seen as more attractive and often achieve higher mating success.¹^,²^,³^,⁴ Assuming this to be a general phenomenon, selection should promote high levels of innovation that allow birds and other animals to solve novel problems or apply new solutions to old ones.⁵ However, animal populations show substantial variation in this trait, as not all individuals, even in the same population, innovate at the same rate or even innovate at all. It remains unclear which forces of selection maintain these differences. Here, we show that female mate choice and male trade-offs between innovation and competitive ability can maintain this variation in innovation in wild house mice. By combining observational data from semi-natural enclosures with experimental mate choice tests, we found that female wild house mice with different innovative abilities consistently preferred males with opposing skills, with innovative females choosing based on physical size, regardless of innovative ability, and non-innovative females choosing innovative males regardless of size. This disassortative preference in laboratory conditions resulted in disassortative mating under more natural conditions. Males faced a trade-off between innovation and size, a predictor of competitive potential. By taking females' innovation propensity into account, we demonstrate how female preference and male innovation-competition trade-offs create the conditions necessary for sexual selection to maintain variation in innovation.