Abstract
Courtship displays are dramatic examples of complex behaviours that vary within and among species. Evolutionary explanations for this diversity rely upon genetic variation, but the heritability of complex phenotypes depends critically on the context in which a phenotype is measured and is seldom investigated in the field. Here, we estimate two measures of heritable variation, repeatability and genomic heritability, in the advertisement songs of wild singing mice. The measures are largely concordant and exhibit an intuitive and striking pattern: we find high repeatability and heritability for spectral characteristics linked to vocal morphology and lower repeatability and heritability for measures of motivation, like song duration and rate. Our results illustrate how advances in genomics and quantitative genetics can be integrated in free-living species to address longstanding challenges in behaviour and evolution.