Male genitalia are subject to rapid divergent evolution, and sexual selection is believed to be responsible for this pattern of evolutionary divergence. Genital stimulation during copulation is an essential feature of sexual reproduction. In mammals, the male intromittent genitalia induces a cascade of physiological and neurological changes in females that promote pregnancy. Previous studies of the house mouse have shown that the shape of the baculum (penis bone) influences male reproductive success and responds to experimentally imposed variation in sexual selection. Here, we test the hypothesis that the baculum is subject to sexual selection due to a stimulatory function during copulation. We selected male and female house mice (Mus musculus domesticus) from families with breeding values at the extremes of baculum shape and performed two series of experimental matings following which we examined the concentration of Prolactin in the blood of females either 15 (“early”) or 75 (“late”) minutes after ejaculation. Our results provide evidence of a mating-induced release of Prolactin in the female house mouse early after ejaculation, the level of which is dependent on an interaction between the shape of the baculum and male sexual behaviour. Our data thereby provide novel insight into the mechanism(s) of sexual selection acting on the mammalian baculum.

4thGeneration_BaculumLandmarks: TPS file with baculum raw landmarks for each specimen. Landmarks were placed around the periphery of the baculum (36 sliding, 4 fixed) and relative warps (RWs) and centroid size were extracted. Landmark placement conducted using tpsDig 232 developed by Rohlf. Specimen numbers/ID can be matched with ID at the excel spreadsheets (4thGenerationBaculum_Repeatibility_DATA; BaculumShapeVariation_DATA; EarlyGroup_DATA; LateGroup_DATA). 

Experimental_BaculumLandmarks: TPS file with baculum raw landmarks for each specimen. Landmark data from fourth- generation laboratory-reared house mice used for both experimental groups (Early and Late group). Specimen number (ID) can be matched with ID in the excel spreadsheet from ExperimentalBaculum_ShapevariationDATA. 

4thGenerationBaculum_Repeatibility_DATA: Excel spreadsheet containing data used for the analysis of the reliability of baculum landmark placement and repeatability of our measurements.

BaculumShapeVariation_DATA: Excel spreadsheet containing male morphological data and identifiers of each individual for the fourth-generation laboratory-reared house mice. Dataset contains data used to check if 4^th generation house mice aligned with the expected baculum shape extremes.

ExperimentalBaculum_ShapeVariation_DATA: Excel spreadsheet containing the subset of the fourth-generation laboratory-reared house mice used to examine baculum and matinge behaviour effect on female mating-induced Prolactin release (Early and and Late group treatment males). Male identifiers (ID, genetic background extreme and family) and  male body weight are included in the spreadsheet. 

Prolactin_Concentration_AllGroups: Excel spreadsheet containing female identifiers (ID, female genetic background extreme and Family), morphological data (Body weight) and, Prolactin concentration (ng/ml) data. Data used to conduct the statistical analysis to explore whether mating per se had an effect on the levels of circulating Prolactin across the different treatments (Early Group; Late Group; Control Group). Note: Female ID cells in red are individuals that were excluded from the statistical analysis after outlier examination (mean ± 2×sd). 

Mating_Behavioural_DATA: Excel spreadsheet containing male identifiers (ID, genetic background extreme and Family) and mating behavioural data across treatment groups (Early, Late). Data used to conduct the a Principal component analysis (PCA), to reduce copulatory behaviour into fewer axis of variation. 

EarlyGroup_DATA: Excel spreadsheet containing genital shape (RW1, RW2, Centroid size), mating behaviour (PC1) and Prolactin concentration (ng/ml) data and identifiers  of each individual from the Early group treatment (ID, genetic background extreme and family). Data used to conduct the statistical analysis on the Early group experiment. 

LateGroup_DATA: Excel spreadsheet containing genital shape (RW1, RW2, Centroid size), mating behaviour (PC1) and Prolactin concentration (ng/ml) data and identifiers  of each individual from the Early group treatment (ID, genetic background extreme and family). Data used to conduct the statistical analysis on the Late group experiment.