Supplemental data for: Finding Mr. Right: Housing quality affects male mouse attractiveness to females, with implications for conservation captive breeding

Females generally prefer mates with traits indicating low stress (e.g. large size; good health). In captivity, stress from suboptimal housing might therefore reduce male attractiveness. We tested this hypothesis using mice (Mus musculus), predicting that compared to males conventionally-housed (CH) in small lab cages, females will preferentially court higher welfare males from well-resourced (WR) ‘enriched’ conditions. First, a small-scale pilot opportunistically used 12 DBA/2 males and 22 DBA/2 females, both sexes differentially-raised (half CH, half WR), but with heterogeneous reproductive experience. In T-maze mate choice tests, CH females preferred males from WR housing, spending significantly more time near and sniffing them. Next, the main study used 12 dyads of DBA/2 male litter-mates, differentially-raised from 4 to 12 weeks old. Twelve virgin oestrous DBA/2 female sister pairs were each presented with a dyad of differentially-raised virgin brothers. Choice behaviour was videoed, and analyzed blind to housing. Ultrasonic recording confirmed courtship singing in all trials. Females spent on average 1.5 times longer near males from WR housing than their CH brothers, sniffing them for nearly twice as long: a significant preference that did not vary with female housing. Effects were not explained by male body weight, testis weight or anogenital distance. Overall, as predicted, WR housing rendered males more attractive. When subsequently housed for mating in male-sister-pair trios, 6 WR and 6 CH, WR trios also tended to be more likely to have litters. For species with problematic breeding programmes, improving welfare via higher-quality housing may therefore help improve reproductive success.