Female mound-building mice prefer males that invest more in building behavior, even when this behavior is not observed

Abstract

Through behavioral correlations, mate choice could influence the evolution of traits that are not directly selected for, or even observed. We addressed whether mound building, a unique collective behavior observed in Mus spicilegus, could be favored by female mate choice, irrespective of whether females were able to observe the behavior. First, we introduced mixed sex groups of wild-born mice in large terraria with building materials and assessed male variation in building investment. Second, we presented females with a choice between males that invested the most versus the least in building. Females were either able to observe the males during building or not. Third, because overwintering juveniles rely on mound protection, we hypothesized that building could be a form of paternal care, and assessed whether males that invested more in building also invested more in direct offspring care. We showed that females were more attracted to males that invested the most in building, even when these behaviors were not observed. In addition, direct offspring care was negatively correlated with males’ investment in building, suggesting that two alternative paternal care strategies (mound building versus direct offspring care) may exist. Our study supports the hypothesis that building could be detectable by phenotypic cues that differ from building behavior per se and that mate choice may influence the evolution and maintenance of mound building that several authors describe as a common good. In the mound-building mouse, individuals gather to build a common mound within which juveniles will spend the winter months. As some males invest more in building than others, we questioned whether females would prefer males that invest more in building behaviors, even though females could not observe males’ building behaviors before mate choice. We assessed male investment in building and conducted choice tests. Females were more attracted to males that invested more in building, even when building was not observed. Hence, building investment seems detectable by phenotypic cues that differ from building behavior per se. Further, the males’ investment in building was negatively correlated with their direct offspring care assessed during retrieval trials. Our findings indicate that two alternative paternal care strategies may exist in this species, and that mate choice might influence the evolution of their remarkable collective building.