Family dynamics reveal that female house mice preferentially breed in their maternal community

Abstract

Whether females breed in their natal group is an important factor in the evolution of extended families in animal sociality. Breeding in natal groups comes with clear costs and benefits, depending on size of the group and presence of older relatives, including mothers. Studying individual decisions about whether to stay or leave can provide insight into the mechanisms and trade-offs governing the formation and structure of family groups. We investigated the family dynamics of a large population of free-ranging commensal house mice. Using dynamic community detection on long term datasets, we determined which females first bred in their natal group. We then looked at how this influenced breeding success. We found most females (77%) exhibited strong philopatry, breeding in their natal groups. Whether a female bred elsewhere was only predictable when natal groups were extremely small and related or large and unrelated. Despite this preference, breeding elsewhere made no difference in how quickly and successfully a female bred. However, presence of their mother did lead females to breed sooner when born during high breeding activity, when competition over reproduction is high. Based on these results, potential loss of fitness does not seem to be the main driver of philopatry in female house mice. The effect of the presence of mothers may indicate retaining prior social connections is an important benefit of breeding in the natal group. Mothers providing benefits also suggests lack of conflict between generations, which is likely an important attribute in the development of extended family groups.Lay summaryWhether animals breed in the group they are born in influences how they form extended family groups. Whether females stay will depend on properties such as presence of older relatives, including mothers. Using long-term wild mouse data, we track groups and which group females bred in. Most stayed, but leaving didn’t reduce breeding success. Presence of mother, who generally stayed, did lead to earlier breeding. This might be a key advantage to remaining to breed.