Effects of maternal social stability on female reproductive success in wild house mice (Mus musculus domesticus)

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Offspring development can be shaped by the maternal environment during gestation and the early postnatal period. Numerous laboratory studies on house mice suggest that social instability induces chronic stress, which can have detrimental effects on infants or shape infant development towards adverse environmental conditions. In contrast, fitness benefits for infants have been reported if females established stable social bonds to same-sex partners through increased weaning success and enhanced offspring quality as indicated by higher weight at weaning. At the same time, intra-sexual competition among females results in reproductive skew and reproductive suppression of group living females. Thus, under natural conditions and in a rather complex social environment it is unclear to what extent daughters benefit from a socially stable (high social stability) or suffer from a socially instable environment (low social stability) of their mothers, and whether such effects are modulated by hormones. The current study will test the hypothesis that a mothers social environment has long-lasting effects on her daughters´ reproductive success in a free-living population of house mice that undergoes seasonal variation in reproductive competition. We will use access to a population of wild house mice that has been carefully studied over the past 14 years. Behavioral data obtained by social network monitoring of the free-living individual house mice will be combined with life history data as well as with long-term steroid hormone profiles obtained by analyzing the hormones incorporated in the animals´ hair. We will use this data set to test three main hypotheses: (I) Maternal social stability during gestation and nursing positively correlates with the lifetime reproductive success of daughters; (II) social instability is a chronically stressful situation for a mother that can influence her daughter´s reproduction success mediated by alterations in steroid hormone output; (III) provided that maternal social instability is associated with elevated glucocorticoid hormone production (stress hormones), we predict modulating effects on their daughters´ physiological hormone profile.