Population density and temperature influence the return on maternal investment in wild house mice

Abstract

AbstractIn mammals, reproduction is influenced by competitive stress, temperature and food availability and these factors might be crucial already during early life. Favourable early life environment and high maternal investment are expected to improve survival and reproduction. In mammals, maternal investment via lactation predicts offspring growth. As body mass is often associated with fitness consequences, females have the potential to influence offspring fitness through their level of investment, which might interact with effects of population density and temperature. Here, we investigate the relationship between pup body mass at day 13 (used as approximation for weaning mass) and individual reproductive parameters as well as longevity under natural variation in population density and temperatures. Further, we assess the extent to which mothers influence the body mass of their offspring until weaning. We analysed life data of 384 house mice (Mus musculus domesticus) from a free-living wild population that was not food limited. We found a complex effect of population density, temperature and maternal investment on life-history traits related to fitness: Shorter longevity with increasing pup body mass at day 13; delayed reproduction of heavier pups when raised at warmer temperatures; and increased lifetime reproductive success for heavier pups at high densities. House mice could use population density and temperature as cues for predicting future environmental conditions, allowing a mother to adjust her investment according to the environment in which offspring will breed in order to maximise fitness. This study highlights the importance of considering ecological conditions in combination with maternal effects.