Family legacies: short- and long-term fitness consequences of early-life conditions in female European rabbits.

1. Environmental conditions during an animal's early life can have profound long-term consequences and affect its fitness. In particular, maternal and sibling effects, which can strongly influence the early growth of altricial mammals may be important. Few studies have investigated the influence of such early-life parameters in small mammals, because in these species the early post-natal stage is difficult to monitor under natural conditions. 2. We quantified the effects of litter size (i.e. number of litter siblings), maternal social rank and age and reproductive history of the mother (i.e. whether or not the mother had given birth to a previous litter during this season), and the individual date of birth and social rank on two fitness components of female European rabbits (Oryctolagus cuniculus L.) from a field enclosure population. Analyses were based on data on survival to maturity of 1836 female pups from 10 annual cohorts, and on lifetime reproductive success (LRS; here: the summed up number of offspring surviving to maturity) of 81 adult females from eight annual cohorts. 3. Both fitness components were correlated with the size of the females' original litter and with the age of their mother. Litter size was related to survival to maturity and to LRS in a nonlinear (quadratic) way being highest in females from medium-sized litters. Maternal age also exerted quadratic effects on LRS, which peaked in females born to 2- to 3-year-old mothers. In contrast, survival to maturity increased with increasing age of the mother. 4. Survival to maturity and LRS were decreased in females born later in the breeding season, likely because of the longer time for growth that early born young enjoy before the winter season. In addition, LRS was lower in females which occupied a higher social rank at the onset of their first breeding season. 5. Our results emphasize that factors during early development, in particular parameters of the early social environment, do not only affect juvenile survival but have the potential to exert long-term fitness consequences throughout life.