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The effects of social and ecological stressors on female reproductive success vary among species and, in mammals, previous reviews have identified no clear patterns. However, few studies have focused on both of these relationships simultaneously-the one between social rank and stressors, and the relationships among rank, stressors and reproductive success. We used a longterm data set to study free-living facultatively social yellow-bellied marmots (Marmota flaviventris) to isolate the relationship between female social dominance rank and faecal glucocorticoid metabolites (FGM) levels (our measure of basal stress) in adult females. In addition, we asked whether rank and FGM levels were associated with reproductive success by quantifying the probability of an individual successfully weaning a litter and, for those who did, litter size. High-ranking females had lower FGM levels and larger litters. However, females with the highest FGM levels were significantly more likely to wean a litter. Importantly, body condition (as measured by previous year's August mass)was also positively associated with breeding and with weaning larger litters. Thus, although low-ranking females likely experienced more social stressors than did high-ranking females and adult females often delayed their first reproduction until they were of a sufficient mass, our data suggest that elevated baseline FGM levelsfailed to mediate reproductive suppression. Perhaps, in species like marmots that only have a single chance per year to reproduce, reproductive suppression should be rare. These results highlight the importance of social status, body condition and predator abundance on determining reproductive success in highly seasonal breeders.

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