Infant presence and mother-infant conflict predict fetal loss in wild mandrills

Female fitness depends on reproductive pace and offspring survival, both of which are determined by the ability to balance resource allocation between current and future reproduction. Using 11 years of data on 356 pregnancies (52 of which resulted in fetal loss) from 117 wild female mandrills, we show that females who conceive while still caring for a young infant experience a greater probability of fetal loss as well as increased mother-infant behavioral conflict in the form of maternal rejection. In addition, females whose infants throw more tantrums show a greater probability of fetal loss, consistent with observations from other species where living offspring can interfere in parental reproduction. Finally, females who lose a fetus show greater subsequent reproductive success (produce more surviving infants and show shorter inter-birth intervals) than females who give birth but their infants die soon after birth. These findings suggest that fetal loss may represent an adaptive physiological response to the energetic constraints imposed by overlapping gestation and maternal care, potentially limiting the fitness costs associated with short inter-birth intervals and concurrent investment in multiple dependent offspring.