AI Insight
This study of wild mandrills over 11 years found that female monkeys who conceived while still nursing a young infant had higher rates of fetal loss and showed more maternal rejection behaviors. Females whose infants displayed more tantrum behaviors also experienced increased fetal loss, suggesting that demands from existing offspring can interfere with maintaining a new pregnancy. Importantly, females who lost fetuses showed better long-term reproductive success compared to those whose newborns died shortly after birth, indicating that fetal loss may be an adaptive response to manage the energetic costs of caring for multiple dependent offspring simultaneously.
Why it matters
This research provides evidence that spontaneous pregnancy loss in mammals can serve an adaptive function when resources are limited, helping optimize long-term reproductive success rather than representing pure reproductive failure. The findings contribute to understanding how animals navigate trade-offs between current and future reproduction under energetic constraints.
Understand the Science
by Nikolaos Smit, Berta Roura-Torres, Axelle Delaunay, Alice Baniel, Elise Huchard, Marie J. E. Charpentier
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.
Source: Infant presence and mother-infant conflict predict fetal loss in wild mandrills