Maternal lactational investment is higher for sons in chimpanzees

Abstract Maternal lactational investment can affect female reproductive rates and offspring survival in mammals be biased towards infants of one sex. We compared estimates lactation effort among mothers, assessed as their potential milk contribution to age-specific infant diets (mother-infant differences fecal stable nitrogen isotopes, δ 15 N), the timing weaning (infant age at last nursing bout) maternal inter-birth interval lengths for male chimpanzees ( Pan troglodytes ) Ngogo, Uganda. Infant males had greater proportions diets, indicated by higher mother-infant N (Generalized Estimating Equation, GEE: p < 0.01). This may mean that mothers sons showed than daughters. stopped older ages females (Kaplan–Meier product limit estimate, Breslow estimator: 0.05). Mothers longer interbirth intervals daughters (GEE: All three measures was sons. Male cost more ensure because are vulnerable and/or genetic returns on daughters, philopatry means chimpanzee have influence success Chimpanzee trade off growth-related benefits high against reduced rates. Significance statement via affects investigated variation wild relation sex using proxies investment: a physiological biomarker provide an estimate effort; observations nursing, which we used establish ages; between births surviving infants. toward all indicators fecundity due These results would expected if leads better condition later life, thus inclusive fitness mothers.