Toward independence: maternal social status and experience shape mother–infant relationships in mandrills

Abstract Mammalian species with slow life histories invest heavily in offspring care to meet offspring nutritional and developmental requirements, typically at significant costs to mothers. While maternal care has been extensively studied, understanding the mechanisms driving variation in mother‒offspring relationships during key offspring developmental periods require more comparative data from natural populations. Using eight years of behavioral data, we analyzed mother-offspring interactions in 68 infants born to 46 mothers in wild mandrills ( Mandrillus sphinx ), spanning multiple birth cohorts and the entire first year of infant life, a critical period for individual social and physical development. We found that mothers dynamically adjusted caregiving behavior as infants aged, reducing physical contact while promoting spatial independence and social integration. Maternal traits, such as age, social rank, and reproductive history, shaped maternal phenotypes: high-ranking mothers promoted infant socialization while reducing carrying, and older, multiparous mothers invested more in grooming and physical contact than younger, inexperienced females. Previous infant loss predicted reduced maternal aggression, potentially due to fewer immatures to care for or behavioral adjustments aimed at improving offspring survival. Finally, mothers fostered closer bonds with their daughters while encouraging their sons’ independence, possibly resulting in more frequent tantrums observed in males. This sex-biased pattern likely reflects preparation for contrasting life histories between the sexes in this species. By combining extensive longitudinal observations with fine-scale, individual analyses, our study emphasizes the dynamic and multifaceted nature of early mother-offspring interactions and their evolutionary implications in long-lived mammals.