Mother’s Age and Social Integration Modulate Sex-biased Maternal Investment in Wild Spider Monkeys (Ateles geoffroyi)

Abstract In many mammal species, mothers are crucial for the survival and development of young offspring. primates, maternal investment may ensure immatures’ also foster their social integration in group, providing long-term fitness benefits. this study, we analysed a wild group (N = 49) male philopatric spider monkeys ( Ateles geoffroyi ). We assessed whether is biased toward sons (compared with daughters) which factors modulate relation. studied 20 mother–offspring dyads, measuring time spent body contact, nursing, carrying, grooming, playing offspring, total 359 focal samples from February to July 2022. then ran generalized linear mixed models assess how these responses varied depending on two-way interactions offspring sex age, centrality. Our results showed that were more likely nurse, carry, have contact younger than older regardless sex. However, found invested female offspring; differences mediated by mothers’ age group. Older mothers, particular, carry daughters, whereas contrary was true mothers. Moreover, socially central be daughters. Overall, our study shows some behaviours sex-biased male-philopatric although experience