Linking social attention to reproductive state and future reproduction in female monkeys

The demands of complex social life are thought to drive the evolution of cognition in primates. One important approach to testing this hypothesis is to assess if variation in psychological processes impacts an individual’s fitness outcomes, but this can be challenging in primates where field experiments are rare. Here, we examined a naturalistic, semi-free-ranging population of rhesus macaques ( Macaca mulatta ) where routine cognitive experiments are possible. We tracked cognitive performance and annual reproductive outcomes in this seasonally-breeding species, and tested whether attention to and processing of conspecific social information is (1) affected by reproductive status, and (2) associated with individual variation in reproductive success. Across three annual birth seasons, we experimentally measured attention to unfamiliar conspecific face stimuli in N = 103 female monkeys. Reproductive status strongly influenced females’ cognitive performance, as nursing females showed reduced interest in conspecific stimuli compared to those that did not breed. To disentangle current reproductive status effects from relationships between cognition and reproductive outcomes, we then tested whether an individual’s interest in conspecifics was associated with their next-year reproductive success. We found that females that showed greater interest in conspecific faces had a higher likelihood of reproducing in the following year. Our work provides evidence of complex links between sociocognitive performance and reproductive outcomes in monkeys, and highlights how life history stage or physiological state across the life course may also influence the expression of cognitive and behavioural traits.