Infants as Social Magnets: The Influence of Births on Social Interactions in Redfronted Lemurs (Eulemur rufifrons)

Infant survival is an important component of parental fitness in iteroparous species with slow life histories. From the infant's perspective, survival can be more or less directly influenced by the social environment, with group members potentially representing either a threat or a buffer against external stressors. Therefore, studying social relationship patterns during early development may provide insights into the effect of social factors on infant survival. To understand how group members interact with infants, and whether social relationships change due to the presence of infants, we conducted focal behavioral observations on four groups of wild redfronted lemurs (Eulemur rufifrons) during the birth season. Infant handling consisted mostly of grooming, while aggressive infant handling behaviors and allomaternal care occurred very rarely. Infants were groomed by individuals of all age-sex classes at similar rates except for a trend of higher infant handling rates in juvenile females. After giving birth, mothers received more approaches and were closer in proximity to other group members than before birth, but there were no changes in grooming rates of mothers and other group members. Mothers also initiated more aggressive interactions towards other group members after giving birth. Therefore, other redfronted lemurs were clearly attracted to infants, which caused changes in affinitive relationships of mothers. At the same time, the increase in maternal aggression indicates that group members also represent some threat to infants. Our study provides a starting point for future studies, exploring how these early infant handling interactions and the mother's relationships impact an infant's subsequent survival, development and future relationships.