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Highly differentiated and affiliative social relationships are observed in a variety of mammals, including primates, cetaceans, and social carnivores. Although there has been a transformation in our understanding of the form and function of social bonds in the past two decades, the role of early life social experiences in the development of bonds remains less clear. Few studies have examined whether social relationships during infancy and juvenility (aside from those between mothers and offspring) persist into adulthood. In this study, we used longitudinal data on wild chimpanzees (Pan troglodytes schweinfurthii) at Gombe National Park, Tanzania, to investigate the effects of party-level association during infancy and juvenility (hereafter immaturity) on affiliative relationships among adult males (the philopatric sex). In total, we examined behavioral data from focal follows between 1970 and 2015 (N = 23 adult males). We used maternal associations as proxies for the associations of immature males, and we measured adult male social relationships using party-level associations and grooming activity. We found that immature males that associated with individual adult males at higher rates had stronger relationships with those same adult males later in life. By contrast, rates of association between pairs of immature males did not predict the strength of their dyadic relationships as adults. Overall, these findings emphasize the importance of early socialization in male chimpanzee social development. These results also reinforce studies in mountain gorillas (Gorilla beringei) and bottlenose dolphins (Tursiops sp.), suggesting that the persistence of social relationships that do not involve the mother may be more likely to evolve in long-lived species where young adult males face challenges entering an adult hierarchy composed of stronger and/or more socially experienced competitors. [ABSTRACT FROM AUTHOR]

The mother-offspring relationship is paramount in most mammals and infant survival often depends on maternal investment. In species with prolonged periods of development or co-residence, mothers may continue to influence their offspring's outcomes beyond nutritional independence with benefits biased towards the philopatric sex. Chimpanzees (Pan troglodytes) are long-lived mammals with a protracted period of immaturity during which offspring continue to travel with their mothers. In contrast to most mammals, chimpanzees are also typically male philopatric. Here, we use over 50 years of demographic data from two communities in Gombe National Park, Tanzania, to examine the survival and longevity of both male and female chimpanzees that experienced maternal loss during three different age categories. Males who were orphaned between the ages of 0–4.99 years, 5–9.99 years, and 10–14.99 years all faced significantly lower survival than non-orphans and died earlier than expected. Females faced similarly reduced survival probabilities when orphaned between 0–4.99 and 5–9.99 years of age; however, females who experienced maternal loss between 10 and 14.99 years of age were no more likely to die than non-orphans. Females orphaned in this later age class also lived significantly longer beyond maternal loss than their male counterparts. As observed in other mammals, philopatric male chimpanzees may continue to benefit from their mother's ecological knowledge, whereas maternal influence on female offspring likely fades as they prepare to emigrate. These results emphasize how maternal influence on offspring outcomes can extend well beyond weaning, particularly for the philopatric sex. Significance statement: Mammalian mothers are crucial to their infant's survival and in species where offspring continue to live with their mothers after weaning, maternal influence may extend beyond dependence on mother's milk. While in most group-living mammals females remain in their natal group, chimpanzees typically display the opposite pattern with males residing alongside their mothers into adulthood. Using over 50 years of data on wild chimpanzees, we investigated the consequences of maternal loss both before and after weaning. We found that both males and females orphaned up to 10 years of age were less likely to survive than non-orphans; however, only males orphaned between 10 and 15 years also faced lower survival. These results emphasize how chimpanzee mothers continue to matter for offspring beyond infancy and provide novel data on reduced maternal influence on survival for daughters compared to sons. [ABSTRACT FROM AUTHOR]