Like humans, some monkeys show declining social activity with age.
Laura Almeling at the German Primate Center in Göttingen, Germany, and her colleagues studied Barbary macaques (Macaca sylvanus; pictured), and found that older females spent less time grooming others and interacted with fewer animals than younger individuals did. These changes were not explained by an overall reduction in social interest, as older males and females maintained an interest in pictures of other animals. Moreover, the monkeys' interest in toys and other non-social objects decreased in early adulthood, mirroring humans' declining eagerness for new experiences with age.
People's tendency to shrink their social circles as they age has previously been attributed to a sense that time is growing short, but the results in monkeys suggest that it may also be rooted in primate evolution, the authors say.
Curr. Biol. http://dx.doi.org/10.1016/j.cub.2016.04.066 (2016)