Rhesus monkeys make use of their sense of smell to distinguish between members of their own and other social groups, according to new research. The results revealed that monkeys of both sexes inspected the smell of females from other groups longer than the smell of females of the same group, probably because they were more familiar with the odors of individuals belonging to their own social group. Males and older monkeys were more likely to give the odor samples an inspecting lick than females or younger animals, respectively.

Source: Body odor sets female rhesus monkeys apart