The emperor tamarin (Saguinus imperator) is a tiny New World monkey recognized instantly by its long white mustache. Both males and females share this feature, though youngsters begin with short fuzz that lengthens into the full mustache as they mature.

Adults measure about 9 to 10 inches (23 to 26 cm) long, with a tail of 14 to 16 inches (36 to 41 cm), and weigh around 500 grams (1.1 pounds), about the size of a squirrel. Despite their small build, they bound energetically through the canopy of Peru, Bolivia, and western Brazil, sprinting at surprising speeds while living in tight-knit family groups.

The name “emperor tamarin” was first coined in 1907 by Swiss zoologist Emil August Goeldi, who jokingly compared the monkey’s handlebar mustache to that of German Emperor Wilhelm II. The joke stuck and became its official scientific name, Saguinus imperator.

Unlike most primates, emperor tamarins have claw-like nails (tegulae) on all fingers and toes except the big toes, which help them cling to vertical trunks and dash along branches even with a thumb that is not fully opposable. Their long tail provides balance rather than grip, and their light weight allows them to move onto twigs that larger animals cannot use.

Vision adds another edge: about two-thirds of females are trichromatic, able to see a full range of colors and pick out ripe fruit, while all males and the rest of the females are dichromatic with a more limited spectrum.