This image is from the Zurich zoo. Says here the bearded Emperor tamarins live in tropical forests of Brazil, Peru, and Bolivia. They're endangered.
The most fascinating item about these buggers: they have taken to mixing in troops with another kind of monkey, the saddleback tamarin, for the purpose of hunting. The emperors seem to be better at detecting aerial predators, while saddlebacks are better at looking for terrestrial ones. Co-operation in effect. It would be really funny if the saddlebacks had goatees, but no:
So I guess they send these trolls along the ground, while the wise mustachioed monkeys take tree duty. That's good thinking.