Golden Lion Tamarin- They actually let them roam free outside among a small wooded area. Each Tamarin has a radio collar in case they decide to leave the area. Golden Lion Tamarins are very territorial, so they have not had any attempt to escape yet.
The Golden Lion Tamarin (Leontopithecus rosalia, Portuguese: Mico-leão Dourado) also known as Golden Marmoset, is a small New World monkey of the family Cebidae. Native to the Atlantic coastal forests of Brazil, the Golden Lion Tamarin is an endangered species and among the rarest animals in the world, with an estimated wild population of "more than 1,000 individuals" and a captive population maintained at approximately 490 individuals.