The Peruvian jungle in the upper reaches of the Amazon is home to two different species of monkeys, the Andean titi and the brown-mantled tamarin. What's interesting is that these two species live side by side as if they were members of a single troop. When titis feed on insects, they rely on tamarins to catch them. Meanwhile, tamarins use titis to get Inga beans to eat. To protect against predators, titis keep their eyes aloft looking out for birds of prey, while tamarins keep an eye to the ground for carnivores and large snakes. These species are different in both size and appearance. Why do they coexist? This program attempts to unravel that mystery.