South and Central America have a variety of monkeys, and depending where you are, and what time of day, you might see one or more species.
In the warmer, tropical areas, you might see an Aotus (Owl monkey), (see photo) the only truly nocturnal primate in northern South America. They spend the day in hollow trees or dense vegetation and emerge at dusk to start feeding. Small, under two pounds, the little owl monkey can adapt to a dangerous situation and become partly diurnal, or awake during the day.
Other monkeys in tropical areas are the titi or tamarin monkeys (Saguinus geoffroyi) and white-faced capuchin monkeys (Cebus capucinus). They've already seen and heard the howler monkeys (Alouatta palliata).
Howler monkeys live in territorial troops, about 15 to 20 individuals of both sexes and all ages. Adult howler males (see photo produce ear-splitting howls that let other troops know where they are--and to stay away. Howlers howl at dawn to advertise their location, a fact that sleeping Castaways might not appreciate.
Male howlers are black but have a fringe of reddish-brown hair that is known as a "mantle." They can weigh around 15 pounds, making them the largest tropical primate. A third smallaer than males, females have a brownish color (see photo of an adult female howler, while infants are a creamy color at birth and darken quickly. The mantle appears when full grown. Howlers are vegetarian, eating leaves and flowers and sometimes fruit.
The Callicebus (Titi) tamarin monkey likes insects and ripe, sweet fruit. Tamarins live in groups of up to five individuals, all ages and both sexes. Tamarin females bear twins, and others in the group assist in monkey-rearing. The Panamanian tamarin, known as the "red-crested" tamarin, weighs only about 1 pound when adult. They have a bright white chest while their arms and neck are red-brown with a tortoise-shell mottling down the back and sides. Their high-pitched call is like a bird call, and they are of the early-to-bed, early-to-rise school of thought.
White-throated capuchin are larger and easier to spot. See this photo of an adult male Cebus capucinus. Adults weigh around 7 pounds and with their white fur, black markings and head "crown" resembling a tonsure, you see why they are named after the Capuchin order of monks. Capuchins are a noisy bunch, living in groups of up to 15, with one male as the "alpha", and as they move about duing the day, they make contiunous screams and twitters that alert others to their presence. They also eat insects and ripe fruit. Their manual dexterity allows them to open and eat nuts. For all their chatter, they are also stealthy, able to move silenty through the trees and drop branches and leaves.