Size: Head and Body length; 25-35 cm, tail length; 35-42 cm. Weight; 0.75 – 1.2 kg (females are usually slightly heavier than males).

Habitat and Distribution: They prefer intermediate forest levels of the coastal tropical rainforests of south-eastern Brazil.

Age: 15 - 20 years.

Groups and Breeding: This species lives in huge groups of up to 500 individuals. During the non-mating season these troops often break up into smaller groups based on age, sex, family roles etc. Although females are dominant in troops, they are promiscuous and the fathers play no part in raising their young. Instead, females with no young will often assist a female with young and become a temporary ‘aunt’ for the young. Females will give birth to their young during the peak of the rainy season after a gestation of 150-170 days.

Diet: Mostly fruit and insects but will also eat nuts, eggs, buds and small vertebrates.

• The Squirrel Monkey has the largest brain in proportion to its body of any primate INCLUDING humans!
• Scientists have shown that Squirrel Monkeys can see in colour, and not only that, it appears that males are colour blind compared to females!
• Male Squirrel Monkeys put on up to 20% of their body weight before the breeding season in order to make themselves appear bigger, and therefore more attractive, to females.
• This species is highly vocal and has different calls according to different types of predator. They also rely heavily on other species of primates to alert them to potential predators.
• Female Squirrel Monkeys have a pseudo (pretend) penis to display dominance over smaller monkeys in much the same way as the males do.