Squirrel Monkeys

Squirrel Monkeys (New World Monkeys) Squirrel monkeys live in the tropical forests of Central and South America. Their range extends from Costa Rica through central Brazil and Bolivia. Squirrel monkey fur is short and close, coloured olive at the shoulders and yellowish orange on its back and limbs.

Squirrel monkeys throats and ears are white and their mouths are black. The upper part of their head is hairy. This black and white face gives them their German name, ‘skull monkeys’.

Squirrel monkeys grow to 25 to 35 centimetres, plus a 35 to 42 centimetres tail. Squirrel monkeys weigh 750 to 1100 grams. Remarkably, the brain mass to body mass ratio for squirrel monkeys is 1:17 which gives them the largest brain, proportionately, of all the primates. Humans have a 1:35 ratio. Female squirrel monkeys have a pseudo-penis that they use to display dominance over smaller monkeys, much like the way the male squirrel monkeys display their dominance.

Like most of their New World monkey relatives, squirrel monkeys are diurnal and arboreal. Unlike the other New World monkeys, their tail is not used for climbing, but as a kind of ‘balancing pole’ and also as a tool. Their movements in the branches are extremely fast. Squirrel monkeys live together in multi-male/multi-female groups with up to 500 individuals. These large groups can, however, occasionally break into smaller troops.

Squirrel monkeys have a number of vocal calls, including warning sounds to protect themselves from large falcons, which are a natural threat to them. Squirrel monkeys small body size also makes them susceptible to predators such as snakes and big cats. For marking territory, squirrel monkeys rub their tail and their skin with their own urine.

Squirrel monkeys are omnivores, eating primarily fruits and insects. Occasionally they also eat nuts, buds, eggs and small vertebrates.

The mating of the squirrel monkeys is subject to seasonal influences. Females give birth to young during the rainy season, after a 150 – 170 day gestation period. The mothers exclusively care for the young. Squirrel monkeys are weaned by 4 months of age, while other species are not fully weaned until 18 months old. Female squirrel monkeys reach sexual maturity at age 3 years, while males reach sexual maturity around age 5 years. Squirrel monkeys live to about 15 years old in the wild, about 20 years in captivity.

Genus: Saimiri – Bare-eared Squirrel Monkey

The Bare-eared Squirrel Monkey (Saimiri ustus) is a squirrel monkey endemic to Brazil. They have black crowns and reddish backs. The common and Central American species both have hair on the ears, unlike the bare-eared squirrel monkey (S. ustus) of central Brazil. Conservation Status – Least Concern.

Genus: Saimiri – Black Squirrel Monkey

The Black Squirrel Monkey (Saimiri vanzolinii), is a New World monkey from South America. It is found in Brazil, Argentina and Paraguay. The relationship of the Black Squirrel Monkey to other South American Squirrel Monkeys has been the subject of debate. Some researchers have questioned whether the Black Squirrel Monkey is a full species or a regional subspecies. Recent visitors to the area within the range of the Black Squirrel Monkey have reported sightings of Common Squirrel Monkeys (Saimiri sciureus), a closely related Squirrel Monkey species with a much wider distribution. Conservation Status – Vulnerable.

Genus: Saimiri – Black-capped Squirrel Monkey

The Black-capped Squirrel Monkey (Saimiri boliviensis) is a South American squirrel monkey, found in Bolivia, Brazil and Peru. Conservation Status – Least Concern.

Genus: Saimiri – Central American Squirrel Monkey

The Central American Squirrel Monkey (Saimiri oerstedii) is a squirrel monkey species from Central America. It is found in Costa Rica and Panama on the Pacific coast. It has been estimated that the population of the Central American Squirrel Monkey has been reduced from about 200,000 in the 1970’s to less than 5000. This is believed to be largely due to deforestation, hunting and capture for the pet trade.

There are significant efforts within Costa Rica to try to preserve this monkey from extinction. The Central American Squirrel Monkey differs in colouration from squirrel monkeys from South American. While South American squirrel monkeys tend to be primarily greenish in colour, the Central American Squirrel Monkey has a reddish brown back with grey legs and white undersides. There is a black cap at the top of the head and a black tip at the end of the tail. The face is white with black rims around the eyes and black around the nose and mouth. Conservation Status – Endangered.

Genus: Saimiri – Common Squirrel Monkey

The Common Squirrel Monkey (Saimiri sciureus) is a small New World primate from the Cebidae family and native to ten different countries of South America including Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, Venezuela and Puerto Rico.

The Common Squirrel Monkey lives in very large groups, up to 300 individuals, on moist tropical forests and usually forages in the medium and lower levels of the forest and sleeps close to the canopy.

The females are the dominant members of the group. It is a very agile monkey, with a high metabolic rate and although an omnivorous animal, it feeds primarily on insects and other invertebrates. It also feeds on fruits, seeds and other plant parts. It is common to see these squirrel monkeys in mixed groups, moving along with other primate species and birds.

There are four subspecies of Saimiri sciureus:

Saimiri sciureus sciureus
Saimiri sciureus albigena
Humboldt’s Squirrel Monkey, (Saimiri sciureus cassiquiarensis)
Ecuadorian Squirrel Monkey, (Saimiri sciureus macrodon)