Saimiri sciureus live in the neotropical rainforests of South America, except in the southeastern coastal forests of Brazil. However, squirrel monkeys in general (there are 5 different species) are found in Central and South America.
Squirrel monkeys prefer primary and secondary forest, and cultivated areas, usually along streams. They are arboreal and prefer the intermediate forest levels, but will occasionally descend to the ground or in upper canopy levels.
Squirrel monkeys are omnivorous eating mainly fruit and some insects; they also consume some leaves and seeds. The first hour or so of the day is spent foraging for fruit. From then on, they also look for invertebrates and small vertebrates (i.e. small frogs and lizards). A group spreads throughout the forest in all canopy levels to search for food.
Squirrel monkeys live in groups that can number as many as 300 individuals. In the non-breeding season, subgroups form within the main group based on age, sex or family roles. These subgroups are abandoned during the mating season. Group size is affected by habitat. Squirrel monkeys are extremely agile and they often run throughout the forest on branches. Squirrel monkeys display female dominance, with the females forming the central core of the group. Some temporary relationships may form between a mother with no infant and another female’s infant. These older females become “aunts”. Males have a “subadult” period in while they still play with other juveniles. Males also display a clear dominance hierarchy. Males at the top of their hierarchy are not always the most successful in mating; it is unclear what the advantage of social position is.
Squirrel monkeys show no territorial disputes, groups tend to mutually avoid one another. Groups may sometimes be found together, but not for long and perhaps only to search for food. Squirrel monkeys are diurnal (active by day), and activities usually occur along a stream or other water source.
One of the most interesting behaviors of squirrel monkeys is a method of olfactory or chemical communication. In a “urine-washing” display, the monkey, male or female of any age, urinates on its hands and feet and then wipes its hands and feet on its shoulders, arms, and legs, spreading the urine over its body Some functions of “urine-washing” may include marking trails for other members of the group to follow, self-cleaning, displays of dominance, enhanced grasping of branches during locomotion, controlling body temperature through evaporative cooling, or communicating readiness to mate. Other typical chemical communication behaviors seen among squirrel monkeys include rubbing their scent glands of the chest or anogenital area on a substrate or conspecific, rubbing their nose along substrate and subsequently sneezing into their hands, and back rubbing either on surfaces or other squirrel monkeys. Males use olfactory cues to determine the reproductive status of a female by physically restraining her and inspecting her genitals.
Squirrel monkeys are up to 12.5 inches long (body length), with a tail of approximately 16 inches. They have a slender, lithe build, and only weigh about 1.5 to 2.0 lbs (males being slightly larger than females). They are the smallest of the Primate family Cebidae.
Within their own group, squirrel monkeys are promiscuous. Squirrel monkeys are seasonal breeders mating between August and October, with birth between February and April. Gestation lasts 160-170 days after which a single baby is born. The birth season is short and occurs during the time of greatest rainfall, perhaps because the wet season brings an abundance of food and water.
Females prefer the sexually mature males that gain the most weight during a two-month period just prior to the breeding season. The first signs of “fatting” among males are seen in June and the largest males monopolize the majority of copulations.
Males are mature at 4 years of age; females are mature at 2.5 years of age.
Female squirrel monkeys nurse and care for their infants until they are independent. The fathers take no part in raising their young.
Currently, captive squirrel monkey populations are maintained in research labs. Threats to wild squirrel monkeys include eagles in the trees and snakes on the ground. Squirrel monkeys are often kept in captivity, and they were once frequently sold as pets. Habitat destruction, illegal hunting, and capture for the pet trade or medical research all pose threats and problems to squirrel monkey population.
Cawthon Lang KA. 2006 March 16. Primate Factsheets: Squirrel monkey (Saimiri) Behavior. <http://pin.primate.wisc.edu/factsheets/entry/squirrel_monkey/behav>. Accessed 2006 December 9.
Nowak, R.M. 1999. Walker’s Mammals of the World. Baltimore and London, Johns Hopkins University Press.
Rhines, C. 2000. “Saimiri sciureus” (On-line), Animal Diversity Web. Accessed December 09, 2006 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_sciureus.html.