Squirrel monkey


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Suborder: Haplorrhini
Infraorder: Simiiformes
Family: Cebidae
Subfamily: Saimiriinae
Genus: Saimiri
Species: S. boliviensis, S. oerstedti, S. sciureus, S. ustus, S. vanzolinii
Subspecies: S. b. boliviensis, S. b. peruviensis, S. o. citrinellus, S. o. oerstedti, S. s. albigena, S. s. cassiquiarensis, S. s. macrodon, S. s. sciureus

Other names: S. boliviensis: black-headed squirrel monkey or Bolivian squirrel monkey; macaco de cheiro (Spanish); boliviansk dödskalleapa, boliviansk ekorrapa, or svarthövdad dödskalleapa (Swedish); S. oerstedti: S. oerstedtii or S. oerstedii; black crowned Central American squirrel monkey, Central American squirrel monkey, or red-backed squirrel monkey; panamavsaimiri (Finnish); saimiri à dos roux, singe écureuil à dos rouge, or singe écureuil à dos roux (French); geel doodshoofdaapje (Dutch); gelbes totenkopfäffchen (German); testina di morto (Italian); barizo dorsirrojo, mono ardilla, mono tití, or saimiri dorsirrojo (Spanish); nordlig dödskalleapa, rödryggad dödskalleapa, or rödryggad ekorrapa (Swedish); S. sciureus: common squirrel monkey or South American squirrel monkey; saimiri ecureuil (French); macaco de cheiro (Spanish); ekorrapa gråhövdad dödskalleapa, gråhövdad ekorrapa (Swedish); S. ustus: bare-eared squirrel monkey or golden-backed squirrel monkey; barörad dödskalleapa, nakenörad dödskalleapa, or nakenörad ekorrapa (Swedish); S. vanzolinii: black squirrel monkey, black-headed squirrel monkey, or blackish squirrel monkey; mörk dödskalleapa (Swedish)

Conservation status:  multiple

Life span: 20 years
Total population: 3500 (S. o. oerstedti and S. o. citrinellus), other species unknown
Regions: Costa Rica, Panama, Venezuela, Colombia, French Guiana, Guyana, Suriname, Bolivia, Peru, Brazil
Gestation: 4.8 months (145 days)
Height: 269 to 318 mm (M & F)
Weight: .649 to 1.25 kg (M), .649 to .898 kg (F)

Squirrel monkey in a tree

Until recently, there were only two species of squirrel monkeys, a South American species, S. sciureus and a Central American one, S. oerstedti, but with genetic tools increasingly available, the genus has been reclassified into five species based on genetic, physical, and behavioral characteristics (Groves 2001). Squirrel monkeys are now divided into two groups, the Saimiri sciureus group, containing S. oerstedti subspecies, S. sciureus subspecies, and S. ustus and the Saimiri boliviensis group, containing S. boliviensis subspecies and S. vanzolinii. Most of the literature and information available on squirrel monkeys does not make these newer distinctions and focuses on the traditional taxonomy with only two species (Groves 2001).


Even though there are slight morphological differences among squirrel monkey species, all have the same general facial and body colorations and are easily distinguished as part of the genus. Squirrel monkeys have white masks of fur around their eyes and dark brown or black coloration around the mouth and chin. Species are separated by the shape of the arch of white fur over their eyes, and are either characterized as having a “roman” or “gothic” arch (Rowe 1996; Groves 2001). The species in the Saimiri sciureus group have a “gothic” arch in which the white fur is dramatically high and the darker fur on their heads forms a deep “V” shape between their eyes. S. boliviensis and S. vanzolinii are categorized in the Saimiri boliviensis group and have a “roman” arch of fur which is more rounded than the “gothic” type and does not extend as far up onto the forehead. The gray or black fur on their head makes a very shallow “V” pattern between their eyes (Groves 2001).

Squirrel monkey in a tree

S. oerstedti subspecies are predominantly orange to golden-orange over their backs, hands, feet, and forearms while the crown fur is blackish in females or blackish-brown in males. Their hips and shoulders are grayish-brown and the base of the tail is also this color but is tipped in black (Rowe 1996). They have tufts of fur on their ears and their heads appear very round. S. o. citrinellus are sexually dichromatic with males having gray crown fur and females exhibiting black crowns (Groves 2001). The average height for both male and female S. oerstedti is 270 mm (10.6 in), but males weigh more than females. Average weights in males range from 750 to 950 g (1.65 to 2.1 lb), depending on the time of year, while females weigh between 600 and 790 g (1.32 to 1.74 lb) (Groves 1996; Boinski et al. 2002). The common squirrel monkey, S. sciureus subspecies, has brownish-gray crowns and have less red-orange pelage than S. oerstedti. They are mainly greenish-gray to auburn but S. s. sciureus and S. c. macrodon have orange or yellow hands, feet, and forearms. Differing in the coloration of the forearms and hands from the other subspecies, S. s. albigena exhibits grayish-brown coloration with a very pale orange tinge (Groves 2001). Average weights of S. sciureus range between 554 and 1150 g (1.22 to 2.53 lb) for males and 651 to 1250 g (1.43 to 2.76 lb) for females, with the males measuring only slightly longer than the females at 318 mm (12.5 in) compared to 316 mm (12.4 in) (Rowe 1996). The bare-eared squirrel monkey, S. ustus, stands apart from the other species because of its lack of ear tufts. It is also orange or yellowish on its forearms, hands, and feet with brownish-gray on the head (Groves 2001).

Squirrel monkey in a tree

In addition to having a “roman” arch pattern over their eyes, S. boliviensis and S. vanzolinii have remarkably thin tails compared to members of the Saimiri sciureus group (Groves 2001). S. boliviensis females have gray bodies while males have black bodies. Both sexes have yellow fur on the forearms, hands, and feet (Rowe 1996). Males and females are similar heights, 310 mm (12.2 in) on average, but males are heavier than females, weighing between 963 and 1088 g (2.12 to 2.4 lb), depending on the season while females weigh between 700 and 900 g (1.54 to 1.98) (Rowe 1996). The black squirrel monkey, S. vanzolinii, gets its name from the black band from the crown to the tail. The feet, hands, and forearms are a light yellow (Groves 2001). Height ranges from 275 to 295 mm (10.8 to 11.6 in) in females and 278 to 320 mm (10.9 to 12.6 in) in males, while females weigh significantly less than males, 650 g (1.43 lb) and 950 g (2.09 lb), respectively (Rowe 1996).

Male and female squirrel monkeys are seasonally sexually dimorphic. Male squirrel monkeys have widely fluctuating weights throughout the year and gain weight during the two months prior to the breeding season, taking on a “fatted” appearance from water and fat stored between the muscle and skin on their head, shoulders, upper arms, and ribs. During this period of growth they can gain up to 20% of their body weight and the larger they appear, the more attractive they are to females (Boinski 1987a; Kinzey 1997).

Squirrel monkeys are quadrupedal and move through the forest preferentially traveling on branches between one and two centimeters in diameter (.394 and .787 in). They rarely come to the ground and when they do, it is to forage or play and they are rarely seen leaping horizontal distances greater than two meters (6.56 ft) (Boinski et al. 19981998; Kauffman pers. comm.).


Saimiri boliviensis | Saimiri oerstedti | Saimiri sciureus | Saimiri ustus | Saimiri vanzolinii

Squirrel monkeys are found widely throughout Central and South America. S. boliviensis is distributed throughout Brazil, Bolivia, Colombia, Peru, and Venezuela. S. b. boliviensis is found in Brazil, Peru, and Bolivia while S. b. peruviensis is found in only in Amazonian Peru (Groves 2001; Gold 2004). The Central American squirrel monkey, S. oerstedti, is found in Costa Rica (both subspecies) and Panama (S. o. oerstedti only) and is completely geographically separated from the other species of squirrel monkeys found in South America (Groves 2001). Once long thought to be separated from the other South American species because of introduction into Central America by early humans, molecular data prove that S. oerstedti is, in fact, endemic to this region (Cropp & Boinski 2000). S. sciureus is distributed across several countries: Brazil, Colombia, French Guiana, Guyana, Suriname, and Venezuela. The most restricted in range of the squirrel monkeys is S. vanzolinii which can be found only on the left bank of Lago Mamirauá and at the mouth of the Rio Japura in Brazil (Groves 2001). S. ustus ranges in Brazil south of the Amazon (Groves 2001).

Since 1981, Sue Boinski has studied squirrel monkeys in the wild, focusing her long-term research on S. o. oerstedti in Costa Rica at Corcovado and Manual Antonio National Parks. She has also done comparative research on S. b. boliviensis at Manu National Park in Peru (Kinzey 1997). More recently, Boinski has continued working with squirrel monkeys in a long-term study of S. sciureus in the Central Suriname Nature Preserve in Raleighvallen, Suriname. Most of the literature from field work comes from studies done at one of these four parks, but captive research has supplemented information about wild squirrel monkeys. Saimiri are the second-most used primates in captive research after rhesus macaques (Macaca mulatta) and have been studied widely across a variety of institutions and by a number of researchers (Kinzey 1997).


Squirrel monkeys are found primarily in tropical lowland rainforest throughout the Amazon basin from Paraguay to Guyana and in Costa Rica and Panama. Squirrel monkeys are habitat generalists and have few restrictive requirements in regard to forest type compared to other neotropical primate; they can survive in a myriad of habitat types, including disturbed and edge forests (Kinzey 1997; Kauffman pers. comm.). Across their range, squirrel monkeys are found in similar habitat types ranging from undisturbed tropical and evergreen primary forests, selectively logged tropical forests, secondary growth tropical forests, and disturbed or edge forests (Boinski 1987b; Rowe 1996; Kinzey 1997; Boinski 1999; Boinski et al. 2002). There is marked seasonality in most of these ecosystems, with the dry season lasting from approximately January to March and the rainy season from April to December with coinciding periods of fruit and flower abundance (Boinski 1987b).


Though they are geographically widespread, squirrel monkeys exhibit very little difference in ecological behavior because the habitats in which they are found are quite similar (Boinski 1999; Boinski et al. 2002). Squirrel monkeys are insectivoresfrugivores, consuming insects and fruit in their diet, depending on seasonal abundance of each resource, and supplementing their diets with small vertebrates, nectar, flowers, buds, seeds, leaves, and gum (Boinski & Timm 1985; Kinzey 1997; Boinski 1999). Squirrel monkeys rarely go after insects that are in motion and prefer to capture stationary insects on plant surfaces. They hunt for insects on the surface of live leaves or by unfolding leaf curls of dead foliage and prefer caterpillars and grasshoppers over other insects (Boinski 1988; Janson & Boinski 1992). Saimiri preferentially ingest small, soft, berry-like fruits less than one centimeter in diameter found in the lower and middle canopies of the forest (Janson & Boinski 1992; Kinzey 1997). The small vertebrates consumed include bats, which they systematically search for in large stands of trees, small birds, and bird eggs (Janson & Boinski 1992). During the year, the period of greatest food abundance is between April and June (Boinski 1988).

Squirrel monkey eating

Differences in distribution of available resources across study sites and species leads to different levels of intragroup feeding competition. In Suriname, very small, dense patches of fruit characterize the feeding sites of S. sciureus while in Costa Rica, S. oerstedti forages in fruit patches which are larger but which have few ripe fruits available in each patch. S. boliviensis in Peru forages in the largest fruit patches with the highest densities of fruit in any squirrel monkey study site (Boinski 1999). In Costa Rica, where each fruit tree is depleted quickly by foraging squirrel monkeys, there is little within-group competition for resources because individuals simply move on to another patch after such a short time. In Peru, though, where there is a higher density of available fruit, within-group competition at feeding sites is high as group members have incentive to protect the particular area of the patch in which they are foraging. Among common squirrel monkeys, S. sciureus, within-group feeding competition is intense because fruit is found in small, dense patches easily monopolized by one monkey. The incentive to protect this patch is high and the result is direct feeding competition between members of the group. Between-group aggression is also seen in S. sciureus but not in S. oerstedti or S. boliviensis (Boinski et al. 2002).

Home range sizes and population densities are available for S. oerstedti at Corcovado National Park and for S. boliviensis at Manu National Park in Peru. At Corcovado, squirrel monkeys have home range sizes of about 2 km² (.77 mi²) and the population density is 36 individuals per km² (22 per mi²) compared to Manu where they have home range sizes about 2.5 to 5 km² (.97 to 1.93 mi²) and live in densities of 60 per km² (37 per mi²) (Mitchell et al. 1991). S. sciureus have home ranges between 2.5 and 3 km² (.97 and 1.16 mi²) and live in much lower densities than other species with only 13 individuals per km² (8 per mi²) (Boinski et al. 2002). Squirrel monkeys exhibit similar daily activity patterns, regardless of species, and spend more than half of their day traveling and foraging for insects, while about 11% of their day is spent feeding on fruit and nectar, another 10% of their day is spent resting, and the remainder of their day is spent doing miscellaneous activities such as social behavior and self-grooming (Mitchell et al. 1991).

Their small body size makes squirrel monkeys susceptible to a variety of predators across their range including raptors, snakes, and felids (Mitchell et al. 1991). Raptors are responsible for the highest number of observed predations on squirrel monkeys (Boinski et al. 2002). One predator avoidance pattern seen in squirrel monkeys in Peru is prolonged associations with other primate species. Saimiri and Cebus are seen forming mixed-species groups and associating for many days. These interactions are peaceable and squirrel monkeys benefit from the extensive alarm calling system of Cebus, which serves to alert group members of potential predators (Sussman 2000). Squirrel monkeys may also benefit from maintaining proximity to Cebus in terms of gaining access to previously unexploited resources. Cebus use similar fruit sources and small ranges and squirrel monkeys can exploit Cebus‘ knowledge of these ranges to utilize new fruit patches (Kinzey 1997; Sussman 2000).

Content last modified: March 16, 2006

Written by Kristina Cawthon Lang. Reviewed by Laurie Kauffman.

Cite this page as:
Cawthon Lang KA. 2006 March 16. Primate Factsheets: Squirrel monkey (Saimiri) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/squirrel_monkey/taxon>. Accessed 2020 July 9.


Though Saimiri do not exhibit species differences in ecology, the social structure and behavior of each species varies widely (Boinski 1999). S. oerstedti live in extremely large, multi-male/multi-female groups ranging in size from 40 to 65 animals where there are low levels of aggression and social interactions between males and females are characterized as egalitarian (Boinski 1999). The males within these groups have intense affiliations with one another while the females have low levels of association and social bonding and disperse from their natal groups at sexual maturity (Boinski 1994; Boinski et al. 2005). Males remain in their natal groups and breed with immigrant females. Costa Rican females exhibit no dominance hierarchy within their groups and there is only a slight dominance hierarchy among males. Females may move in and out of several groups over their lifetimes (Boinski 1994; Boinski et al. 2005).

Three squirrel monkeys in a tree

The social organization of S. boliviensis at Manu National Park, Peru is markedly different from that seen in S. oerstedti. In Peru, squirrel monkeys live in multi-male/multi-female groups of 45 to 75 individuals in which males emigrate from their natal groups at sexual maturity and females remain in their natal groups throughout their lives (Mitchell 1994). Both sexes have independent dominance hierarchies, but females within this species are behaviorally dominant over all males within the group. Females often spatially segregate males to the periphery of the group through aggressive interactions, and exhibit aggressive behavior to other females except when interacting with their relatives. Males within the group, on the other hand, are not related but are extremely aggressive towards one another, especially during the mating season when they compete for mates (Mitchell 1994). When males disperse from their natal groups they form all-male bands, or coalitions, in order to immigrate into a new group and begin breeding (Mitchell 1994; Boinski 1999; Boinski et al. 2005). Members of these bachelor groups are usually members of the same age class and they work together to take over the highest positions in their new groups’ dominance hierarchy. These alliances remain strong if the males remain in the same group as is evidenced by cooperative aggression toward immigrating males. Males may move in and out of several groups over their lifetimes (Mitchell 1994).

Among squirrel monkeys of Suriname, social organization is different from both the Peruvian and Costa Rican species. S. sciureus live in much smaller groups than other squirrel monkeys, with only 15 to 30 individuals per group (Boinski 1999; Boinski et al. 2002). These multi-male/multi-female groups are fully integrated, unlike groups of S. boliviensis in which the males are peripheralized by females, and there is a strong dominance hierarchy incorporating both sexes. Aggression is extremely common and Surinamese squirrel monkeys often have disfiguring scars from fighting with group members (Boinski 1999; Boinski et al. 2002). Males are affiliative and form close bonds while females do not appear to have coalitions or other types of social bonds (Boinski 1999). Both male and female S. sciureus emigrate from their natal groups (Boinski et al. 2005). Females transfer between groups several times over their lifetime while males spend much of their lives on the periphery or ranging solitarily. When mixed-sex troops are formed, high-ranking males fight fiercely to prevent solitary or peripheral males from joining the group (Boinski et al. 2005).


Squirrel monkeys have a polygamous mating system, but usually one or two males copulate the most frequently of any in the group (Boinski 1987a). Females reach sexual maturity around 2.5 years of age and males are sexually mature at 3.5 years (Boinski 1987a).

Mother and infant squirrel monkey

Females prefer the sexually mature males that gain the most weight during the two months prior to the breeding season, which lasts from early August to early October. The first signs of “fatting” among males are seen in June (Boinski 1987a). While the largest males monopolize the majority of copulations, young females in their first or second breeding seasons are not as selective as experienced females and will mate with other sexually mature males who may not be as large (Boinski 1987a). In order to determine sexual receptivity, groups of males, usually related because of dispersal patterns among S. oerstedti, chase and grab a female, holding her down to inspect her genitalia. Presumably the males are using olfactory cues to determine her reproductive state because they remain nearby until the female shows interest in the largest males (Boinski 1987a). Gestation lasts 145 days and the birth season lasts from February to early April. This is the dry season and period of highest arthropod abundance (Boinski 1987c). All squirrel monkeys exhibit birth synchrony to decrease chances of predation, though S. oerstedti and S. sciureus exhibit more intense synchrony than S. boliviensis. All of the pregnant females in S. oerstedti groups give birth within two weeks of each other while pregnant S. sciureus females give birth within less than a week. This concentration is much higher than S. boliviensis, who give birth within the same two months (Boinski 1987c; 1999). Most S. oerstedti females give birth every year while S. boliviensis give birth every other year (Kinzey 1997).


Female squirrel monkeys are responsible for almost all infant care. Females within a group exhibit birth synchrony and increased vigilance during the birth season because neonates are particularly susceptible to predation (Boinski 1987c). In S. oerstedti and S. sciureus groups, males also vigorously protect infants from predators, but in S. boliviensis groups, where males are on the periphery of the social group, they exhibit no infant protection (Boinski 1999). For the first month of life, infants remain in constant physical contact with their mother, usually being carried on her back because they are too large and impede movement if they are carried ventrally. During weeks five to seven, infants begin to leave the mother to explore the surrounding environment and interactions between mother and infant become increasingly fewer (Kinzey 1997; Sussman 2000). Infants become independent during the second through fourth months of life, spending more time with peers or play groups. S. oerstedti are weaned by four months of age, but S. boliviensis are not fully weaned until 18 months of age (Sussman 2000). Play is the most common behavior seen in squirrel monkeys younger than one year of age. Associations and relationships made with peers in play groups, especially among males, are thought to carry through to adulthood alliances (Boinski 1999).


Squirrel monkey in a tree

Squirrel monkeys exhibit complex communication behaviors including distinct vocalizations and postural displays. They also use olfactory cues in communication with conspecifics (Kinzey 1997; Sussman 2000). Squirrel monkeys have at least 25 to 30 calls, divided into six groups: “peeps,” “twitters,” “chucks,” “cackles,” “pulsed calls,” and “noisy calls” (Newman 1985). “Peeps” are heard in a variety of contexts including when isolated, during play, while exploring a new environment, during displays, and when disturbed or frustrated. They are tonal vocalizations that do not differ significantly between callers (Newman 1985). “Twitters” are given during feeding, partial isolation, during exploration, and greeting. They are also tonal and differ based on the individual caller. “Chucks” are the most widely used calls among squirrel monkeys and are calls consisting of notes of rapidly descending frequency heard in mother-infant interactions, sexual behavior, and as alarm calls. “Pulsed calls” are used in similar circumstances as “chucks,” but sound like rapidly repeated pulses (Newman 1985). Low in frequency, “cackles” are heard during mild disturbance or agonistic encounters while “noisy calls” are both low and high pitched, nonharmonic shrieks heard during extreme distress (Newman 1985).

One of the most widely recognized postural displays used by squirrel monkeys is also 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 (Baldwin & Baldwin 1981; Boinski 1992). 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 reproductive hormone levels (Boinski 1992). 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 (Boinski 1992). Males use olfactory cues to determine the reproductive status of a female by physically restraining her and inspecting her genitals (Boinski 1987a; 1992).

Content last modified: March 16, 2006

Written by Kristina Cawthon Lang. Reviewed by Laurie Kauffman.

Cite this page as:
Cawthon Lang KA. 2006 March 16. Primate Factsheets: Squirrel monkey (Saimiri) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/squirrel_monkey/behav>. Accessed 2020 July 9.




CITES: Appendix II, Appendix I (S. oerstedti only) (What is CITES?)
IUCN Red List: S. oerstedti, S. vanzolinii: VU; S. ustus: NT; S. boliviensis, S. sciureus: LC (What is Red List?)
Key: VU = Vulnerable, VU = Vulnerable, NT = Near threatened, LC = Least concern, LC = Least concern
(Click on species name to see IUCN Red List entry, including detailed status assessment information.)

Squirrel monkey in a tree

Once thought to exceed 20,000 in number, S. oerstedti is facing serious conservation concerns in Central America. The estimated population of the Panamanian S. o. oerstedti is 2000 individuals while only 1500 S. o. citrinellus are thought to remain (Cropp & Boinski 2000). Unfortunately, there are no population estimates for S. vanzolinii and little published information about its conservation issues and future viability.


Threat: Human-Induced Habitat Loss and Degradation

In Costa Rica, squirrel monkeys are threatened because of increased rates and amounts of deforestation and forest fragmentation and infrastructure for the country’s booming tourism industry. In Panama, they have fared even worse as deforestation has been rampant and virtually unregulated (Boinski & Sirot 1997; Boinski et al. 1998). The development of agribusinesses for oil palm and banana plantations is a serious component of habitat destruction and fragmentation. Squirrel monkeys rarely come to the ground, travel primarily on branches between one and two centimeters in diameter, and will not leap horizontally between trees if the distance is greater than two meters. Logging roads, clearings for telephone and electric power lines, or other practices leading to forest fragmentation restrict populations to smaller areas of forest, decreasing their ability to find food during times of year when food abundance is lowest and leading to a host of genetic diversity issues that could affect their conservation (Boinski et al. 1998).

Fortunately, Costa Rica exhibits among the highest conservation sophistication and largest proportion of protected lands in Central and South America; squirrel monkeys are protected at two reserves, Corcovado and Manuel Antonio National Parks (Cropp & Boinski 2000). Ironically, in protected parks where disturbance such as selective logging, clearing for swidden agriculture, and other sustainable disturbance regimes are prohibited, successional growth of secondary forests has resulted in an abundance of primary forest. This is specifically problematic for squirrel monkeys because they prefer secondary growth forests and will not use primary forests because of the low abundance of arthropods, fruits, and flowers compared to disturbed forests (Boinski et al. 1998).

Potential Solutions

Ecotourism in Costa Rica is focused on the unique fauna and flora of the country and is the largest source of foreign currency revenues (Boinski et al. 1998). Tourism proprietors should be enlisted to assist in conservation strategies revolving around squirrel monkeys in their areas, specifically to develop their operations responsibly with minimal habitat fragmentation.

In protected areas, management should be a focus of the Costa Rican government. In a pristine forest, natural disturbances such as hurricanes and floods would initiate the secondary forest regeneration process. When these types of habitats are not available, in an intact forest, squirrel monkeys would move to another adjacent area that may have secondary forest. Maintaining some areas of secondary successional growth within protected areas, or even better, protecting more adjacent lands surrounding Corcovado and Manuel Antonio would provide more suitable habitat for squirrel monkeys in these areas (Boinski et al. 1998).

Threat: Harvesting (hunting/gathering)

Squirrel monkeys are subject to capture and sale as pets in both domestic and foreign markets. One study revealed that in addition to being easy to obtain and frequently smuggled out of the countries of origin, squirrel monkeys are sold for an alarmingly low price, US$30-50 (Boinski et al. 1998).

Potential Solutions

The trade in squirrel monkeys could potentially be decreased through education programs and alternative income opportunities. Since ecotourism in Costa Rica centers on the unique animal and plant resources in the country, preserving these resources should be a priority to all those who benefit economically from tourism profits. Encouraging tourism operations to staff their outfits with local people will increase the sense of ownership for local populations and will give them direct economic benefit from preserving squirrel monkeys.

Threat: Accidental Mortality

One artifact of development of infrastructure for tourism includes power lines, for both electricity and telephone service. The leading cause of accidental mortality among squirrel monkeys is electrocution as they use power lines to move between patches of forest fragments (Boinski et al. 1998).

Potential Solutions

Better insulation on power lines would decrease the number of accidental deaths by electrocution, but another consideration is that squirrel monkeys use power lines to move between forested areas where natural corridors are not available. In addition to better insulation, maintaining branches that hang over roads and allowing the monkeys to use these to move across roads would increase mobility between fragments as would maintenance of brushy areas below power lines (Boinski et al. 1998).

Threat: Persecution

Where they exist near human settlements practicing small-scale agriculture, squirrel monkeys are occasionally hunted as pests because they often raid and destroy fruit crops, but this persecution is not nearly as serious as other threats facing squirrel monkeys (Boinski et al. 1998).

Potential Solutions

Landowner education about the extreme rarity of these squirrel monkeys might begin to change attitudes towards them and their crop-raiding behaviors, though no work has been done to decrease hunting of squirrel monkeys in this area.

Threat: Pollution

There is little direct evidence of squirrel monkey mortality from pollution, but in forests neighboring oil palm and banana plantations, where pesticides are used liberally, poisoning of squirrel monkeys could potentially be a serious threat to small populations. There have been reports of golden lion tamarins (Leontopithecus rosalia) that died after ingesting insects contaminated with pesticides (Pissinatti et al. 2002).

Threat: Natural Disasters

While hurricanes cause natural disturbances to primary forest that create the secondary growth forest preferred by squirrel monkeys, the hurricane itself can inflict great direct damage to the monkeys. In 1999 a hurricane was likely the responsible for the death of two-thirds of the main troop in Manuel Antonio National Park (Boinski & Sirot 1997).

Threat: Changes in Native Species Dynamics

Nocturnal predation in protected areas with intact predator populations may have an effect on squirrel monkeys. To minimize the chance of predation, squirrel monkeys sleep at the edges of palm fronds and in the case of disturbance, drop to the ground (Boinski & Sirot 1997). By sleeping at the edge of the branches, they decrease the number of predators that can reach them; palm fronds cannot support much weight, so any predator attempting to reach a sleeping squirrel monkey will likely cause disruption and the monkeys will drop to the ground and avoid predation.

Potential Solutions

Wildlife managers could supplement squirrel monkey habitat with sleeping sites that are predator-resistant to decrease the chance of predation and maintain the stability of squirrel monkey populations in some areas (Boinski & Sirot 1997).

Threat: Intrinsic Factors

The limited dispersal options for young, sexually maturing females may have effects on the viability of offspring born to closely related relatives. If females are restricted from emigrating because their natal group is in a forest fragment, the only option is to breed with males that are potentially their relatives (Boinski & Sirot 1997). Inbreeding can lead to a host of problems including inbreeding depression, genetic drift, and low levels of genetic diversity that are potentially serious threats to small populations of squirrel monkeys.

Potential Solutions

It should be a priority to maintain secondary growth forests in protected areas where squirrel monkeys are found in addition to increasing protected areas so that forests are more contiguous rather than fragmented. Corridors connecting habitat fragments may help dispersing females find new groups into which they can assimilate and mate.

Threat: Human Disturbance

One of the serious concerns about S. oerstedti conservation is the hesitancy of officials, especially in Costa Rica, to direct funding towards conservation initiatives because of the common belief that it is an introduced species to the area (Boinski et al. 1998; Cropp & Boinski 2000). With so few funds and a serious conservation crisis in this hotspot of biodiversity, it is politically unpopular to attempt gallant conservation efforts on a species thought to have been introduced by humans before the arrival of European settlers. This is particularly unfortunate because molecular genetic evidence proves the species distinction between S. oerstedti and other squirrel monkeys, and the population of both subspecies is dwindling to critically low numbers (Cropp & Boinski 2000).

Potential Solutions

Changing public attitudes towards squirrel monkeys in Costa Rica will likely engender specialized efforts to conserve this endemic resource. With additional data becoming available to prove their status as non-introduced species, perhaps the process of changing attitudes will quicken and focused conservation activities will become more of a priority for the Costa Rican government and non-governmental organizations.


Captive breeding programs of S. oerstedti are nonexistent in the United States. There are two breeding colonies in Costa Rica that have been maintained through animals seized in the pet trade, but as of 1997, there were only three individuals kept at the Phoenix Zoo (Boinski & Sirot 1997). While other species of squirrel monkeys are well represented in the captive population, problems with hybridization occur because of the changing taxonomic status and inattention to subspecific variation. Furthermore, the founder animals which started the breeding colonies may have been misclassified, making it impossible to differentiate between the species-type of current populations (Schreiber et al. 1998). The taxonomic categorization of captive populations of squirrel monkeys is confusing and not likely to be resolved without genetic testing; nonetheless, animals of questionable taxonomic status can be used in displays at zoos and for educational purposes, regardless of their pedigree.





Content last modified: March 16, 2006

Written by Kristina Cawthon Lang. Reviewed by Laurie Kauffman.

Cite this page as:
Cawthon Lang KA. 2006 March 16. Primate Factsheets: Squirrel monkey (Saimiri) Conservation . <http://pin.primate.wisc.edu/factsheets/entry/squirrel_monkey/cons>. Accessed 2020 July 9.

The following references were used in the writing of this factsheet. To find current references for Saimiri, search PrimateLit.


Baldwin JD, Baldwin JI. 1981. The squirrel monkeys, genus Saimiri. In: Coimbra-Filho AF, Mittermeier RA, editors. Ecology and behavior of neotropical primates, Volume 1. Rio de Janeiro (Brazil): Academia Brasileira de Ciências. p 277-330.

Boinski S. 1987c. Birth synchrony in squirrel monkeys (Saimiri oerstedi): a strategy to reduce neonatal predation. Behav Ecol Sociobiol 21(6): 393-400.

Squirrel monkey artwork

Boinski S. 1987b. Habitat use by squirrel monkeys (Saimiri oerstedi) in Costa Rica. Folia Primatol 49(3-4): 151-67.

Boinski S. 1987a. Mating patterns in squirrel monkeys (Saimiri oerstedi): implications for seasonal sexual dimorphism. Behav Ecol Sociobiol 21(1): 13-21.

Boinski S. 1988. Sex differences in the foraging behavior of squirrel monkeys in a seasonal habitat. Behav Ecol Sociobiol 23(3): 177-86.

Boinski S. 1992. Olfactory communication among Costa Rican squirrel monkeys: a field study. Folia Primatol 59(3): 127-36.

Boinski S. 1994. Affiliation patterns among male Costa Rican squirrel monkeys. Behaviour 130(3-4): 191-209.

Boinski S. 1999. The social organization of squirrel monkeys: implications for ecological models of social evolution. Evol Anthro 8(3): 101-12.

Boinski S, Jack K, Lamarsh C, Coltrane JA. 1998. Squirrel monkeys in Costa Rica: drifting to extinction. Oryx 32(1): 45-58.

Boinski S, Kauffman L, Ehmke E, Schet S, Vreedzaam A. 2005. Dispersal patterns among three species of squirrel monkeys (Saimiri oerstedii, S. boliviensis, and S. sciureus): I. Divergent costs and benefits. Behaviour 142(5): 525-632.

Boinski S, Sirot L. 1997. Uncertain conservation status of squirrel monkeys in Costa Rica, Saimiri oerstedi oerstedi and Saimiri oerstedi citrinellus. Folia Primatol 68(3-5): 181-93.

Boinski S, Sughrui K, Selvaggi L, Quatrone R, Henry M, Cropp S. 2002. An expanded test of the ecological model of primate social evolution: competitive regimes and female bonding in three species of squirrel monkeys (Saimiri oerstedii, S. boliviensis, and S. sciureus). Behaviour 139: 227-61.

Boinski S, Timm RM. 1985. Predation by squirrel monkeys and double-toothed kites on tent-making bats. Am J Primatol 9(2): 121-7.

Cropp S, Boinski S. 2000. The Central American squirrel monkey (Saimiri oerstedii): introduced hybrid or endemic species. Molec Phylogen Evol 16(3): 350-65.

Gold KC. 2004. New World monkeys I: squirrel monkeys and capuchins (Cebidae). In: Kleiman DG, Geist V, McDade MC, editors. Grzimek’s animal life encyclopedia. Volume 14, Mammals III, Second Ed. Farmington Hills (MI): Gale Group. p 101-13.

Groves C. 2001. Primate taxonomy. Washington DC: Smithsonian Inst Pr. 350 p.

Janson CH, Boinski S. 1992. Morphological and behavioral adaptations for foraging in generalist primates: the case of the cebines. Am J Phys Anthro 88(4): 483-98.

Kinzey WG. 1997. Synopsis of New World primates (16 genera). In: Kinzey WG, editor. New world primates: ecology, evolution, and behavior. New York: Aldine de Gruyter. p 169-324.

Mitchell CL. 1994. Migration alliances and coalitions among adult male South American squirrel monkeys (Saimiri Sciureus). Behaviour 130(3-4): 169-90.

Mitchell CL, Boinski S, van Schaik CP. 1991. Competitive regimes and female bonding in two species of squirrel monkeys (Saimiri oerstedi and S. sciureus). Behav Ecol Sociobiol 28(1): 55-60.

Newman JD. 1985. Squirrel monkey communication. In: Rosenblum LA, Coe CL, editors. Handbook of squirrel monkey research. New York: Plenum Pr. p 99-126.

Pissinatti A, Montali RJ, Simon F. 2002. Diseases of lion tamarins. In: Kleiman DG, Rylands AB, editors. Lion tamarins: biology and conservation. Washington DC: Smithsonian Inst Pr. p 255-68.

Rowe N. 1996. The pictorial guide to the living primates. East Hampton (NY): Pogonias Pr. 263 p.

Schreiber A, Wang M, Kaumanns W. 1998. Captive breeding of squirrel monkeys, Saimiri sciureus and Saimiri boliviensis: the problem of hybrid groups. Zoo Biol 17(2): 95-109.

Sussman RW. 2000. Primate ecology and social structure. Volume 2, New world monkeys. Needham Heights (MA): Pearson Custom. 207 p.

Content last modified: March 16, 2006



Photo: Primates in Art & Illustration Collection

Saimiri boliviensis peruviensis
Photo: Rosie Bolen
Saimiri boliviensis peruviensis
Photo: Rosie Bolen

Saimiri oerstedti oerstedti
Photo: Sue Boinski

Saimiri sciureus
Photo: Luiz Claudio Marigo
Saimiri sciureus
Photo: Luiz Claudio Marigo
Saimiri sciureus
Photo: Luiz Claudio Marigo
Saimiri sciureus
Photo: Luiz Claudio Marigo
Saimiri sciureus
Photo: Roy Fontaine
Saimiri sciureus
Photo: Roy Fontaine
Saimiri sciureus
Photo: Roy Fontaine
Saimiri sciureus
Photo: Roy Fontaine

Saimiri vanzolinii
Photo: Luiz Claudio Marigo

Cite this page as: Cawthon Lang KA. 2005 June 13. Primate Factsheets: Orangutan (Pongo) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/orangutan/taxon>. Authored June 13, 2005 by Kristina Cawthon Lang. Reviewed by Simon Husson. Updated June 13, 2005.

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