Squirrel monkey

SOCIAL ORGANIZATION AND BEHAVIOR

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).

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).

REPRODUCTION

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).

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).

PARENTAL CARE

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).

COMMUNICATION

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 . . Accessed 2020 July 9.

INTERNATIONAL STATUS

For individual primate species conservation status, please search the IUCN Red List.
Also search the current scientific literature for primate conservation status (overall as well as for individual species), and visit CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora).

Conservation information last updated in 2006 follows, for comparison:

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.

CONSERVATION THREATS & POTENTIAL SOLUTIONS

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.

SPECIAL NOTES

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.

LINKS TO MORE ABOUT CONSERVATION

CONSERVATION INFORMATION

• Saimiri Wildlife
• Saving Mono Titi
• Links for all species

CONSERVATION NEWS

• No current links for Saimiri
• Links for all species

ORGANIZATIONS INVOLVED IN Saimiri CONSERVATION

• Centro de Rescate y Rehabilitación de Primates
• Frisky’s Wildlife and Primate Sanctuary Inc.
• Inti Wara Yassi
• Monkey World – Ape Rescue Center
• Monkeyland Primate Sanctuary
• Primate Paradise
• Sonora Desert Primate Conservancy
• Wildlife Rescue and Rehabilitation Inc.
• Wildlife Waystation

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 . . Accessed 2020 July 9.

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

REFERENCES

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.

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

VIDEO & WEBCAMS

IMAGES

	Saimiri 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