Saimiri boliviensis 

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Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Cebidae

Scientific Name: Saimiri boliviensis
Species Authority: (I. Geoffroy & de Blainville, 1834)
Infra-specific Taxa Assessed:
Common Name(s):
English Bolivian/peruvian Squirrel Monkey, Bolivian Squirrel Monkey, Black-headed Squirrel Monkey
Spanish Chichilo, Frailecito
Taxonomic Notes: Saimiri taxonomy follows Hershkovitz (1984) and Groves (2001, 2005). An alternative taxonomy is presented by Thorington Jr. (1985) as follows: S. sciureus sciureus (includes the forms albigena, macrodon, and ustus recognized by Hershkovitz, [1984]), S. sciureus boliviensis (includes the forms pluvialis Lönnberg, 1940 and jaburuensis Lönnberg, 1940 recognized by Hershkovitz [1987]), S. sciureus cassiquiarensis, S. sciureus oerstedii (includes the form citrinellus recognized by Hershkovitz [1984]), and S. madeirae (given as a junior synonym of S. ustus by Hershkovitz [1984]). Hernández-Camacho and Defler (1989) recognize S. sciureus caquetensis Allen 1916, given as a junior synonym of S. sciureus macrodon by Hershkovitz (1984). Costello et al. (1993) argued for the recognition of just two species: S. sciureus in South America, and S. oerstedii in Panama and Costa Rica. Boinski and Cropp (1999) using two nuclear genes (IRBP and ZFX) and one mitochondrial (D-Loop) strongly support the Hershkovitz (1984) taxonomy, advocating four distinct species: Saimiri sciureus, S. boliviensis, S. oerstedii and S. ustus.

Hershkovitz (1987, footnote page 22) recognized Saimiri boliviensis jaburuensis Lönnberg, 1940 and S. b. pluvialis Lönnberg, 1940 (given as junior synonyms of S. b. boliviensis in Hershkovitz 1984) as valid subspecies. They are listed by Groves (2001, 2005) as synonyms of S. b. boliviensis.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Wallace, R.B., Cornejo, F. & Rylands, A.B.
Reviewer(s): Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)
This species is listed as Least Concern because it is widespread and abundant, relatively adaptable to habitat degradation, and not subject to high levels of hunting.
Previously published Red List assessments:

Geographic Range [top]

Range Description:According to Hershkovitz (1984) and R. Wallace (pers. comm. 2007), S. b. boliviensis occurs in the upper Amazon, south of the Rio Solimões-Amazonas, between the Rios Juruá and Madeira in the states of Amazonas and Acre, into Bolivia, west of the Rio Negro in northern Santa Cruz Department, in the departments of Pando, Cochabamba, Beni, and Santa Cruz. Wallace et al. (1998) did not find squirrel monkeys in the Noel Kempf Mercado National Park, and indicated that there are no records of this subspecies east of Perseverancia where they surveyed, on the Río Negro, although there are reports of it occurring as far east as the upper Río San Martín. In Peru, Aquino and Encarnación (1994) indicated its occurrence south from the Río Abujao, Department of Ucayali, to Bolivia, and in parts of Huánaco, Pasco, Junín and Cusco. Altitudinal range according to Hershkovitz (1984) is 50 to 500 m above sea level. It is not known which of the two subspecies may occur on the upper Rio Juruá, between the west (left) bank of the Jurua and the Río Ipixuna in Brazil and north of the Río Sheshea to the Rio Abujao in Peru (Hershkovitz 1984; Aquino and Encarnación 1994).

Saimiri boliviensis peruviensis occurs south of the Ríos Amazon and Marañón, between the Rios Huallaga and Ucayali, from the west bank of the Río Tapiche (tributary of the Ucayali), south between the Ríos Pachitea and Tambo (Hershkovitz 1984). Hershkovitz (1984) indicated that the southern limits were unknown, but presumed to be at least as far as the Río Abujao (a west bank affluent of the Río Ucayali). Aquino and Encarnación (1994) indicated the region of the Río Perené, a tributary of the Rio Pachitea. Aquino and Encarnación (1994) reported that is sympatric with Saimiri sciureus macrodon east of the Río Ucayali from about 04ºS southward to the Rio Abujao. In their map, S. b. boliviensis extends across the Rio Blanco to the Río Yavarí. Its occurrence in Brazil to the east of the Rio Javarí has not been documented.
Countries occurrence:
Bolivia, Plurinational States of; Brazil (Acre, Amazonas); Peru
Additional data:
Lower elevation limit (metres):50
Upper elevation limit (metres):500
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The species is common, occurring frequently in large groups of more than 50 animals. Aquino and Encarnación (1994) reported that Saimiri boliviensis was a common species in Peruvian Amazonia. Abundance characteristics are not appreciably different between the two subspecies.

Wallace et al. (2000) recorded primate encounter rates along transects at eight sites in the Rios Blanco y Negro Wildlife Reserve, Santa Cruz, Bolivia. Saimiri boliviensis was seen at two of the sites with an encounter rate of 0.2 and 0.7 groups/10 km, or 4.9 and 9.8 individuals/10 km, respectively. In the Beni Reserve, Painter et al. (1995) recorded an encounter rate of 0.6 groups or 20 individuals/10 km. In the Bosque Chimanes, Rumiz and Herrera (1994) recorded 1.7 groups or 36.4 individuals/10 km. Wallace et al. (1998) did not find squirrel monkeys in the Noel Kempf Mercado National Park where they surveyed (east of the Río San Martín, Santa Cruz Department).

Peres (1997) estimated densities of S. boliviensis boliviensis at várzea (white-water flooded forest) in the Brazilian Amazon: Sacado do Condor 70.7 individuals/km²; Boa Esperança 149.2 individuals/km². They are less abundant in terra firma forest: Porongaba 11.3 individuals/km²; Kaxinawá Reserve: 36.4 individuals/km²; Penedo 19.1 individuals/km²; Altamira 28.7 individuals/km².

Terborgh (1983) estimated a density of 50 individuals/km² in Manu National Park, Peru.
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Typically prefers seasonally inundated forests, river edge forest, floodplain, and secondary forests. They use all levels of the forest, but forage and travel mainly in the lower canopy and understorey. Locomotion involves predominantly quadupredal walking and running.

Squirrel monkeys are small frugivore-insectivores. They spend 75-80% of their day foraging for insects and other small animal prey (Mittermeier and Van Roosmalen 1981; Terborgh 1983; Boinski 1988). During dry season shortages of appropriate fruiting trees they are able to depend entirely on animal prey (Janson and Boinski 1992).

Saimiri groups are multi-male and can be large, up to 100 animals (larger groups are believed to be temporary mergers of two) but most frequently are of 20-75 individuals (Baldwin and Baldwin 1981; Terborgh 1983; Mitchell et al. 1991). As emphasized by Boinski (1999a,b; 2005; Boinski et al. 2005a,b) allthough all squirrel monkeys are morphologicallly very similar, their social systems are quite distinct (summarized in Sussman 2000).

In S. boliviensis, studied by Terborgh (1983) and Mitchell et al. (1991), groups range from 45 to 75 individuals. Females form stable, probably kin-based, coalitions and dominance hierarchy. Females are philopatric (remain in the groups they were born in), while males leave their groups at 4-5 years old, form all-male (bachelor) groups and then disperse into other groups with both sexes. Males are generally unfriendly to each other, and change groups every one or two years. Females commonly show social agression amongst themselves. Adult females are always dominant to males, harass them, and maintain on them on the periphery of the group. Unlike S. oerstedi, males do not show anti-predator vigilance. The fruits they typically exploit occur in large patches of moderate density, and feeding competition is higher than in S. oerstedii, but lower than in S. sciureus.

In S. sciureus, studied in Suriname by Boinski (1999a,b, 2005; Boinski et al. 2005a,b), group sizes range from 15 to 50, and both sexes form a single, linear hiearchy in the group, with most males being dominant to females. Aggression between females is uncommon, but they do not form coalitions. Males form coalitions and can aggressive to each other. Males show vigilance in defense agianst predators. The fruits they exploit typically occur in small but extremely dense patches, and there is considerable feeding competition between group members, much higher than in S. boliviensis.

In S. oerstedii, females do not form dominance hierarchies, and there is no evidence of coalition formation in social interactions. Females transfer between groups before first mating season, and males are philopatric. There is little competition or agonistic interactions between groups, and males show high levels of vigilance for predators. Reproductively mature males collaborate in mobbing females during the mating season. Their fruits they typically exploit occur in small and very scarce patches, and feeding competition is very low.

Mating and births in Saimiri are highly seasonal, seldom exceeding two months in duration. Single offspring. Mating usually occurs during the dry season. In S. oerstedii sexual receptivity in females is synchronized, and lasts only one or two days each season. In S. sciureus, birth synchrony is less pronounced, and the female gives birth occur once a year (Rowe 1996). In S. boliviensis, the interbirth interval is 24 months (Mitchell 1994).

Saimiri boliviensis and S. sciureus frequently form interspecific associations, travelling with Cebus albifrons or Cebus apella (Terborgh 1983; Wallace et al. 2000), benefitting from the disturbance caused by the capuchin monkeys above them, which flushes out insects and small animal prey.

Weight: Adult male 992 g, adult female more than 751 g.

Threats [top]

Major Threat(s): This species is hunted for subsistence use particularly in areas that have already suffered the loss of larger primate species. Habitat loss is also occurring, although not levels that warrant threatened status. Some capture for pets and medical research occurs, notably in Peru.

Conservation Actions [top]

Conservation Actions: This species is listed on CITES Appendix II. It is found in many protected areas.

Saimiri boliviensis boliviensis

Madidi National Park (1,571,500 ha)
Manuripi National Reserve (1,884,000 ha) (in range)
Ríos Blanco y Negro National Reserve (1,423,900 ha) (Wallace et al. 2000)
Beni Biosphere Reserve (135,000 ha) (Painter et al., 1995; Wallace et al. 2000)
Amboro National Park
Carrasco National Park
Isibore-Secure National Park and Indigenous Territory
Pilon Lajas Indigenous Teriitory and Biosphere Reserve

Serra do Divisor National Park (southern part, in range)
Rio Acre Ecological Station (79,418 ha)

Tambopata National Reserve (262,315 ha)
Bahuaja-Sonene Community Reserve (1,091,416 ha)
Manu National Park (1,532,806 ha) (Terborgh 1983; Aquino and Encarnación 1994
Yanachaga-Chemillén National Park (122,000 ha) (Aquino and Encarnación 1994)

Saimiri boliviensis peruviensis

Pacaya Samiria National Reserve (2,080,000 ha) (Hershkovitz 1984; Aquino and Encarnación 1994)

Citation: Wallace, R.B., Cornejo, F. & Rylands, A.B. 2008. Saimiri boliviensis. The IUCN Red List of Threatened Species 2008: e.T41536A10494082. . Downloaded on 22 January 2017.
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