Saimiri ustus 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Cebidae

Scientific Name: Saimiri ustus
Species Authority: I. Geoffroy, 1843
Common Name(s):
English Golden-backed Squirrel Monkey, Bare-eared Squirrel Monkey, Golden-backed Squirel Monkey
Spanish Macaco-de-cheiro
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.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): de Oliveira, M.M. de & Boubli, J.-P.
Reviewer(s): Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)
Listed as Near Threatened as past and predicted future declines in the species' population are estimated to be in the region of 20-25% over a 25-year period (three generations) mainly due to the rapid loss of habitat in the southern portion of its range, and the high probability of increased habitat loss in the future due to flooding from hydroelectric projects, highway construction, logging and clear-cutting, and industrialized agriculture (soya and, in the future, biofuel crops). Almost qualifies as threatened under criterion A4c.
Previously published Red List assessments:
2003 Least Concern (LC)
1996 Lower Risk/least concern (LR/lc)

Geographic Range [top]

Range Description: Saimiri ustus occurs south of the Rio Amazonas in Brazil. It has more restricted range than was supposed by Hershkovitz (1984), who placed it east of the Rio Purus south as far as the region of the rios Sepatini and Guaporé, east to the Rios Xingu or Iriri. J. S. Silva Jr. (pers. comm.) believes it extends east of the Rio Purus to the riosTapajós and Juruena, with its range including a belt along the southern margin of the Rio Solimões along the lower reaches of the southern tributaries, including the rios Coarí and Tefé to the east (left bank) of the Rio Juruá. It extends south to the upper reaches of the Rio Guaporé and the headwaters of the Juruena. It is replaced by Saimiri sciureus sciureus just south of the Rio Amazonas, east of the Tapajós, on the Ilha Tupinambarama, east to Parintins.
Countries occurrence:
Brazil (Amazonas, Mato Grosso, Pará, Rondônia)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: There are no published density estimates available.
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). There have been no studies of this species, however, and its ecology is inferred from those of other species.

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 or two days each season. In S. sciureus, birth synchrony is less pronounced and births occur only once every two years.

Amazonian Saimiri frequently form interspecific associations, travelling with Cebus albifrons or Cebus apella (Terborgh 1983; Wallace et al. 2000), benefitting from the disturbance casued by the capuchin monkeys above them which flushes out insects.

Adult male 620-1,200 g (mean 910 g); adult female 710-880 g (mean 795 g) (Jack 2007).
Systems: Terrestrial

Threats [top]

Major Threat(s): Although the species is wide ranging, much of its range in northern Mato Grosso and southern Para is undergoing massive deforestation along the so-called arc of deforestation (the advancing agricultural frontier of logging, cattle, and soy bean).

In the Rio Madeira region, there are several hydroelectric projects that are likely to inundate flooded forests, this species' preferred habitat. Also, in the past 15 years there has been intensive habitat loss in the southern third of this species range due to agriculture and logging activities.

Conservation Actions [top]

Conservation Actions: This species occurs in a number of protected areas, including:

Amazônia National Park (1,114,917 ha)
Pacaás Novos National Park (764,801 ha)
Juruena National Park
Jarú Biological Reserve (353,386 ha)
Guaporé Biological Reserve (618,173 ha)
Iquê Ecological Station (217,184 ha)

It is listed on CITES Appendix II.

Citation: de Oliveira, M.M. de & Boubli, J.-P. 2008. Saimiri ustus. The IUCN Red List of Threatened Species 2008: e.T41538A10494703. . Downloaded on 26 November 2015.
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