Saimiri ustus (I. Geoffroy Saint-Hilaire, 1843)

Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Cebidae, Handbook of the Mammals of the World – Volume 3 Primates, Barcelona: Lynx Edicions, pp. 348-413 : 393-394

4.

Golden-backed Squirrel Monkey

Saimiri ustus

French: Saimiri a dos brilé / German: Nacktohr-Totenkopfaffe / Spanish: Mono ardilla orejudo

Other common names: Bare-eared Squirrel Monkey, Geoffroy's Squirrel Monkey, Short-tailed Squirrel Monkey

Taxonomy. Saimiris wustus 1. Geoffroy Saint-Hilaire, 1843 ,

Brazil, restricted by A. Cabrera in 1958 to the Rio Madeira and restricted further by P. Hershkovitz in 1984 to Humaita, right bank of the Rio Madeira.

Marginally sympatric with S. sciureus in the lower Rio Madeira Basin. S. wustus hybridizes with S. sciureus , and possibly with S. boliviensis . S. ustus has five pairs of acrocentric chromosomes and although Hershkovitz aligned this species with the “Gothic arch” squirrel monkeys (S. sciureus ), cytogenetically it is very similar to the “Roman arch” S. boliviensis . Monotypic.

Distribution. Brazilian Amazon S of the Rio Solimoes-Amazonas in the states of Amazonas, Para, Mato Grosso, and Rondonia, from the Rio Tefé E to the Rio Xingu-Iriri, and S to the upper Rio Guaporé and the headwaters of the Rio Juruena.

Descriptive notes. Head-body 25-35 cm (males) and 23-42 cm (females), tail 40-45 cm (males) and 31-42 cm (females); weight 710-1200 g (males) and 620-880 g (females). The Golden-backed Squirrel Monkey is similar to the Guianan Squirrel Monkey (S. sciureus ), but it is generally larger, with a shorter tail. The back is gold colored, the crown is agouti (intermixed or bordered with black in females), outer sides of thighs are grayish-agouti, and forearms, hands, and feet are orange or yellowish. The face is naked, the ears are only moderately hairy, without tufts, and arches above the eyes are of the Gothic arch type. There is some slight geographic variation in appearance; southerly Golden-backed Squirrel Monkeys have bright orange forearms, whereas over most of their distribution, this color does not extend above the wrists. Those from the lower Rio Tapajos have a yellowish crown and forearms.

Habitat. Lowland evergreen rainforest, including terra firma forest, seasonally inundated forest, and swamp forest. Surveys at Urucu, in the Purus Basin, by C. Peres mainly recorded Golden-backed Squirrel Monkeys in the 100-200m wide, black-water inundated forest (igapo) along river and creek-side forests. When fruit is scarce in the dry season, they become widely vagrant in the terra firma forest.

Food and Feeding. There is no specific information available for this species, but as is typical of all squirrel monkeys, the diet is undoubtedly composed of fruit and small animal prey, particularly orthopterans and lepidopteran caterpillars and pupae.

Breeding. There is no information available for this species.

Activity patterns. The Golden-backed Squirrel Monkey is diurnal and arboreal. Although it has not been studied in the wild, a large part ofits day likely involves moving and foraging in the lower canopy and understory of the forest, searching foliage for small animal prey.

Movements, Home range and Social organization. There is little specific information available for this species, but at Urucu, Peres counted two groups, one of 38 individuals and the other of 76 individuals. Densities were estimated at 0-2 groups/km? and 10-2 ind/km?.

Status and Conservation. CITES Appendix II. Classified as Near Threatened on The IUCN Red List. Very little is known about the Golden-backed Squirrel Monkey in the wild, but its distribution coincides with the so-called arc of deforestation along the agricultural frontier in the south of the states of Para, Mato Grosso and Rondonia, where forests have been clear-cut during the last 20 years for colonization, timber, cattle ranching, and industrial agriculture (notably soy beans). In Brazil, it probably occurs in Amazonia, Juruena, and Pacaas Novos national parks; Abufari, Guaporé and Jaru biological reserves; and Cunia, Iqué, and Samuel ecological stations.

Bibliography. Ayres (1985), Cabrera (1957), Carretero-Pinzén et al. (2009), Groves (2001), Hershkovitz (1984), Peres (1993a, 1994b).

Figures

1. Central American Squirrel Monkey (Saimiri oerstedia), 2. Humboldt’s Squirrel Monkey (Saimiri cassiquiarensis), 3. Ecuadorian Squirrel Monkey (Saimiri macrodon), 4. Golden-backed Squirrel Monkey (Saimiri ustus), 5. Guianan Squirrel Monkey (Saimiri sciureus), 6. Black-capped Squirrel Monkey (Saimiri boliviensis)

Distribution. Brazilian Amazon S of the Rio Solimoes-Amazonas in the states of Amazonas, Para, Mato Grosso, and Rondonia, from the Rio Tefé E to the Rio Xingu-Iriri, and S to the upper Rio Guaporé and the headwaters of the Rio Juruena.