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     Squirrel Monkey

Morphology

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).

Habitat

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).

Range 

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).