Squirrel monkey
Overview
The squirrel monkeys are the New World monkey
New World monkey
New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...

s of the genus Saimiri. They are the only genus in the subfamily Saimirinae.

Squirrel monkeys live in the tropical forests of Central
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 in the canopy layer. Most species have parapatric or allopatric ranges in the Amazon
Amazon Rainforest
The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...

, while S. oerstedii is found disjunctly
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...

 in Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....

 and Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...

.

Squirrel monkey fur is short and close, colored olive at the shoulders and yellowish orange on its back and extremities.
Encyclopedia
The squirrel monkeys are the New World monkey
New World monkey
New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...

s of the genus Saimiri. They are the only genus in the subfamily Saimirinae.

Squirrel monkeys live in the tropical forests of Central
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 in the canopy layer. Most species have parapatric or allopatric ranges in the Amazon
Amazon Rainforest
The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...

, while S. oerstedii is found disjunctly
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...

 in Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....

 and Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...

.

Squirrel monkey fur is short and close, colored olive at the shoulders and yellowish orange on its back and extremities. Their throat and the ears are white and their mouths are black. The upper part of their head is hairy. This black-and-white face gives them the name "death's head
Totenkopf
The Totenkopf is the German word for the death's head and an old symbol for death or the dead. It consists usually of the skull and the mandible of the human skeleton...

 monkey" in several Germanic languages
Germanic languages
The Germanic languages constitute a sub-branch of the Indo-European language family. The common ancestor of all of the languages in this branch is called Proto-Germanic , which was spoken in approximately the mid-1st millennium BC in Iron Age northern Europe...

 (e.g., German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....

 Totenkopfaffen, Swedish
Swedish language
Swedish is a North Germanic language, spoken by approximately 10 million people, predominantly in Sweden and parts of Finland, especially along its coast and on the Åland islands. It is largely mutually intelligible with Norwegian and Danish...

 
dödskalleapor, Dutch
Dutch language
Dutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...

 
doodshoofdaapjes) and Slovenian (smrtoglavka).

Squirrel monkeys grow to 25 to 35 cm, plus a 35 to 42 cm tail. Male squirrel monkeys weigh 750 to 1100 g. Females weigh 500 to 750 g.

Female squirrel monkeys have a pseudo-penis
Pseudo-penis
A pseudo-penis is a term used of any structure found on an animal that while superficially appearing to be a penis, is derived from a different developmental path.-Mammals:...

 that they use to display dominance over smaller monkeys, in much the same way the male squirrel monkeys display their dominance.

Like most of their New World monkey relatives, squirrel monkeys are diurnal
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...

 and arboreal. Unlike the other New World monkeys, their tail is not used for climbing, but as a kind of "balancing pole" and also as a tool. Their movements in the branches can be very rapid.

They live together in multi-male/multi-female groups with up to 500 members. These large groups can, however occasionally break into smaller troops. They have a number of vocal calls, including warning sounds to protect themselves from large falcon
Falcon
A falcon is any species of raptor in the genus Falco. The genus contains 37 species, widely distributed throughout Europe, Asia, and North America....

s, which are a natural threat to them. Their small body size also makes them susceptible to predators such as snakes and felids. For marking territory, squirrel monkeys rub their tail and their skin with their own urine.

Squirrel monkeys are omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...

s, eating primarily fruits and insects. Occasionally they also eat seeds, leaves, flowers, buds, nuts, eggs and small vertebrates.

The mating of the squirrel monkeys is subject to seasonal influences. Females give birth to young during the rainy season, after a 150- to 170-day gestation. The mothers exclusively care for the young. Saimiri oerstedti are weaned by 4 months of age, while S. boliviensis are not fully weaned until 18 months old. Female squirrel monkeys reach sexual maturity at age 3 years, while males take until age 5. They live to about 15 years old in the wild, and over 20 years in captivity. Menopause in females probably occurs in the mid-teens.

The Common Squirrel Monkey
S. sciureus is captured for the pet trade and for medical research but it is not threatened
Threatened species
Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...

. Two squirrel monkey species are threatened:
S. oerstedti and S. vanzolinii are listed as Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...

 by the IUCN.

Classification

Until 1984, all South American squirrel monkeys were generally considered part of a single widespread species, and many zoologists considered the Central American Squirrel Monkey to be a member of that single species as well. The two main groups currently recognized can be separated by the white above the eyes; it being shaped as a Gothic
Gothic architecture
Gothic architecture is a style of architecture that flourished during the high and late medieval period. It evolved from Romanesque architecture and was succeeded by Renaissance architecture....

 ("pointed") Arch in the S. sciureus group, while it is shaped as a Roman
Roman architecture
Ancient Roman architecture adopted certain aspects of Ancient Greek architecture, creating a new architectural style. The Romans were indebted to their Etruscan neighbors and forefathers who supplied them with a wealth of knowledge essential for future architectural solutions, such as hydraulics...

 ("rounded") Arch in the
S. boliviensis group.
  • Genus Saimiri
    • S. sciureus group
      • Central American Squirrel Monkey
        Central American Squirrel Monkey
        The Central American squirrel monkey is a squirrel monkey species from the Pacific coast of Costa Rica and Panama. It is restricted to the northwestern tip of Panama near the border with Costa Rica, and the central and southern Pacific coast of Costa Rica, primarily in Manuel Antonio and Corcovado...

        , Saimiri oerstedii
        • Black-crowned Central American Squirrel Monkey
          Black-crowned Central American Squirrel Monkey
          The Black-crowned Central American Squirrel Monkey is a subspecies of the Central American Squirrel Monkey. Its range is restricted to the Pacific coast of western Panama to the western portion of the Chiriqui Province and of southern Costa Rica, south of the Rio Grande de Terraba, including the...

          , Saimiri oerstedii oerstedii
        • Grey-crowned Central American Squirrel Monkey
          Grey-crowned Central American Squirrel Monkey
          The Grey-crowned Central American Squirrel Monkey is a subspecies of the Central American Squirrel Monkey. Its range is restricted to the Pacific coast of central Costa Rica. The northern end of its range is the Rio Tulin and the southern end of its range is the Rio Grande de Terraba...

          , Saimiri oerstedii citrinellus
      • Common Squirrel Monkey
        Common Squirrel Monkey
        The common squirrel monkey is a small New World primate from the Cebidae family, and native to the tropical areas of South America.-Location:...

        , Saimiri sciureus
        • Saimiri sciureus sciureus
        • Saimiri sciureus albigena
        • Humboldt's Squirrel Monkey, Saimiri sciureus cassiquiarensis
        • Ecuadorian Squirrel Monkey, Saimiri sciureus macrodon
      • Bare-eared Squirrel Monkey
        Bare-eared Squirrel Monkey
        The bare-eared squirrel monkey is a squirrel monkey endemic to Brazil....

        , Saimiri ustus
    • S. boliviensis group
      • Black-capped Squirrel Monkey
        Black-capped Squirrel Monkey
        The black-capped squirrel monkey is a South American squirrel monkey, found in Bolivia, Brazil and Peru. This South American monkey can be found at the Ellen Trout Zoo.-Subspecies:...

        , Saimiri boliviensis
        • Bolivian Squirrel Monkey, Saimiri boliviensis boliviensis
        • Peruvian Squirrel Monkey, Saimiri boliviensis peruviensis
      • Black Squirrel Monkey
        Black Squirrel Monkey
        The black squirrel monkey , also known as the blackish squirrel monkey or black-headed squirrel monkey, is a small New World primate, endemic to the central Amazon in Brazil...

        , Saimiri vanzolini

Evolution

The crown lineage of the extant squirrel monkeys appears to have diverged around 1.5 million years ago.S. boliviensis appears to be the first diverging species in the group. S. oerstedii and S. s. sciureus, are sister species. S. s. macrodon is the sister species to the S. oerstedii / S. s. sciureus clade.

Color vision

Color vision
Color vision
Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths of the light they reflect, emit, or transmit...

 in squirrel monkeys has been extensively studied as a stand-in for human ailments. In humans, two gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

s for color vision are found on the X chromosome
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...

. Typically, one gene (OPN1LW
OPN1LW
Red-sensitive opsin is a protein that in humans is encoded by the OPN1LW gene.-External links:* -Further reading:...

) produces a pigment that is most sensitive to the 564 nm wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

, while the other gene (OPN1MW
OPN1MW
Green-sensitive opsin is a protein that in humans is encoded by the OPN1MW gene.-External links:* -Further reading:...

) produces pigment most sensitive to 534 nm. In squirrel monkeys, there is only one gene on the X chromosome but it exists in three varieties: one is most sensitive to 538 nm, one to 551 nm, and one to 561 nm. Since males have only one X chromosome, they are dichromatic, although with different sensitivities. Females, on the other hand, have two X chromosomes, so some of them can have copies of two different allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...

s. The three alleles seem to be equally common, leading to one-third of females being dichromatic while two-thirds are trichromatic. Recently, gene therapy
Gene therapy
Gene therapy is the insertion, alteration, or removal of genes within an individual's cells and biological tissues to treat disease. It is a technique for correcting defective genes that are responsible for disease development...

has given the human OPN1LW gene to adult male squirrel monkeys, producing behavior consistent with trichromatic color vision.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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