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Marmoset monkey, squirrel monkey or pygmy marmoset

April 18, 2020

Saimiri sciureus and more than 50 species divided into 5 Groups

Marmoset monkeys or squirrel monkeys are common names used to refer to many species of small neotropical primates. Also called pygmy marmosets or pocket monkeys, they can measure between 28 and 45 cm in height (not including the tail) and weigh between 0.55 kg and 1.25 kg. These species are threatened by a series of factors, the most important of which is their illegal commercialization or trafficking as pets, as well as the destruction of their habitat.


Descriptions of marmoset/squirrel monkey species

Since 1807, more than 50 species have been described over the years, many of which have been synonymized. The last revision of the genus (by Van Roosmalen et al., 2002) listed only 26 species.

Subsequently, two more species were described from the Brazilian Amazon, C. bernhardi and C. stephennashi, and four other species have been described recently since then:

  • Callicebus aureipalatii (Wallace et al., 2006), from Bolivia;
  • Callicebus caquetensis (Defler et al., 2010), from the Colombian Amazon;
  • Callicebus vieirai (Gualda-Barros et al., 2012),
  • Callicebus miltoni (Dalponte et al., 2014), from the Brazilian Amazon.

This totals to 32 species, and more are awaiting scientific description (Araújo 2013; Van Roosmalen and Van Roosmalen 2014).

Group division

They are usually divided into five (5) different groups:

Common Squirrel Monkey (Saimiri sciureus)
Diego Delso / CC BY-SA

1. True marmoset monkeys

Saimiri sciureus

The best known species is the common marmoset (Saimiri sciureus) belonging to the Cebidae family. As adults, they measure between 18 and 30 cm in length.

This species is included in Appendix I of the Convention on International Trade in Endangered Species (CITES). The monkey’s preference for secondary forests represents a danger to its conservation. A study conducted in Uganda indicates that in these forests the monkeys are exposed to dramatic habitat decline and anthropogenic activities, and are susceptible to their effects, such as hunting and disease transmission (Chapman 2003).

2. Tamarin monkeys (also called moustached marmosets or pinchés)

White-headed or cottony baby marmoset monkey.
Cotton Top Tamarin (Saguinus oedipus) at Binder Park Zoo in Battle Creek, Michigan
Source: Ltshears, CC BY-SA 3.0, via Wikimedia Commons

The Emperor Tamarin (Saguinus imperator) is a tamarin supposedly named for its similarity to the German Emperor Wilhelm II. The name was initially intended as a joke, but has become the official scientific name. This marmoset lives in the southwestern Amazon basin, eastern Peru, northern Bolivia, and the states of Acre and Amazonas in western Brazil. Emperor Tamarin males and females look alike. Males are the ones that carry babies on their backs. The image is of the female Emperor Tamarin. The image was taken at the San Francisco Zoo.

3. Pygmy marmosets, chichicos, pichicos or bebeleches

Pichico monkey (Saguinus spp.) ( Saguinus fuscicollis and Saguinus graellsi) Slebome CC BY 3.0

4. Lion tamarins (also called golden tamarins)

Leontopithecus rosalia
Mistvan / CC BY-SA

5. Goeldi’s Tamarin Monkey

In addition to its characteristic fur, this species is distinguished from the others, as it still has 3 molars in each hemimandible.

Goeldi’s tamarin, Goeldi’s callimico or Goeldi’s myco ( Callimico goeldii )

Taxonomy according to Linnaeus, 1758

Kingdom: Animalia

Class: Mammalia

Order: Primates

Family: Cebidae

Genre: Saimiri

Species: S. sciureus


The genus Saimiri is a Brazilian word for a small monkey. It comes from saimirím or Çaimbirím, from the Tupi sai, a monkey, and mirím, small, and therefore, “a small monkey” (Tirira, 2008).

Characteristics of marmoset/squirrel monkeys

They differ from other monkey families in having two molars on each side of the upper jaw instead of three, and in having claws instead of nails on all fingers except the thumb.

They are arboreal and their claws allow them to cling perfectly to tree branches.

Marmoset monkeys are small-sized animals, with a soft and silky coat. Many species have tufts of long hair on the ears and cheeks. The body coat is black and white, the head is round, with a black face. In addition, the tail can be as long as the body.

Titi monkey, one of the smallest monkeys in the world.
Marmoset monkey is one of the smallest monkeys in the world. Colombia
Axxis10 / CC BY-SA


Their diet consists mainly of fruits and insects, although some species are omnivorous.

These monkeys feed mainly on five primary types of food: insects, fruits, flowers, nectar and plant exudates (resin, sap and latex) and occasionally these monkeys also feed on bird eggs and animal prey such as small vertebrates, e.g., lizards and bats (Wong et al. 1999).

The monkey acts as an insect controller and its extinction could lead to important changes in insect populations (Solano Rojas, 2007).

Saimiri sciureus / Marmoset monkey
Saimiri sciureus / Brazilian marmoset monkey.
I, Luc Viatour / CC BY-SA

Where does the marmoset monkey live?

They inhabit South America — Colombia, Peru and northern Paraguay, in the dense jungle regions of Brazil and Ecuador in the Amazon River basin.

Most marmoset monkeys are considered endangered species, mainly due to habitat destruction.

It is present in southeastern Colombia, eastern Ecuador, northeastern Peru and western Brazilian Amazon (Rylands and Mittermeier, 2013). In Ecuador it inhabits the Amazon and the eastern foothills (Tirira, 2007). It is also distributed along the Pacific Coast of Costa Rica and Panama from sea level to 500 meters above sea level.


Within the altitudinal range where it moves, the marmoset monkey uses different types of forest, such as primary forest, secondary forest, gallery forests, mangroves and oil palm cultivation (Elais oleifera), with young and mature secondary forest being the most used habitat, especially in the lower and middle strata of the forest (Boinski 1987, Wong 1990, Arauz 1993, Rodríguez-Vargas 2003).

When the availability of food such as arthropods, fruits and flowers is very low in the secondary forests, marmosets use the primary forest to take advantage of the fruits of species that develop in it and as a connection between patches of regenerating forests, or seasonally (Boinski 1986, Wong 1990).

Some authors explain the clear preference for early successional and disturbed habitats compared to primary forest (Janzen and Schoener 1968).


As for reproduction, little is known. In general, the female of fertile age usually gives birth to an annual litter of between one and three young.

The monkey ensures exclusive reproduction of dominant parents (Carroll and Muir, 2002). The dominant pair, who in most groups will be the parents of all other group members, suppresses reproduction in the other adult members. This reproductive suppression of subordinate females in captive callitrichids is a well-described phenomenon (Savage et al., 1988). Despite the usual presence of more than one adult female, reproduction is restricted to a single female per group ( Snowdon and Soini, 1988).

In general, all Saguinus species normally give birth to twins, with single and triplet births not uncommon (Hershkovitz, 1977). Callitrichine twins are dizygotic and share the same placenta and amniotic sac.

During the lactation period, ovulation is not suppressed and estrus occurs 10 days postpartum. The conception rate is high so that some breeding females may be continuously pregnant.

All members of the group are responsible for the care of the offspring (Carroll and Muir, 2002).

Marmoset monkey or black-capped squirrel monkey. Bolivia.
Jens Buurgaard Nielsen/CCbySA

Main threats

Currently the marmoset monkey is on the endangered species list according to the IUCN primate specialist group (IUCN 1996); throughout its range, the main threat faced by the monkey is habitat reduction (Wong et al., 2008).

Habitat loss causes populations to be confined to smaller and smaller patches of forest.

A study carried out in Costa Rica indicates that there is high vulnerability in isolated populations when the available habitat is less than 30 ha and the group size is less than 15 individuals, since this favors the transmission of parasites and the increase of diseases (Boinski and Sirot 1997).

Buying and selling the marmoset monkey as a pet – illegal trafficking

In addition to its restricted geographic distribution, the marmoset/squirrel monkey is an important species in the illegal wildlife trade because it is preferred as a pet (Elizondo, 1999).

The species has an uncertain future, due to the drastic decline in marmoset populations in the 1960s from a yellow fever epidemic, as well as agricultural practices such as the spraying of banana plantations, and tourism development in recent decades. Additionally, they face other threats such as the development of a mosaic of agricultural crops, cattle ranching, human settlements and forest fragments in what used to be mainly forested areas.

The disappearance or isolation of primates can have extreme consequences: their ecological function as seed dispersers and, therefore, their influence on the distribution and composition of trees (March, 2003) can also cause the local extinction of some trees when these primates are lost (Dominy and Duncan 2005).


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