Pithecia monachusmonk saki

Geographic Range

Also known as Pithecia hirsuta, Pithecia monachus can be found in northwestern Brazil, Colombia, Ecuador and Peru (Nowak, 1999). Members of this species occur in the Colombian trapezius north of the Amazon, and extend from north of the Putumayo River to the southern bank of the Yari, Caqueta and Orinoco rivers. The range of Pithecia monachus is limited to the upper elevations of well-developed rain forests of these regions (Hernandez-Camacho and Cooper, 1976). (Hernandez-Camacho and Cooper, 1976; Nowak, 1999)


Arboreal, high canopy dwellers. They are very nervous around humans and disturbance, thus very little data has surfaced on the lifestyle of P. monacha. However, scientists agree that the tallest trees available (from 10-35 meters tall) are the habitat of choice for these animals, and in most instances they are the sole primate inhabiting this niche. (Moynihan, 1976)

Physical Description

Sakis are characterized by their small size of 30-50 cm and very heavy, thick and nonprehensile tail which adds 25-55 cm to their body length (Nowak, 1999). The face of the monk saki is partly bald but bearded with a hood of curly black hair covering the forehead. The nostrils are laterally positioned on the face (Flannery 2004). Sakis are generally black, but their hands and feet are light in color.

The skull morphology is distinctive: the orbits are separated from the brain case by a frontal depression. The incisors are forward-facing, long canines are present and used to break the hard skin of fruits. They have quadritubercular molars with deep basins (Seth & Seth, 1986).

The hands are similar to those of Aloutta spp. in that they exhibit a split between the second and third digits (Moynihan, 1976). Each digit has a nail, and the front limbs are shaped for gripping branches after a leap. The hind legs are modified for fast and far leaping. Vision is stereoscopic for an arboreal habitat. (Flannery, 2004; Moynihan, 1976; Nowak, 1999; Seth and Seth, 1986)

  • Range mass
    1 to 2 kg
    2.20 to 4.41 lb
  • Range length
    30 to 50 cm
    11.81 to 19.69 in


Adult, monogamous pairs breed for life.

Pairs raise a maximum of a single offspring per breeding season. Monk sakis typically retain a family group size of 4.5 individuals on average. Females are in estrus for approximately 18 days, and after conception members of this genus gestate for approximately 170 days (Nowak, 1999).

  • Average number of offspring
  • Average number of offspring
  • Average gestation period
    170 days

Young cling to female's belly when young, and then move to her back as they approach weaning age (Britannica, 1981).

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female
  • extended period of juvenile learning



All species of Pithecia are diurnal. The monk sakis are quadrupedal leapers. They are skittish and shy. Family groups are nuclear families consisting of a monogamous pair with its offspring. These families raise offspring in defended territories, similar to gibbons in the genus Hylobates. A peculiar behavior is observed at night when several families sleep in the same tree. The adults recognize their mate by highly specialized vocalizations; acoustic signals including squeaks, whistles and trills are used for low intensity aggression. Barks and grunts constitute a higher level of aggression, and finally, roars are the most extreme aggressive vocalizations. The monk sakis practice extensive allogrooming as a general social behavior which is nonsexual in orientation or motivation. (Hernandez-Camacho and Cooper, 1976; Moynihan, 1976)

  • Range territory size
    0.33 to 0.5 km^2

Home Range

Home range differs by gender: males travel in a 50 ha area, while the females utilze only 33.5 ha. (Dunbar, 1988)

Communication and Perception

Food Habits

The diet of the monk saki is frugivorous but also includes seeds, nuts, and some insect material. They have also been documented to prey on bats (Moynihan, 1976; Hershkovitz, 1977). They use their large canines to break their food before ingesting it. The monk saki's high quality diet restricts their range in that they must be able to sequester enough high-protein food for their immediate family group (Terborgh, 1983). (Hershkovitz, 1981; Moynihan, 1976; Terborgh, 1983)

  • Animal Foods
  • mammals
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit

Conservation Status

This species is rated "Least Concern" by the IUCN, as there are still believed to be substantial populuations in the upper Amazon basin. It is listed on Appendix II of CITES, so there are restrictions on international trade of the animals or their parts.

Other Comments

Very little research has been done on Pithecia monacha, perhaps for two reasons: they do not survive well in captivity, and are very difficult to view in the wild, due to shyness and a very high habitat.


Tara Poloskey (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.



living in the southern part of the New World. In other words, Central and South America.

World Map


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate

  1. active during the day, 2. lasting for one day.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


an animal that mainly eats fruit


An animal that eats mainly plants or parts of plants.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.


specialized for leaping or bounding locomotion; jumps or hops.


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


"CITES" (On-line). Accessed October 14, 1999 at http://www.cites.org/.

1981. Saki. The New Encyclopedia Britannica, Vol. 10.

Dunbar, R. 1988. Primate Social Systems. Ithaca, New York: Comstock Publishing Associates.

Flannery, S. 2004. "Monk Saki (Pithecia monachus)" (On-line). Primate Behavior. Accessed November 03, 2004 at http://members.tripod.com/uakari/pithecia_monachus.html.

Hernandez-Camacho, J., R. Cooper. 1976. The Nonhuman Primates of Colombia. Pp. 35-69 in R Thorington, Jr., P Heltne, eds. Neotropical Primates. Washington D.C.: National Academy of Sciences.

Hershkovitz, P. 1981. Living New World Monkeys(Platyrrhini)-With an Introduction to Primates: Volume 1. Chicago and London: The University of Chicago Press.

Moynihan, M. 1976. The New World Primates. New Jersey: Princeton University Press.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore, Maryland: Johns Hopkins University Press.

Seth, P., S. Seth. 1986. The Primates. New Delhi/Allahabad: Northern Book Centre.

Terborgh, J. 1983. Five New World Primates: A Study in Comparative Ecology. New Jersey: Princeton University Press.