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Yellow-tailed woolly monkey
Oreonax flavicauda

Conservation status:
Critically endangered

Life span: Unknown
Total population: Unknown
Regions: Peru
Gestation: Unknown
Height: 51.5 to 53.5 cm
Weight: 10 kg

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Suborder: Haplorrhini
Infraorder: Simiiformes
Family: Atelidae
Subfamily: Atelinae
Genus: Oreonax
Species: O. flavicauda

Other names: O. flavicauda: Lagothrix flavicauda, Lagothrix hendeei, Peruvian yellow-tailed woolly monkey, yellow-tailed woolly monkey, Hendee's woolly monkey; hendees uldabe (Danish); geelstaartwolaap (Dutch); harmaavillaapina (Finnish); singe laineux à queue jaune (French); gelbschwanzwollaffe (German); lagotrice a coda gialla (Italian); barrigudo andino, choro cola amarilla, maquisapa chusco (Spanish); gulsvansad ullapa, hendees ullapa (Swedish).

O. flavicauda is monotypic, that is, the only member of the genus Oreonax (Groves 2001; 2005). Groves (2001; 2005) moved the Peruvian yellow-tailed woolly monkey (Oreonax flavicauda) to its own genus (Oreonax) from Lagothrix based on cladistic and morphological grounds. However, the idea of the yellow-tailed woolly monkey in a genus separate from the other woolly monkeys is not a new one and was proposed in the early 20th century on grounds of differences in tooth morphology (Thomas 1927). Some authors disagree with Groves' taxonomic move, and the validity of the genus Oreonax is still debated (Matthews & Rosenberger 2008; Rosenberger & Matthews 2008; Cornejo et al. 2009). For the sake of this factsheet and in recognizance of disagreements over this taxonomic arrangement, Groves (2001; 2005) is followed but the reader is referred to the Lagothrix factsheet for similar species.

As it is among the least known of the primates, data on many aspects of the yellow-tailed woolly monkey behavioral ecology and biology are scarce (Shanee et al. 2007a; Cornejo et al. 2009). Where data is lacking, the reader is referred to the woolly monkey factsheet (Lagothrix sp.) due to presumable similarities between the species.


O. flavicauda
Photo: Noga Shanee

Yellow-tailed woolly monkeys are large and robust, with thick, woolly fur, a hairy face and a prehensile tail with a hairless patch on the underside (Leo Luna 1987; Ramirez 1988; Ankel-Simons 2007). Their fur is somewhat longer and denser than the other woolly monkeys (Lagothrix sp.) (Mittermeier et al. 1977; Aquino & Encarnación 1994). They are deep mahogany or copper, darker towards the upper body and head where it is nearly black, with a whitish patch around the mouth, extending from the chin to between the eyes (Fooden 1963; Mittermeier et al. 1977; Leo Luna 1987; Ramirez 1988). Males are somewhat darker in color than females (DeLuycker 2007). The ends of the extremities are nearly black (Leo Luna 1987). There is some red-auburn coloration on the lower back and tail and the belly has long dark-brown fur (Aquino & Encarnacón 1994). The characteristic feature of the species (and the one which gives the species its name) is the yellowish pelage of the inside end of the last third of the tail (Fooden 1963; Mittermeier et al. 1977; Ramirez 1988; Aquino & Encarnacón 1994). This coloration is not present in infants and juveniles (DeLuycker 2007). Also separating it morphologically from the other woolly monkeys are its prominent and long yellowish pubic hair tuft (more prominent in males) and certain distinctive skull and deciduous dentition characteristics (Thomas 1927; Fooden 1963; Mittermeier et al. 1977; Ramirez 1988; Aquino & Encarnacón 1994).

Several museum specimens had an adult head and body length ranging from 51.5 to 53.5 cm (20.3 to 21.1 in), and the tail was somewhat longer than the head and body length (Mittermeier et al. 1977).

The only body weight figure available for yellow-tailed woolly monkeys is around 10 kg (22.0 lb), and is only a rough, unsexed estimate (Leo Luna 1984 cited in Di Fiore & Campbell 2007; Di Fiore & Campbell 2007). True body weight is likely close to that of the genus Lagothrix (Ramirez 1988).

Woolly monkeys spend almost all of their time in trees, and the tail is used for balance during movement (Ankel-Simons 2007). They can leap as far as 15 m (49.2 ft) (Butchart et al. 1995).


Oreonax flavicauda

The yellow-tailed woolly monkey is the largest primate endemic to Peru. The distribution of the species is both small and fragmented, occurring only in humid montane forests on the northeastern slopes of the Andes Mountains (Butchart et al. 1995; DeLuycker 2007; Shanee et al. 2007a; Cornejo et al. 2009). The species is restricted to the western Amazonas Department and the eastern San Martín Departments of northern Peru, south and east of the Marañón River, as well as past and possible occurrence in restricted areas within the Cajamarca, Huanuco, Loreto and La Libertad Departments (; Graves & O'Neill 1980; Parker & Barkley 1981; Leo Luna 1982a; Aquino & Encarnación 1994; Butchart et al. 1995; review in Shanee et al. 2007a; Shanee et al. 2007a; Cornejo et al. 2009).


O. flavicauda
Photo: Noga Shanee

Yellow-tailed woolly monkeys are only found in primary tropical and subtropical premontane, montane, and montane cloud forests (Graves & O'Neill 1980; Butchart et al. 1995; DeLuycker 2007; Cornejo et al. 2009). It is found between altitudes of 1500 and 2700 meters above sea level and its habitat is generally difficult as it is mountainous, steep, rugged, and foggy with many gorges and ravines (Leo Luna 1980; 1982; DeLuycker 2007; Shanee et al. 2007a; Cornejo et al. 2009). The height of the canopy is usually around 20-25 meters above the ground with thick ground-level vegetation (Shanee et al. 2007a). Within the altitudinal range, there are often a number of microclimates, resulting in a large potential temperature range within which the species lives. For example, at one yellow-tailed woolly monkey habitat at Yambrasbamba, Peru, the temperature ranged from a low of 8˚C (46.4˚F) to a high of 25˚C (77.0˚F) (Leo Luna 1980). There is a somewhat dry season between March and September and a particularly wet season between November and February (Leo Luna 1980; 1982).


Knowledge of the ecology of the yellow-tailed woolly monkey is incomplete (Carnejo et al. 2009). The species is predominantly herbivorous, consuming mostly fruits and flowers, particularly of the genera Cecropia (nettles) and Ficus (figs) (Leo Luna 1980; 1987; DeLuycker 2007). They sometimes eat insects (Leo Luna 1987; DeLuycker 2007). Other recorded dietary items include lichens, leaves, buds, bulbs, epiphyte roots and petioles (Leo Luna 1980; 1987; Butchart et al 1995).

Yellow-tailed woolly monkeys are generally inactive (Leo Luna 1982a).

In lower altitudes, yellow-tailed woolly monkeys may be sympatric with white-bellied spider monkeys (Ateles belzebuth), white-fronted capuchins (Cebus albifrons) and night monkeys (Aotus sp.) (Leo Luna 1987). White-bellied spider monkeys have been seen associating and traveling with yellow-tailed woolly monkeys (Shanee et al. 2007b).

A potential predator is the puma (Felis concolor) and raptors elicit alarm calls (Leo Luna 1980; DeLuycker 2007).

Content last modified: September 30, 2010

Written by Kurt Gron.

Cite this page as:
Gron KJ. 2010 September 30. Primate Factsheets: Yellow-tailed woolly monkey (Oreonax flavicauda) Taxonomy, Morphology, & Ecology . <>. Accessed 2020 April 4.