Uakari
Cacajao sp.

TAXONOMY

Suborder: Haplorrhini
Infraorder: Simiiformes
Family: Pitheciidae
Subfamily: Pitheciinae
Genus: Cacajao
Species: calvus, melanocephalus
Subspecies: C. c. calvus, C. c. novaesi, C. c. rubicundus, C. c. ucayalii, C. m. melanocephalus, C. m. ouakary

Other names: uacari; C. calvus: bald uakari, bald-headed uacari, red uakari, red-and-white uacari; witte oeakari (Dutch); ouakari chauve (French); cacajao, cacayao, huapo colorado, huapo rojo, uacaries, uacari blanco (Spanish); skallig kortsvansaparöd uakari, skallig uakari, vit uakari (Swedish); C. c. novaesi: Novaes' bald-headed uacari; uacarí (Spanish); C. c. rubicundus: red bald-headed uacari; mono ingles, uacarí-vermelho (Spanish); C. c. ucayalii: Ucayali bald-headed uacari, Peruvian red uacari; C. melanocephalus: black uacari, black-headed uacari, Humboldt's black-headed uacari; zwartkopoeakari (Dutch); ouakara à tête noire (French); mono chucuto, uacari-bicó, uacarí-preto (Spanish); svart uakari, svartansiktad kortsvansapa, svarthuvad uakari (Swedish).

While some authors list several additional subspecies of uakari, as per Groves (2005), only four subspecies of C. calvus are considered here. C. melanocephalus is sometimes divided into two subspecies, C. m. melanocephalus and C. m. ouakary, and here both are considered at the subspecific level as per Hershkovitz (1987) for the sake of simplicity. Some authors also elevate the two subspecies of C. melanocephalus to full species level, however here they are not treated as such. In 2008, two additional species of uakari, C. ayresi (Aracá uakari) and C. hosomi (Neblina uakari) were described (Boubli et al. 2008). The common and generic names of the uakari species likely have their origin in indigenous Amazonian languages (Barnett 2004).

MORPHOLOGY

Cacajao calvus rubicundus
Photo: Roy Fontaine

Medium-sized uakaris are the largest of the New World monkeys without a prehensile tail and are characterized by the presence of a short and bushy tail which is less than half to only one third of the head and body length of the animal (Fontaine 1981; Hershkovitz 1987; da Cunha & Barnett 1989; Barnett 2005; Norconk 2007). The muzzle is broad (Hershkovitz 1987). The main distinguishing characteristics between the two species of uakari are the head and the pelage. The C. calvus head ranges from bald to sparsely haired, while C. melanocephalus has plenty of hair (Barnett 2005). The profound lack or near lack of pigment in the face and head of C. calvus results in a reddish appearance of the face and head caused by the presence blood vessels near the surface of the skin (Hershkovitz 1987; Barnett 2005). The face of C. melanocephalus is black, and the head has blackish hair (Hershkovitz 1987; Barnett 2005). The pelage of C. melanocephalus is generally a rich and bright reddish-brown, with black head, neck, hands, and feet, while C. calvus can range among subspecies from reddish to orange and buffy to whitish or pale yellow (Hershkovitz 1987; Barnett 2005; A. Barnett pers. comm). C. m. ouakary has a gold-colored cape and C. m. melanocephalus has a black one (A. Barnett pers. comm.). The color differences between populations can be arranged on a geographic continuum; that is, they grade from one to another by location (Barnett 2005). This is well exhibited in C. calvus, where C. c. calvus is very pale, while C. c. novaesi is orange-buff, C. c. rubicundus is reddish, and C. c. ucayalii is reddish-orange (Hershkovitz 1987; Barnett & Brandon-Jones 1997).

Cacajao melanocephalus
Photo: Luiz Claudio Marigo

The ventrum is nearly bare (Barnett 2005). Both sexes have a sternal gland which might be involved in olfactory communication (Fontaine & DuMond 1977). In both species, the fur on the shoulders and anterior back is long, shortening by the midback, and in C. melanocephalus, the hair on the sides of the body can be up to 10 cm (3.9 in) long (Hershkovitz 1987; Barnett 2005). In general, in both species, males are larger and weigh more than the females but there are no differences in the pelage between males and females (Hershkovitz 1987; Barnett & Brandon-Jones 1997).

C. melanocephalus head and body lengths average 41.4 cm (16.3 in) (male) and 38.9 cm (15.3 in) (female), while C. calvus average 45.6 cm (18.0 in) (male) and 44.0 cm (17.3 in) (female) (Hershkovitz 1987). Based on very small samples, male C. melanocephalus can weigh between 2.66 kg and 2.8 kg (5.9 and 6.2 lb), while C. calvus of both sexes can weigh between 2.75 and 3.45 kg (6.1 and 7.6 lb) (Ayres 1986 cited in Hershkovitz 1987).

Uakaris are predominantly arboreal quadrupeds, most frequently walking, running, clamber-running, leaping and bridging in the upper and middle-upper levels of the forest canopy (Walker 1996; Walker & Ayres 1996; Boubli 1997a; Barnett 2005). Less frequently, arm-swinging is used, and on rare occasions, bipedal movement is seen (Boubli 1997a). In addition, uakaris will often leap or drop between supports during travel, a result of their relatively discontinuous forest habitat (Walker 1996; Walker & Ayres 1996; Boubli 1997a). While feeding, uakaris usually sit and while resting they will either sit or lie on their belly (Walker 1996). Uakaris are capable of swimming (Barnett 2008). Uakaris seasonally forage on the ground (Ayres 1986; Barnett 2008).

In captivity, uakaris have lived into their mid-thirties (Weigl 2005).

RANGE

Generally, uakaris are found in neotropical Amazonia, including Brazil, Colombia, Peru, and Venezuela (Hershkovitz 1987; Boubli 1997a). Between the species, C. melanocephalus is found in the Rio Negro basin area in the Amazon region in far northwest Brazil, eastern Colombia and southern Venezuela (Boubli 1993; 1997; Barnett 2005). C. calvus and its subspecies are only found in Brazil and Peru but may have been present in Colombia until the last century (Defler 2004). Among the subspecies of C. calvus, C. calvus ucayalii is only found in northeastern Peru, confined to the south by the Sheshea River, to the north and west by the Amazon River and Ucayali River respectively, and in the east by the Yavari River (Aquino 1988; Heymann 1992; Ward & Chism 2003). C. c. rubicundus is restricted to the area around the mouth of the Japurá River (Barnett & Brandon-Jones 1997). C. c. novaesi is only found in a restricted area along the Juruá River, but probably has a wider distribution that needs further exploration (Barnett & Brandon-Jones 1997). C. c. calvus has a limited distribution between the lower Japurá and the Solimões and west to the Auatí-Paraná (Barnett & Brandon-Jones 1997; Silva Jr. & Martins 1999). However, it must be stressed that in many ways these distributions are preliminary, sometimes require confirmation, and likely will be expanded or changed with further research (see Barnett & Brandon-Jones 1997). An example of this is the discovery of a white uakari with pelage similar in appearance to C. c. calvus, some 700 km (434.0 mi) from its expected distribution (Silva Jr. & Martins 1999).

C. melanocephalus range (in yellow)
C. calvus range (in red)

Uakaris are extremely hard to maintain in captivity, a fact reflected by their low numbers in zoos and in the difficulty breeding captive individuals (Whitehead 1984; http://www.isis.org).

HABITAT

In general, uakaris are found close to or in flooded or riparian forests (Barnett & Brandon-Jones 1997). The habitats of the two species of uakari can be roughly separated by the types of rivers with which their habitat is associated. C. calvus, is found in habitats associated with "white-water rivers" while C. melanocephalus is found in habitats associated with "black-water rivers" (Ayres 1989; Barnett & Brandon-Jones 1997). This is not a rule however, as C. calvus has been seen around 60 km (37.3 mi) from any "white-water rivers" (Peres 1997). The habitat types and floodplains associated with the two different types of river have different features such as soil mineral content and richness and the primary floodplain habitats can generally be divided into two types várzea (associated with white-water rivers) and igapó (associated with black-water rivers) (Ayres 1989). Further, flooded forests of the Amazon exhibit profound changes in water level between the seasons. An example of this is at one study site, roughly 1200 miles (9131.2 km) west of Manaus, Brazil, where várzea water levels are 40 feet (12.2m) higher between March and August than they are during the rest of the year (Ayres 1990). However, uakaris can be found in several types of habitat, including flooded and unflooded igapó and várzea, swamp forest, various white sand soil forests, floodplains, terra firme forest near igapó and várzea, and transitional zones between flooded and terra firme forest (Ayres & Johns 1987; Ayres 1989; Boubli 1997b; Peres 1997; Aquino 1998; Defler 1999; Barnett et al. 2005a).

Some researchers suppose that uakaris are flooded-forest specialists while others comment that some or even most of their time is spent in terra firme forests and other habitat types (Ayres 1986 cited in Leonard & Bennett 1995; Leonard & Bennett 1995; Boubli 1997a; Aquino 1998). Either way, uakaris are not restricted to flooded or swamp forests (Bartecki & Heyman 1987). These other habitat types can be a good distance from water, sometimes 2 km (1.2 mi) from a river (Aquino 1998). In some cases, uakaris can be found in mountainous areas and sometimes range up to 1500m (Boubli 1994; 1997b). There appears to be some seasonal movement between habitats, with uakaris moving to flooded areas during periods of fruit abundance and preferring terra firme or other habitat types when more fruit is available outside of flooded forest (see Barnett & Brandon-Jones 1997; Barnett et al. 2005 for discussion and review). However, when restricted by geography, such a pattern is not seen (as is the case with C. c. calvus) and some researchers suggest that the seasonal situation is more complex than a simple bimodal model (Barnett & Brandon-Jones 1997; Barnett & de Castilho 2000).

At one study site, at the Pico da Neblina National Park in Brazil, rainfall averages 250-300 cm (98.4-118.1 in) per year and is almost evenly distributed throughout the months, however in a regional sense, the first half of the year is wetter than the second half. Temperature also varies little throughout the year, averaging around 26°C (78.8°F) (Boubli 1997a).

ECOLOGY

C. melanocephalus are predominantly frugivorous but specialize in the seeds of hard-husked unripe fruits. For C. melanocephalus, the recorded diet at one study site comprised of 89% fruits, 5% flowers, 4% leaves and leaf parts, and 2% invertebrates (including ants, spiders, grasshoppers, katydids and roaches). The concentration on unripe fruits is unlike any unlike other neotropical frugivores, and is helped by special dentition and a chewing apparatus which allows it to use foods which are unavailable to other primates (Ayres 1989; 1990; Boubli 1999). Up to 120 species of plant are exploited as food with a few preferred species making up a significant proportion of the diet. The seeds of fruits are extremely important in the diet, comprising the majority of fruit feeding observations (Boubli 1999). The majority of these come from unripe fruits. Fruits are often bitten along their sutures, which require less force to puncture (Adrian Barnett pers. comm.).

Cacajao melanocephalus
Photo: Luiz Claudio Marigo

The known diets of C. calvus are similar to those recorded for C. melanocephalus and C. ouakary, with seeds of fruits predominating (67% of observations) followed by other parts of fruit (10%), flowers (6%), nectar, some insects (5%) and unidentified foods (4%) (Ayres & Johns 1987; Ayres 1989). Aquino & Encarnación (1999) noted C. c. ucayalii eating 53 plant species from 20 families, of which 46% were consumed for their seeds. Of these, 67% had thick heavy husks and were consumed in the immature state. In the dry season, Peruvian red uakaris will also eat bromeliad leaf bases, and also move to unflooded forest to feed on palm fruit as well as (unspecified) flowers and leaves (Aquino & Encarnación 1994; Aquino 1995). For C. ouakary, larvae of wasps and the eggs of turtles are also reported as being eaten on occasion, with wasp nests raided by the species (Barnett 1999; Barnett et al. 2005a; Barnett 2008). Almost one hundred species of plant are eaten by C. calvus (Ayres 1989). Uakaris sometimes descend to the ground during specific times of the year and forage for seeds and seedlings (Ayres 1989; Barnett & de Castilho 2000; Barnett 2008). When fruits are in short supply, leaves and pith are consumed (Barnett 2005; 2008). In addition, during periods of relative fruit scarcity, uakaris will actually increase the amount of ripe fruit pulp they consume because during periods of fruit abundance, they will focus on unripe seeds and other abundant foods as preferred resources (Boubli 1999).

Uakaris are diurnal. The day of C. m. melanocephalus is spent resting (22%), traveling (27%), feeding (20%), and moving/foraging (31%). Over the course of the day, travel occurs most early and late in the day, resting peaks in the late morning or early afternoon, feeding is relatively constant, and moving/foraging is common in the morning and early afternoon (Boubli 1997a). The white uakari (C. c. calvus) begins its day at sunup and descends from the sleeping trees to feed. The troop will feed and move until noon with a period of rest around midday. In the mid-afternoon, the troop will resume feeding and moving and by dark, the group will have begun entering their sleeping site for the night (Ayres 1990).

Uakaris are characterized by very large day ranges, traveling up to 4.4 km (2.7 mi) or even 5 km (3.1 mi) per day during fruiting. Annual averages are often lower; in one study with small sample sizes they averaged 2.3 km (1.4 mi) per day (Ayres 1989; Boubli 1997a; 1999). They travel quickly (Boubli 1997b). Some subspecies range even farther, with one estimate placing the day range of C. c. ucayalii at an average of 7.3 km (4.5 mi) (Leonard & Bennett 1995; 1996). Ranging distances are dependent on the state of food availability and during the high-water fruiting season distances traveled are farther than during the dry season, when they are considerably shorter (Ayres 1990). Home ranges of C. m. melanocephalus (minimum estimate of 10.53 sq km (4.1 sq mi)) are larger than those observed for C. calvus (5.0-5.5 sq km (1.9-2.1 sq mi)), but some estimates for C. c. ucayalii place home range at a very large 30 sq km (11.6 sq mi) however, often the area within the home range that is used the majority of the time is smaller, as is the case with C. calvus (2.5-3.0 sq km (1.0-1.2 sq mi)) (Ayres 1989; Leonard & Bennett 1996; Boubli 1997).

Cacajao calvus calvus
Photo: Luiz Claudio Marigo

Harpy eagles (Harpya harpya) are a potential and actual predator of uakaris (Leonard & Bennett 1996; Boubli 1997a; Barnett et al. 2005b). Other potential predators include ocelots (Felis pardalis), tayras (Eira barbara) and Boa constrictor snakes. Uakaris often react to perceived aerial threats, including bird species that are not predators, such as toucans (Boubli 1997a).

In different locations, uakaris are sympatric with different primate species, but across their distribution, they can be sympatric with members of the genera Alouatta, Aotus, Callicebus, Chiropotes, Cebus, Lagothrix, Pithecia, and Saimiri (Leonard & Bennett 1996; Boubli 1999; 2002).

In some cases, uakaris are found in association with other primates including spider monkeys (Ateles sp.), wooly monkeys (Lagothrix sp.), sakis (Chiropotes sp. & Pithecia sp.), capuchins (Cebus sp.), and squirrel monkeys (Saimiri sp.) (Leonard & Bennett 1996; Aquino 1988; 1998; Boubli 2002). Such associations might provide predator protection and foraging benefits (Leonard & Bennett 1996).

Competition for food comes from species with dietary overlap with uakaris, such as macaws (Ara sp.), squirrels and sympatric primates such as squirrel monkeys and capuchins. Such overlap and levels of potential competition require quantitative assessment, but are probably low (Barnett 2005; Barnett et al. 2005a; Barnett 2008).

Sleeping occurs high in the trees, normally 17 (55.8 ft) to around 40 meters (131.2 ft) up, with the troop distributed in different trees over about an acre, with only 6-7 individual uakaris per sleeping tree (Ayres 1990; Aquino 1998).

Content last modified: July 21, 2008

Written by Kurt Gron. Reviewed by Adrian Barnett.

Cite this page as:
Gron KJ. 2008 July 21. Primate Factsheets: Uakari (Cacajao) Taxonomy, Morphology, & Ecology. <http://pin.primate.wisc.edu/factsheets/entry/uakari/taxon>. Accessed 2008 October 13.