Black-headed Uakari (Cacajao melanocephalus)

There is sexual dimorphism of size in this species. This species has a tail that is one-third the length of the head and body. This species has a dental formula of 2:1:3:3 on the upper and lower jaw (Hershkovitz, 1987). The incisors of this species are narrow and elongated (Hershkovitz, 1987). The molars of the black-headed uakari are simple and low-crowned (Kinzey, 1992; cited in Norconk et al., 1998). Males have larger canines and lower first premolars (Hershkovitz, 1987). The black-headed uakari has a body mass that ranges from 2.4 to 4 kilograms (Emmons, 1997).

This species has two subspecies each having their own distinctive pelage coloration:

The black-headed uakari is found in the countries of Brazil, Colombia, and Venezuela. This species lives mainly in the igapo forests (Barnett and Brandon-Jones, 1997; Defler, 1989). The subspecies Cacajao melanocephalus melanocephalus was found to live in yuacana and cunuri, caatingas, chavascal, and terra firma forest types (Boubli, 1997). This subspecies may rest in chavascal forests because it may offer them protection from predators due to that this forest type is swampy with a thick canopy cover (Boubli, 1999).

The subspecies have the following distribution:

The black-headed uakari is primarily a frugivorous species, but will also eat seeds, leaves, and insects; due to that seeds play an important part of this species diet it might be better to classify this species as a sclerocarpic frugivore. On the ground they forage for newly germinating seeds that largely remain uneaten because of a lack of large terrestrial mammals (Ayres, 1989). The subspecies Cacajao melanocephalus melanocephalus consumes the seeds of Cunaria sp. (Euphorbiaceae) and the subspecies Cacajao melanocephalus ouakary consumes the seeds of immature Eschweilera sp. (Barnett and Brandon-Jones, 1997). Cacajao melanocephalus melanocephalus has been found to feed on the seeds of the immature fruit of Manilkara sp. (Lehman and Robertson, 1994). The subspecies Cacajao melanocephalus melanocephalus has been found to consume the fruit of Manilkara sp. (Sapotaceae) and of Mauritia flexosa (Palmae) which have relatively thick shells (Barnett and Brandon-Jones, 1997). The subspecies Cacajao melanocephlus ouakary feeds on the fruit of Gomphiluma gomphifolium (Sapotaceae), Swartzia polyphylla (Papilionaceae), Aldinia latifolia (Caesalpiniacaeae), Manilkara surinamensis (Sapotaceae), and Hevea sp. (Euphorbiaceae) (Barnett and Brandon-Jones, 1997). In Colombia the most important fruit species consumed by this species is Eschweilera sp. (Defler, 1999). During the dry season this species consumes a large amount of noctuid caterpillars (Barnett and Brandon-Jones, 1997). This species migrates away from the igapo forests during the dry season due to the lower fruit production in these forests (Barnett and Brandon-Jones, 1997; Defler, 1989). When foraging this species pick immature fruit off of trees and carry it to a larger branch where the seeds are consumed (Lehman and Robertson, 1994).

In Pico da Neblina National Park, Brazil, the subspecies Cacajao melanocephalus melanocephalus was found to consume 89% fruit, 5% flowers, 4% leafy materials (leaves, petioles, bromeliads), and 2% arthropods (Boubli, 1999). Three species of plants were foraged on for there flowers, Pachira insignis, Eschweilera atropetiolata, and Eperua leucantha, with Eperua leucantha being consumed the most (Boubli, 1999). Petioles of Monstera adansoni and bromeliads comprised the majority of the leafy materials consumed (Boubli, 1999). This species was found to forage for the following arthropods: ants, spiders, grasshoppers, katydids, and roaches (Boubli, 1999). This species would catch flying arthropods, unroll dead leaves to find arthropods, peel bark off of dead branches, and scrape ant nests to find arthropods (Boubli, 1999). The most important fruit species consumed at this site is Micrandra spruceana (Boubli, 1999). This species is important because it will bear unripe fruit for a longer period of time compared to other species (8 months versus 3 months) (Boubli, 1999). During the early dry season fruit from lianas become important in the diet for this species living in Pico da Neblina National Park, mostly from the species Lysiostyles scandens and Dicranostyles ampla (Boubli, 1999). Seeds from unripe fruits accounted for 67% of the feeding records from this site (Boubli, 1999). The fruit species consumed by this subspecies are characterized by medium to hard husks, green, and have relatively large seeds (Boubli, 1999). During the early wet season this species consumes more seeds than fruit pulp due to that seeds are more abundant (Boubli, 1999). In this site the subspecies Cacajao melanocephalus melanocephalus may travel in large groups in order to exploit unpredictable resources that occur in large patches (Boubli, 1999).

This is an arboreal and diurnal species. The group size for this species ranges from 4 to 100 individuals (Barnett and Brandon-Jones, 1997). In Colombia it was found that the average group sizes for this species is 20-30 individuals (Defler, 1999). In Colombia groups tend to split up and come back together to form larger groups of around 100 individuals, and the smaller groups tend to be found when fruit is scarce and larger groups are found when there is an abundance of fruit (Defler, 1999).

The black-headed uakari moves through the forest in a variety of fashions including: quadrupedally, leaping, pronograde clambering, and dropping from a higher support to a lower one (Walker, 1993; cited in Kinzey, 1997). This species can suspend itself by its hindlimbs (Walker, 1993; cited in Kinzey, 1997). When this species moves more quickly, it will use a gallop or a bounding gait (Fontaine, 1981). In these types of quadrupedal locomotion the forelimbs move forward together followed by the hindlimbs moving together as one unit (Fontaine, 1981). Black-headed uakaris use leaps to cross gaps between trees in the canopy of the forest (Fontaine, 1981). This species is not a specialized leaper, so it needs to gain momentum before leaping by rocking back and forth on a branch (Fontaine, 1981). Adult males tend to be too large and can not leap as well as adult females and subadult males (Fontaine, 1981). When moving between terminal branches and twigs this species uses bridging where the forelimbs are flung on to the new support then moving each hindlimb on to the new support (Fontaine, 1981). Brachiation does occur in this species but mostly in the context of juvenile play (Fontaine, 1981). Black-headed uakaris can move bipedally but the surface must be relatively flat, and this behavior most often occurs on the ground (Fontaine, 1981). Bipedal locomotion most often occurs during juvenile play (Fontaine, 1981). When traveling this species tend to move just above the water in vines and bushes (Boubli, 1994; cited in Rowe, 1996).

The black-headed uakari has a polygynous mating system (Kinzey, 1997). This species has a fission-fusion social organization (Defler, 1999). Fission-fusion is described as being "any primate species that is observed in groups which vary greatly in number in the same area being studied" (Defler, 1999). Defler (1999) suggests that a fission-fusion type of social organization might be a tactic to allow a more efficient and economic foraging mode. However in Brazil, fission-fusion was not observed for this species, the black-headed uakari was found to live in multimale-multifemale groups (Boubli, 1997). This species forms mixed-species associations with Saimiri sciureus, Cebus apella, and Cebus albifrons (Fontaine, 1981). Adult females often will travel with juveniles and engage in social grooming with them for extended periods (Boubli, 1999).

chirp: This call serves to maintain contact between group members when moving and/or foraging (Boubli, 1997).

hic: This call is staccato in nature and is emitted in a series (2 to 20) (Fontaine, 1981). This call has an average duration of 35 milliseconds and a fundamental frequency that ranges from 425 hertz to 1.65 kilohertz (Fontaine, 1981). This vocalization is described as occurring in situations of "widely variable exteroceptive and proprioceptive stimuli" (Fontaine, 1981). This behavior is performed by all individual except adult males (Fontaine, 1981).

genital sniffing: This is when one black-headed uakari bends down and sniffs the genitalia of another. This behavioral pattern is used in greeting.

piloerection: This is when an individual will piloerect the pelage of the dorsum and external limb surfaces (Fontaine, 1981). This display is seen during attacks of both conspecifics and different species, loud noises, and as a defensive threat posture (Fontaine, 1981). This behavior is performed by both sexes from older juveniles on up (Fontaine, 1981). This display serves to communicate moderate to intense fear and aggression (Fontaine, 1981). This behavior makes the individual look larger (Fontaine, 1981).

tail wagging:This is when an individual will wag the tail from side-to-side (Fontaine, 1981). This display is seen after squabbles and at the end of grooming (Fontaine, 1981). This display is performed by both sexes of older infants on up (Fontaine, 1981). This communicates general arousal on the part of the sender (Fontaine, 1981).

social grooming: When one individual grooms another, usually removing dead skin and parasites. This is used to reinforce social bonds within the group.

The black-headed uakari gives birth to a single offspring.

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Last Updated: October 5, 2003.
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