The wedge-capped capuchin or Guianan weeper capuchin (Cebus olivaceus) is a capuchin monkey from South America. It is found in northern Brazil, Guyana and Venezuela. Cebus olivaceus is known to dwell in tall, primary forest and travel over long distances during the day. These primates are medium-sized monkeys with distinctive "wedge cap" markings on their head and slightly longer limbs than other capuchins for jumping through the forest canopy. Similar to other capuchin monkeys, the diet of wedge-capped capuchin primarily consists of fruits, invertebrates, other plant parts, and on rare occasions small vertebrates. They have also been known to rub millipedes against their fur, especially in the rainy seasons, as a potential means of mosquito repellent. Cebus olivaceus is a polygamous species that lives in groups of anywhere from 5-30 individuals with female-biased sex ratios. The group is organized according to a pre-determined hierarchal system of dominance for both males and females. Although biological lineage is less of a factor of dominance for males than it is for females, due to male migration between groups. Wedge-capped capuchin partake in several behavioral mechanisms to assert and maintain dominance within the group including: infanticide, when an infant is deliberately killed; grooming, used to facilitate social rapport; and alloparenting, which is when members of the group care for offspring that are not their own. The wedge-capped capuchin is listed as Least Concern in the IUCN Red List.
Taxonomy The genus Cebus is divided into several different species. However, taxonomists argue over the specific divisions within the genus, which are uncertain and controversial. The chestnut capuchin (C. castaneus) of northeastern Brazil, southern Guyana, French Guiana, and Suriname, as well as the brown weeper capuchin (C. brunneus) of northern Venezuela, were both previously considered subspecies of the wedge-capped capuchin, together being referred to as the weeper capuchin. However, a 2012 study found grounds to separate them as distinct species from one another, although this taxonomy is still highly contentious. The American Society of Mammalogists, IUCN Red List, and ITIS all follow this taxonomy, although only tentatively.
Description
Size and physical description Adult wedge-capped capuchins weigh approximately 3 kg (6.6 lb), but weight varies moderately with sex. They receive their name from a black triangle of dark fur centered on their foreheads. Generally this species is light brown to brown with yellow and gray tinges on varying parts of their bodies. Their "wedge cap" starts between the eyes and extends backwards to cover the top of the head. Their faces are hairless and surrounded by light brown or blonde fur.
Wedge-capped capuchins show similar levels of sexual dimorphism as other capuchin monkeys. On average, males weigh about 30% more than females. Additionally, males have relatively longer canines than females (even after overall body size is accounted for). Male maxillary and mandibular (upper and lower) canines of males are on average 70% and 40% larger than female canines respectively. This may be indicative of male competition for females.
Locomotion and morphology Wedge-capped capuchins have been compared to tufted capuchins to discern the relationship between locomotion and skeletal proportions. Wedge-capped capuchins spent relatively more time running and jumping through the forest canopy while tufted capuchins spent more time walking and moving slowly. As such, wedge-capped capuchins have relatively longer limbs (particularly the hind limbs) than tufted capuchins.
Phylogeny Due to large physical variations in Cebus, taxonomists have frequently debated the exact classifications and details of the genus. However, most agree that the wedge-capped capuchin shares the genus with four others: C. apella, C. albifrons, C. capucinus, and C. kaapori. The wedge-capped capuchin has a diploid chromosome number of 52, though some others in the genus have 54 chromosomes. Nine human chromosomes correspond to those of the C. olivaceus. Phylogenetic analysis and constructions of cladograms have demonstrated that the wedge-capped capuchin is closely related to C. apella.
Habitat and range
Wedge-capped capuchins prefer undisturbed primary forests in which they can move through the canopy (locomotion and limb morphology). They occupy the rainforests of northern Brazil and Venezuela, as well as the drier forests along riverbeds in Guyana. These habitats vary in terms of forest height, composition, and continuity. When wedge-capped capuchins have the option between dense high-canopy primary forests and more fragmented, lower forests, they generally inhabit the primary forests. They are found north of the Orinoco River, south of the Sierra de Perijá and Venezuelan Coastal Range, and east to the Essequibo River in western Guyana.
Diet Wedge-capped capuchins are omnivorous and eat both animal and plant foods. Foraging behavior varies seasonally, as well as with age and sex. In general, these monkeys spend approximately equal amounts of time exploiting animal and plant resources. The exception to this are infants that spend far more time foraging for plants foods than animals. Most of the plant food consumed is ripe fruit, the majority of which are figs, but also palm nuts, seeds, berries, flowering buds, shoots, barks and gums. Their animal prey is almost exclusively invertebrates. Their prey consists of snails, arachnids, wasps, caterpillars, grasshoppers, ants, birds eggs, other small mammals and many insects that inhabit palm crowns. Some coastal populations may also include oysters, crabs, and other marine life in their diet. While males and females spend about the same amount of time foraging for insects, they exploit different types of resources. Males spend more time searching for insects on the surface of branches, while females search for most of their insects atop palm trees. There is little variation in plant material consumed between males and females. Also, adults and sub-adults eat more animal material than juveniles and infants.
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