GUIANAN WEEPER CAPUCHIN

Cebus olivaceus

Geographic Distribution and Habitat
Guianan weeper capuchins (Cebus olivaceus), also known as wedge-capped capuchins or weeper capuchins, are native to South America, with populations ranging from the Venezuelan Amazon Basin to the drier forests along the Essequibo River in Guyana. They also occupy the forested area between the Branco River and the Araca River in Brazil. They prefer high-canopy primary forests but will travel to the understory and forest floor for foraging purposes. The habitat range is classified as subtropical to tropical moist lowland, which is characterized by high levels of rainfall, humid climate, and low variability in annual temperature.

Weeper capuchin geographic range, IUCN 2020

Size, Weight, and Lifespan
Guianan weeper capuchins are comparable in size and weight to other species of capuchin, with adult males weighing approximately 6.6 pounds (3kg) and measuring about 20 inches (55 cm) in length. They possess a prehensile tail, which is typically the same length of the body and provides the monkey with leverage and support while foraging amongst wobbly tree branches. As with other capuchin species, gender dimorphism is present, with males weighing roughly 30% more than females. Male Guianan weeper capuchins also have significantly longer canines than females. The average lifespan of a Guianan weeper capuchin in the wild is between 30 and 40 years, with those in captivity living up to 50 years.

Appearance
As we have learned, Guianan weeper capuchins are also referred to as wedge-capped capuchins due to the distinctive, triangular patch of dark fur atop their heads. This unique marking creates the appearance of a dramatic widow’s peak, similar to that of Eddie Munster, a character on the popular 1960s family sitcom “The Munsters.”

Their coats are thick and vary in shades of brown with tinges of blonde and gray throughout the fur. Their hairless, pinkish faces are framed by lighter fur, ranging from light brown to blonde. The lighter fur generally dominates the torso, and often the arms and inner leg, while hands and feet range from dark brown to black.

Wedge-capped capuchins have deep-set, quizzical brown eyes and, as is typical of New World monkeys, broad and flat muzzles with side-facing nostrils. Compared to some other capuchin species, Guianan weeper capuchins have longer arms and legs, which enable them to deftly run and jump throughout the forest canopy. Their long prehensile tail is typically slightly coiled at the tip. The tail is used more for balancing and leaning than for gripping and dangling from branches.

What Does It Mean?

Allomothering:
Females in a troop share responsibility for caring for the young. Individuals other than the biological mother of an offspring perform the functions of a mother (by caring for an infant temporarily).

Gender dimorphism:
When the two sexes of the same species have differences in body structure, or anything beyond their sexual organs.

Gestation period:
The time of pregnancy from conception until birth. 

Matrilineal society: 
Is based on a line of descent through the female. Offspring are traced back to the mother as opposed to a patrilineal society, from which descent is traced to the male.

Visit the Glossary for more definitions

Butch Patrick as Eddie Munster (CBS Television Network., Public domain, via Wikimedia Commons)

Diet
Guianan weeper capuchins enjoy a varied omnivorous diet consisting of nuts, seeds, fruit (particularly berries and figs), and small animals such as snails, insects, and bird eggs. Males tend to forage for insects within tree branches, while females prefer to focus on foraging in tree tops. Observed patterns of food intake suggest that plant and animal resources are exploited equally, though predation risk can significantly influence these patterns.

Infants and juveniles primarily consume plant materials, suggesting that predation habits are learned from adults within the group. Guianan weeper capuchins have been observed participating in food-washing in the wild and in captivity, though scientists believe this behavior is most likely circumstantial rather than an example of protoculture.

Behavior and Lifestyle
As is typical of most New World monkeys, Guianan weeper capuchins are diurnal, meaning that the majority of their activity takes place during the daytime. They are considered arboreal, spending most of their time in the forest canopy, occasionally venturing to the ground in search of food and water.

Foraging for food occupies much of the day, with troops traveling long distances through the forest canopy and sleeping in groups at night among tree branches. Their primary mode of locomotion is quadrupedalism (moving on four limbs), though they are capable of standing and walking upright. Bipedalism (standing on two legs) is sometimes used when utilizing stone tools to crack open hard nuts. In this instance, the tail is crucial to providing balance while the monkey strikes the stone against the nut. This behavior is more common in capuchin species such as bearded capuchins, who are more inclined to travel on the ground than weeper capuchins are. 

A Guianan weeper capuchin behavior that is not completely understood is the practice of rubbing millipedes against the fur, called “self-anointing,” and sometimes even sharing the millipedes among the group. They have also been observed placing millipedes in their mouths before continuing to rub them against their fur. Scientists theorize that the millipedes may release certain chemicals when under stress, which may act as an insect repellent against mosquitoes. This theory is further strengthened by the fact that the behavior is more common during the rainy season when mosquito numbers are highest.

Fun Facts

Capuchins are named for their “caps” of hair, which resemble a capuche, the cowl worn by a Capuchin friar. 

Daily Life and Group Dynamics 
Almost all monkeys travel in troops, and Guianan weeper capuchins are no exception. Troops consist of anywhere from 5 to 30 individuals, with juveniles and females making up the majority of the group. This population structure is due to young males emigrating from their natal group between the ages of 3 and 6 in search of new troops. Ideally, a male immigrates into a group with a high ratio of females to adult males, which increases his chances of mating. Females rarely leave their natal groups, and the status of females within the troop is typically established by matrilines, meaning that social hierarchy is based on kinship among the females. This lineage is less common for males due to their habit of leaving the natal group.

Grooming behavior is an important practice for establishing group dynamics. Juvenile males and females will seek opportunities to groom adults with the purpose of integrating themselves into the adult social structure of the troop. This is particularly important for young females, as they will lose access to resources if they fail to establish relationships with older females. As a result, young females rarely groom each other. Interestingly, adult females tend to groom lower-ranking females, though how the grooming is initiated depends on two observed grooming strategies. Firstly, a subordinate adult female may try to initiate grooming when approached by a higher-ranking female in the hope of avoiding confrontation. Often, when a high-ranking female approaches a subordinate, aggressive behavior ensues. Laying down and submitting to grooming can diffuse the situation. The second grooming strategy is affiliative, meaning that its purpose is to form social bonds and alliances. This type of grooming typically takes place among females with less disparity in rank and can offer social and material advantages to both participants.

Communication
Unsurprisingly, Cebus olivaceus is referred to as the Guianan weeper capuchin because it makes sorrowful sounds similar to weeping. However, these primates use many unique sounds and facial expressions to communicate. For instance, high-pitched screams are used to alert the troop of predators, such as jaguars, boas, caimans, and birds of prey. They may bare their teeth and scream at intruders of the same species as a sign of aggression and dominance. Lip-smacking and swaying is associated with positive interactions such as grooming or intercourse. 

Reproduction and Family
These monkeys are polygamous, meaning that males within the group will mate with multiple females. Birth rate coincides with age, with younger females giving birth more frequently. A female between the ages of 6 and 26 may give birth up to once every 2 years, while a female older than 26 may give birth every 3 to 4 years.

Females reach sexual maturity at about 4 to 6 months, which is slightly earlier than males who reach sexual maturity between the ages of 7 to 9 months. Breeding typically takes place during the time of year when resources are most plentiful, which is between October and February. The average gestation period is about 160 days, and usually only one infant is birthed per pregnancy.

Infants are nursed an average of 2 to 4 months before they are weaned. During this time, the infant will be cared for almost exclusively by the mother. Males are not involved with infant care, but females within the troop alloparent—which is when an infant is cared for by someone other than the parents. Siblings are more likely to alloparent than troop members who are not related. Additionally, juveniles and young adult females are more prone to allomaternal behavior than older females, a trait that is common in other primate groups and suggests that younger females gain valuable experience by helping raise infants. A behavior that is common to Guianan weeper capuchins but rather rare in other primate groups is allonursing, which is when a mother nurses an infant that is not her own. Interestingly, this practice is not connected to relatedness, but rather to reciprocity, meaning that performing the favor of nursing another’s infant is eventually reciprocated. 

Incidents of infanticide (the deliberate killing of infants) have been observed. Males immigtating to new troops will sometimes engage in infanticide because a female without an infant may be more likely to mate, ensuring his genes infiltrate the troop.

Photo credit: Heribert Dezeo/Creative Commons

Ecological Role
Guianan weeper capuchins disperse seeds through their feces, which helps replenish their own food source and that of other organisms relying upon the same resource. They also help control insect populations, and as a prey species they can affect predator populations. Guianan weeper capuchins play a vital role in the food web of their ecosystem, and an increase or decrease in their population would have a direct impact on other organisms.

Conservation Status and Threats
Guianan weeper capuchins are classified by the International Union for Conservation of Nature (IUCN, 2015) as Least Concern, appearing on the IUCN Red List of Threatened species. Projected forest loss for their geographic range is expected to be 10% or less for the current and subsequent two generations (2019–2066). Current evidence also shows minimal hunting of the species, which also contributes to the current conservation status assessment.

Capuchin monkeys are popular exotic pets and suffer terribly as they are typically purchased by individuals who have no knowledge of the complex physical, psychological, and social needs of primates. Capchins are not pets and, when forced to live as such, they endure a life of constant lack and frustration, which can lead to them inflicting serious injuries upon their owners. As an individual, you can make the choice to not promote the exotic pet trade by refraining from sharing cute videos of pet primates on social media. Educate those around you to do the same! 

Conservation Efforts
Guianan weeper capuchins are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES). CITES is an international agreement between governments to ensure that the international trade of wild animals and plants does not threaten the survival of the species.

Nonprofit organizations such as the Wild Capuchin Foundation work to support scientific research of capuchins, the education and training of scientists in primate behavior, habitat conservation, and education for the general public.

References:

  • Fleagle, J. G. (2013). Primate Adaptation and Evolution. ScienceDirect. Retrieved February 16, 2022, from https://www.sciencedirect.com/book/9780123786326/primate-adaptation-and-evolution 
  • Fragaszy, D. M., Visalberghi, E., & Fedigan, L. M. (2004). The Complete Capuchin: The biology of the genus cebus. Cambridge University Press. 
  • Urbani, Bernardo. “Spontaneous Use of Tools by Wedge-Capped Capuchin Monkeys (Cebus olivaceus).” Folia Primatologica 70 (1999): 172 – 174. 
  • https://animaldiversity.org/accounts/Cebus_olivaceus
  • https://capuchinfoundation.org 
  • https://fieldprojects.org/a-trick-of-the-tail-prehensile-tails-and-primate-evolution/
  • https://www.iucnredlist.org/species/81384371/191708662n 
  • https://www.speciesplus.net
  • https://www.worldanimalfoundation.org/advocate/wild-animals/params/post/1288402/capuchins 

Written by K. Scarlett Hebert, February 2022