Humboldt’s White-Fronted Capuchin, Cebus albifrons
HUMBOLDT’S WHITE-FRONTED CAPUCHIN
Cebus albifrons
Geographic Distribution and Habitat
The Humboldt’s white-fronted capuchin monkey is endemic to Brazil, Colombia, and Venezuela, specifically in the northern Amazon regions. They can be found in different forest types ranging from dry-deciduous forests to flooded rainforests and mangrove forests. They are also known as brown pale-fronted or pale-fronted capuchin monkeys.
White-fronted capuchin monkeys can be difficult to tell apart from other capuchin species in the wild. Historically, Cebus albifrons was classified with multiple subspecies, which makes the taxonomy of white-fronted capuchin monkeys complex. Genetic studies of wild populations have revealed more variation between species than previously thought. Therefore, some subspecies are now classified as separate species. Some researchers think that the Humboldt’s white-fronted capuchin monkey distribution is limited to the north of the Solimoes River in Brazil.
Size, Weight, and Lifespan
Humboldt’s white-fronted capuchin monkeys are long-limbed, slender monkeys with a head-and-body length of about 15 inches (37 cm) and a long tail of 17 inches (42 cm). Male Humboldt’s white-fronted capuchin monkeys weigh 4–7 pounds (1.7–3.3 kg), and females weigh 3–5 pounds (1.4–2.3 kg). At birth, baby white-fronted capuchin monkeys weigh about 7–8 ounces (225–247 g).
One captive Humboldt’s white-fronted capuchin monkey lived to be 40 years old! Reports from other capuchin monkey species indicate that individuals in the wild may live to be 25 years old.
Appearance
Humboldt’s white-fronted capuchin monkeys are gracile capuchins, characterized by a slender, delicate build. Their backs are light gray-brown with darker limbs and yellowish-brown hands and feet. The front or underside of the body is is cream colored. Their body hair looks a lot like the texture and color of the trees they spend most of their time around. The skin of their faces is pink and their forehead hair is pale compared to the rest of their head. A dark brown wedge-shaped cap stands out from their lighter forehead.
Adult male capuchin monkeys are generally larger than adult females, and visually you can tell them apart (making them sexually dimorphic). Males appear to have larger jaws, skulls, and canine teeth than females. The males also have visible testicles, which makes distinguishing between males and females easier for field researchers.
Diet
These versatile monkeys are omnivorous with a diet of fruits, seeds, invertebrates (like insects and spiders), and even some vertebrates (like rodents). Some of their favorite foods are cucuritu palms and platanota. But they also steal crops from nearby farms, particularly corn or maize.
Humboldt’s white-fronted capuchin monkeys are active foragers and will raid nests of freshwater turtles for eggs. Eggs are highly nutritious foods and these monkeys go through the trouble of looking for concealed nests and digging through dirt and plants to get to the eggs.
They drink water every day and do not just rely on the moisture from their foods for hydration, as some other primate species do. They get water from the dew that collects on leaves as well as from streams, and sometimes they drink water that gets collected in tree holes. They often remember the location of these small, temporary water sources. Capuchin monkeys will intentionally change direction to visit these watering holes for a drink before continuing on their journey.
Behavior and Lifestyle
Humboldt’s white-fronted capuchin monkeys are diurnal (active during the day) and tend to be arboreal (live in trees), but, as you will find out, these monkeys are capable of thriving in many different environments.
The capuchin monkey’s ability to observe their environment and take action to satisfy their goal of getting a protein-packed meal is one indication of how intelligent these primates are. Scientists use a measure called EQ (Encephalization Quotient) to indicate how big an animal’s brain is compared to their body. A larger EQ means that an animal has a larger brain which it uses to navigate the world, find food, and survive. Humans have an EQ between 7.4–7.8 and capuchin monkeys have an EQ of about 4.5, which is larger than a chimpanzee’s EQ! The larger brains in capuchin monkeys can explain their complex social and ecological behaviors and their ability to adapt to different environments.
These capuchin monkeys have flexible behaviors and modify their feeding strategies depending on where their food is present at that moment. In the dry season, when fruits are rare, Humboldt’s white-fronted capuchin monkeys look for palm leaves that curl into tubes as the leaves dry out. These leaf tubes are the perfect housing for insects that seek shelter from the heat. The monkeys will spend about half an hour at a palm tree, painstakingly looking for these leaf tubes and stripping them of any insects or spiders that are hiding there. They look for maggots in rotting carcasses and break open rock-like termite nests to get grubs. This shows that even if food sources are hidden in a smelly carcass or an underground nest, these monkeys find a way to eat these foods—even if it takes a lot of energy.
If a favorite food is around or the food is packed into a small space, troop members are comfortable feeding right next to each other and have a high tolerance for members entering their personal space. As a troop, this tight-knit group helps to protect all members from predators or rival troops. However, if the food is spread out in the forest, a troop of capuchin monkeys moves in wide bands. Sometimes monkeys might be 8 feet (250 m) apart. With this strategy, the risk of being caught by a predator is higher because the monkeys cannot effectively scan a large area for threats.
These capuchin monkeys are not afraid to leave the safety of the trees and will cross grasslands and bare rocks to reach a good food patch. And while they are on the ground they will opportunistically feed on flowers or fallen fruits. Humboldt’s white-fronted capuchin monkeys are successfully able to adapt to different environments, which makes them better skilled at surviving changes in their habitat due to deforestation and climate change.
Grooming behaviors are seen mostly between mothers and infants. Grooming not only gets rid of dirt and pests stuck in their fur, but it also strengthens social bonds just as humans feel good when they cuddle or hug a loved one. Grooming sessions among adult Humboldt’s white-fronted capuchin monkeys are short (less than a minute) and not a big part of their social aspect compared to other primate species.
We only have studies of wild Humboldt’s white-fronted capuchin monkeys from a few areas and so we have to make generalizations for the entire species, but it is important to be aware that the same species can behave differently in different regions due to local environmental factors. Assuming all Humboldt’s white-fronted capuchin monkeys behave the same across their entire range would be like saying all humans have the same lifestyles as people living in Los Angeles! However, capuchin monkey experts think that Humboldt’s white-fronted capuchin monkey behavior is similar to other closely related gracile capuchin monkeys. Other white-fronted capuchin monkeys have been observed using leaves as cups to get water from tree cavities! Such tool uses are often seen in capuchin monkeys in the wild and in captive settings. Some white-fronted capuchin species also rub themselves with mud, which is a common capuchin monkey behavior called self-anointing. Self-anointing is when monkeys cover themselves with some foreign substance (like mud, oils from herbs or citrus leaves, and even ants). Researchers think that these monkeys use the insect-repelling qualities of oils or natural chemicals to protect themselves. This kind of behavior is seen in other primates and is once again a window into how capuchin monkeys can identify and use the resources around them.
Humboldt’s white-fronted capuchin monkeys eat almost anything they can get their hands on, including insects, frogs, rodents, fruits, and flowers.
They are highly intelligent animals that can use tools to get their food.
White-fronted capuchins perform self-anointing—where they rub mud or plants all over themselves—as protection from insect bites or as soothing remedies to insect bites.
The day starts early for Humboldt’s white-fronted capuchin monkeys. They wake up at around 5:30 am, when the sun rises. After their morning bathroom routines, they set off to find breakfast. They travel long distances in search of food and sometimes have a home range as large as 296 acres (120 ha). Around midday, when it is too hot for strenuous activity, they rest in the trees for about 1–3 hours, depending on the weather. During this time they lazily forage, sleep, and groom each other, and young monkeys will play in the shade around their family. After their afternoon siesta, they continue to forage for more food and head back to their sleeping trees around 4:00 pm, well before the sun sets. Traveling at night is dangerous because it is hard to see the way home. Also, predators hunt at night. They spend the twilight hours playing, grooming, and winding down to sleep.
These capuchin monkeys sleep in trees, usually about 65–100 feet (20–30 m) above the ground. They have favorite sleeping trees, especially if they are close to their favorite foods during the fruiting season. They will also switch sleeping sites to have better access to these fruits.
Males organize themselves in a hierarchy, or pecking order, with usually the largest and most dominant or alpha male taking the primary role of protecting the troop from rivals or predators. The alpha male’s fur is often puffed up (a phenomenon called piloerection), and you can also identify him by his vigilant stance and alert nature when the troop members are traveling to food sites. Once an adult female was seen jumping on the back of the alpha male when she mistook a researcher as a threat. The alpha male carried her off to safety in that jockey style!
The alpha is not only the protector of the troop, but he also maintains peace and order in the troop. Most loud outbursts from troop members will make the alpha interrupt them and stop any further fighting.
There is not much known about the different ways these intelligent primates communicate with each other. It is possible that at close range they use facial expressions and hormones to indicate when they are nervous or ready to mate, much like other capuchin monkey species. Baring their teeth in a grimace is also a common reaction to rivals or threats. However, we do know that vocal communication plays a big part in their life.
An alpha male will stare unblinkingly at a potential predator or threat, slowly bare his teeth, and puff up his fur to show how big he is as if to say, “Best be on your way and not mess with me!” He also makes showy displays such as swinging across the canopy where he usually jumps on or throws a dead tree limb. This results in the branch crashing noisily onto the forest floor. He does not vocalize during these displays, though onlooking troop members will bark with excitement. The whole display draws the attention of the predator away from young capuchin monkeys in the troop and shows everyone how strong the alpha is.
Vocalizations are used mostly to communicate excitement and aggression. Males make a loud “yah!” call when they fight with opposing troops. When different troops encounter each other, it usually ends in aggression with males yelling and chasing each other. Males and females make a “wah” barking noise and an “eh-eh” call when confronting threats such as researchers or predators. An “arrh” sound was used to contact troop members when they are spread apart. Troop members would repeatedly use the “arrh” sound to draw in members especially if a sudden rainstorm appears. “Uch! Uch!” sounds made while traveling through the canopy means that they are telling the straggling troop members to keep up! Young Humboldt’s white-fronted capuchin monkey will make high-pitched chattering noises called “twitter” sounds when they want to get close to the alpha male. He allows them to hang out with him and even touch him, but usually, the alpha is busy doing his duties and the young cannot catch up to him.
An average troop contains between 19 and 20 monkeys with multiple males and almost the same number of females. However, populations vary in different regions. In one Colombian population of Humboldt’s white-fronted capuchin monkeys, a troop had 35 individuals consisting of twice as many females as males. Males and females have their own hierarchical structure or dominance order, but males have higher status than females.
Mating occurs between multiple males and females, and the alpha male may get the most mating opportunities. Females are pregnant for about 5 months and give birth to one baby at a time. Capuchin monkey infants cling to their mother’s back like a jockey riding a horse. The young take at least a year to a year and a half to become independent of their mother. Initially, the mother is the main caretaker but, after a few weeks, other females help nurse and take care of the baby. Once young capuchin monkeys can eat solid food, all troop members help feed and care for the young.
Males are highly protective of the troop and gentle with infants and juveniles. Males carry young monkeys through the canopy and even rush to pull the young to safety at the sign of a threat. Adults also join in on playtime with the young capuchin monkeys.
When juvenile males become sexually mature, at around 3.5 years old, they leave their natal troop, while females remain with their natal family.
We know that Humboldt’s white-fronted capuchin monkeys travel long distances and feed on fruits and flowers. It is highly likely that they drop seeds along the way or help pollinate flowers as they move through the canopy. They also feed on multiple parts of the food system, from insects to frogs. This flexibility also means that the presence of Humboldt’s white-fronted capuchin monkeys affects different parts of the forest food chain and ecosystem.
Capuchin monkeys are an important food source for raptors such as the black-and-white hawk-eagle and harpy eagle.
Humboldt’s white-fronted capuchin monkeys live in peace with other primate species even though there may be competition for food resources. They seem to be more aggressive towards members of their own species, which most likely indicates a higher level of competition within the same species (intra-specific competition). It is possible that the varied diet of Humboldt’s white-fronted capuchin monkey reduces the competition for other primate species (Inter-specific competition) and so there is no need for territorial behaviors most of the time.
The International Union for Conservation of Nature lists Humboldt’s white-fronted capuchin as Least Concern (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. Their distribution spans multiple countries and habitat loss is not as severe for the Humboldt’s white-fronted capuchin monkey as it is for other species. While habitat loss in the Amazon is a concern for all animals in the region, Humboldt’s white-fronted capuchin monkeys are adaptable enough to find food and survive in their changing ecosystem. Even with farming and monoculture (growing one kind of crop which eventually harms the soil and ecology of the farm), these capuchin monkeys are able to find food by raiding crops.
Population numbers vary in different parts of their distribution. Some reserves have as many as 115 individuals per square mile (46 individuals per sq. km.) while others only have 20 individuals per square mile (8 individuals per sq. km). Currently, their numbers are decreasing.
Hunting and the pet trade are threats to population growth, particularly with mature individuals. When reproductively mature individuals are taken out of the population, it decreases the potential for new offspring. Additionally, with a large amount of parental care in capuchin monkeys, fewer adults can also affect the chances of young individuals surviving into adulthood.
Humboldt’s white-fronted capuchin is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
The IUCN’s Least Concern status puts these capuchin monkeys lower on the conservation priority list. Therefore there are no specific actions to protect the Humboldt’s white-fronted capuchin monkey. However, efforts to protect forests in that region will have positive effects on the population. The Humboldt’s white-fronted capuchin monkey’s geographical range spans multiple protected areas where hunting and deforestation are prohibited.
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Written by Acima Cherian, April 2023