Cacajao hosomi

Geographic Distribution and Habitat

Neblina uakaris (pronounced “wakari”), also known as black-faced uakaris or black-headed uakaris, live in the rainforests of Brazil and Venezuela. Their distribution is limited by the Amazon River’s large tributaries that cut through both countries. In Brazil, Neblina uakaris are boxed in by the Rio Negro in the south and west and the Rio Marauiá in the east. In Venezuela, they are not found north of Canal Cassiquiare and Rio Orinoco.

Within their geographic range, Neblina uakaris can live in the diverse forest types within the Amazon rainforest. These forest types range from white sand forests called “caatinga,” swamp forests called “chascaval,” and never-flooded forests called “terre firme.”

Their common name, Neblina uakari, comes from the mountain region Pico da Neblina, where these uakaris were first described. Most of the studies on wild Neblina uakaris have been conducted in the Pico da Neblina National Park in Brazil. This area is one of the most isolated parts of the Amazon forest and the Yanomama indigenous tribe members are the only native human inhabitants.

One of the challenges in studying Neblina uakaris is accessing their habitat in the Amazon forest because there are only a few roads and no buildings or modern infrastructure. This makes setting up research stations with equipment and living facilities difficult. Another challenge is that Neblina uakaris live in the canopy of dense tropical forests, where it is difficult to observe them for long periods of time. 


Black uakaris are an under-studied group of primates that were once classified as only two species found on the left and right banks of the Rio Negro. The Neblina uakari was elevated to a distinct species in 2008. They get their species name hosomi from the indigenous Yanomami tribe’s word for uakari monkey.

Some researchers do not agree with the species status of the Neblina uakari and instead think that these uakaris should be classified as a subspecies of the golden-backed uakari (Cacajao melanocephalus), which is also, rather confusingly, referred to as the black-headed uakari. Experts agree that Neblina uakaris are found only on the left bank of the Rio Negro and currently most publications consider Neblina uakaris as a separate species.

Published works on Neblina uakaris are lacking because they are a newly recognized species. Neblina uakaris were described from observations in Pico da Neblina National Park. This is considered the center of their range, where it is unlikely that Neblina uakaris would overlap with other black uakari species’ ranges. Prior to 2008, studies on black uakaris in Pico da Neblina were most likely on Neblina uakaris but they were unknowingly classified as a subspecies of golden-backed uakaris.  

Neblina uakari range, IUCN 2022

Size, Weight, and Lifespan

Neblina uakaris are medium-sized primates; however, they are larger than most other uakari species. Males weigh about 10 pounds (4.5 kg). Females are smaller, weighing around 7 pounds (3.1 kg). Their head-to-body length is between 17 and 19 inches (43.5–48.5 cm) and their tail is shorter, between 14.3 and 7.5 inches (36.54–45 cm).

The Cologne Zoo in Germany held a Neblina uakari in their primate collection for about 18 years. That is the longest that this species has been documented to live in captivity. The lifespan of wild Neblina uakaris is not documented. In general, other wild uakari species live to about 20 years of age.


Neblina uakaris have a long, thick, reddish brown pelage from the mid-back all the way down to their tails. Their chests and bellies are similarly colored, but the hair is shorter. Other black uakaris species tend to have more black or golden coloring on their backs. Neblina uakaris have blackish long hairs on their heads which look like bangs that cover their ears. Their black faces are hairless. Their tails are much shorter than their bodies, which is an unusual trait for tree-dwelling primates who typically need long tails for balance as they jump between branches. 

There is no sexual dimorphism in Neblina uakaris, which means that males and females look similar. 

Photo credit: @jean boubi/iNaturalist/Creative Commons

Neblina uakaris eat a lot of seeds. Even when they feed on fruits, they crack open the seeds inside them to eat them. This is unlike most other primates, who tend to throw away the hard-to-eat seeds. So, Neblina uakaris are able to take advantage of food sources that most other animals in the rainforest ignore, thereby avoiding resource competition. Neblina uakaris depend on more than 120 tree species for food and tend to specialize in eating hard unripe fruits with seeds.

The Amazon forest may seem green and lush year-round, but there are months in which trees do not produce fruits. In these low-food times, usually between August and October, Neblina uakaris eat insects. They also feed on leaves, flowers, and nectar when seeds are scarce.

Water is not a limitation in their environment. In fact, their habitat is flooded for many months. The monkeys use their hands to scoop and drink water that is collected in leaves.

To bite and chew such hard seeds, Neblina uakaris have large teeth and powerful jaw muscles. These adaptations allow them to reach the inner fat-rich part of the seed. Fat has more calories than carbohydrates (which are found in fruits), but it takes more time and effort to crack open and eat seeds. Neblina uakaris have no need to wait until the fruit ripens to eat the seeds. There are, therefore, more food sources available to them throughout the year than for primates that depend on fruit alone. So, the energy it costs Neblina uakaris to break through the seed is made up for by the benefit of getting a high-energy meal. This trade-off between energy cost and nutrition benefit is like taking the effort to make a balanced, homemade meal that will give you lots of energy for the entire day. For other primates, that focus on eating only fruits and throwing away the seeds is like eating a more convenient fast-food meal that will give you a sudden burst of energy, but you will have to eat again soon.

Behavior and Lifestyle

Neblina uakaris are active during daylight hours (diurnal) and tree-dwelling (arboreal). They walk using all four limbs (quadrupedal movement) and also leap between branches, sometimes as far as 32 feet (10 m). They are capable of walking on their two hind legs (bipedal motion), but this has only been noted in captive individuals. It is not a common way for wild Neblina uakaris to move.  

When they jump, Neblina uakaris usually have to do so from higher branches to lower ones. They land on their legs before they use their arms to stabilize themselves. Their short tails do not offer much assistance in balancing.  

Neblina uakaris constantly wag their short tails. This behavior is seen in other closely related primates and probably helps them relieve tension, similar to how people fidget or bounce their legs when they sit. They are probably not even aware that they are doing it.

Color vision may play an important role in how Neblina uakaris sense their world. Recent studies revealed that they have genetic adaptations that produce light-sensitive proteins called “opsin” that can help develop color vision. Color vision can help with differentiating types of fruit from a distance and may even help the monkeys recognize color variations in an individual’s fur or appearance.

Daily Life and Group Dynamics

Neblina uakaris spend 31% of their day foraging, 20% actually eating, 27% traveling, and 22% resting. They live in large troops ranging from 30 to 100 individuals. Members of the troop rarely travel together in a cohesive unit. There is usually a lot of space between individuals. The exceptions to loose-knit grouping are mothers and their young, who usually forage and travel together. 

The large troop size and the tendency of the troop to spread out can be explained by the availability of seeds throughout the forest. A single tree can produce multiple seeds, but the trees that have seeds grow in patches or clumps. This means that there is low competition for food between the uakaris, but they have to spread out in order to reach the food patches. Often only four Neblina uakaris are seen feeding at a tree. There is no need to overcrowd.

In the mornings, the troop will wake up and slowly travel in spread-out groups to forage. Once they find food, they spend a lot of time with a piece of fruit as they tear away at the outer layers to reach the goodness inside. Sometimes they sit and focus on feeding, but it seems that they are constantly eating throughout the day, even as they travel to and from food patches. Neblina uakaris have large home ranges they travel through during their lifetimes. They travel an average of 0.7–2.2 miles (1,103–3,497 m) per day as they forage for food.

Neblina uakaris sometimes spend time allogrooming, where individuals groom each other, but it does not seem to be too common. In general, there seems to be little conflict between individuals, even males.

When the day gets hot, many members of the troop will rest, usually lying down on branches, dangling their legs. Mothers and their babies rest together. Juveniles play while their parents take a break. Other members may continue to move on and look for food. This dynamic within the troop tells us that Neblina uakaris are social, but mostly independent primates that do not need to stay in tight groups. This may be a result of low predation risk. Primates usually stay together in troops as a defense system, to detect and fight off predators. Neblina uakaris have potential predators that live in their habitat, but the risk is probably low enough that they can stay in loosely knit groups.


The specifics about how Neblina uakaris communicate are relatively unknown, but we can rely on closely related uakari species to help us with some aspects of uakari biology that is used to communicate. For example, sternal glands (found on the chest) are documented in both sexes of other uakari species. These glands are most likely used to scent-mark trees or attract the opposite sex. This behavior has been noted for some other primate species.

Constant “keeks” or “chics” calls are made as a way for them to keep in contact with other group members when they are spread out.

Reproduction and Family

We do not have a lot of information about Neblina uakaris but we can assume that their biology is similar to the closely related white uakari (Cacajap calvus calvus). Pregnant Neblina uakaris are likely to endure a gestation period of six months and give birth during the rainy season when trees produce the maximum amount of fruit. 

Like other uakaris, we think Neblina uakaris have multi-male, multi-female groups. Mothers carry infants, while one to three juveniles walk close to her. Male Neblina uakaris are more patient with juveniles than some other primate species. Adult males tolerate juveniles jumping on their backs or playfully clambering on them.

Ecological Role

The Neblina uakari’s role in the food web of the Amazon forest contributes to the working of the ecosystem as a whole. They are a potential food source for harpy eagles and ocelots that can hunt in the canopy. 

Many aspects of Neblina uakari ecology, such as their larger home range and group size, are explained by their diet of high-nutrient seeds. Eating high-calorie seeds provides enough energy for them to travel long distances.

Neblina uakaris may help pollinate flowers as they feed on nectar and move between flowering plants, but they do not play a role in seed dispersal because they eat all the growing parts of the seed. In the Amazon forest, tree density and seed production are large. Not all seeds can become trees because there would be too much competition for resources like light and soil. If too many trees or plants compete for the same resources the quality of tree health in the forest will be negatively affected. Neblina uakaris help forest health by consuming seeds that cannot become trees because of overcrowding.

Neblina uakaris share their habitat with other seed predators that are also potential competitors such as macaws, toucans, and bearded sakis (Chiropotes chiropotes). The coexistence of all these species in the same habitat means that the Neblina uakari’s adaptation to other food sources (insects, leaves, and flowers) gives them the ability to share the resources without always competing for them.

Conservation Status and Threats

The International Union for Conservation of Nature lists the Neblina uakari as Vulnerable (IUCN, 2016), appearing on the IUCN Red List of Threatened Species. Hunting is the main threat against their decreasing population. This information is gathered mostly from hunting data. 

The Yanomami people regularly hunt primates for food. Neblina uakaris often forage near rivers, which makes them easy targets for hunters. In the last century, Christian missionaries built larger villages for the Yanomami people and introduced them to more modern ways of life. The introduction of medicine and better healthcare increased their life span and population size. Traditional hunting technologies, such as bows, are now replaced by more advanced rifles that have increased the hunting success rate and resulted in rapid local declines of Neblina uakari populations. 

Garimpeiros, also called wildcat miners, are small-scale gold miners who work in remote areas of the Amazon rainforest searching for gold ores along the rivers. However, garimpeiros’ gold mining activities are often illegal and include deforestation and extensive mercury contamination of rivers. Researchers are particularly concerned with the habitat contamination and poisoning of Neblina uakaris and other wildlife.

Conservation Efforts

The Neblina uakari is listed in Appendix I 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. This is the highest level of protection. Species in Appendix I are threatened with extinction and prohibited from any trade, though there may be some rare exceptions, such as old museum specimens may be purchased. 

Locally, the Neblina uakari’s habitat is protected through the Brazilian Environment Institution (IBAMA).

The Neblina uakari was only described in 2008 and this new status means that there is still a lot we have to learn about the species, especially their population numbers. Conservation policies need to be updated to include the Neblina uakari and their survival needs. Making policy and governmental changes take years to adapt and more time to implement, which makes the conservation of vulnerable species like the Neblina uakari difficult.

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Written by Acima Cherian, December 2022