Black-and-Gold Howler, Alouatta caraya
BLACK-AND-GOLD HOWLER
Alouatta caraya
Geographic Distribution and Habitat
Black-and-gold howler monkeys, also known as black howler monkeys, are native to central South America. More specifically, their range includes eastern Bolivia, southern and central-western Brazil, eastern Paraguay, northern and northeastern Argentina, and northwestern Uruguay (though their occurrence in Uruguay has minimal research). Some of the most common regions they can be found in include the Pantanal, Cerrado, Caatinga, Chaco, Pampa, and Atlantic Forest.
Being rather adaptable creatures, these howlers are able to live in a wide range of forest types and elevations; they inhabit both moist and dry forests, including montane (high elevation forests perched alongside mountain slopes), gallery (tree forests growing alongside a natural, permanent water source), woodland, and seasonally flooded forests, but tend to favor areas near rivers or floodplains. As a testament to their adaptability, black-and-gold howler monkeys have also often been observed living in forest fragments that have been compromised by human-led developments.
Size, Weight, and Lifespan
Black-and-gold howler monkeys are hailed as some of the largest monkeys in South America. They are sexually dimorphic, meaning there are noticeable differences in size and/or appearance between males and females. In general, males have a head-body length of around 24-26 inches (60–65 cm), while their smaller female counterparts average at around 20 inches (50cm). On top of being longer, males also weigh quite a bit more than females, ranging from 13-17 pounds (6-7.7 kg) compared to the 10-pound (4.5 kg) average weight for females.
These monkeys’ prehensile tails (able to grasp branches) can add up to 30 inches (76 cm) to their total length. The furless underside of their tail enhances their natural grip, contributing to their impressive climbing prowess.
In the wild, black-and-gold howlers generally live between 15 and 20 years, but those raised in captivity often surpass 20 years of age.
Appearance
You might be a bit confused as you scroll through the pictures on this webpage and notice two different-colored monkeys, but there’s a reason for that! This species is not only sexually dimorphic, but are also sexually dichromatic, meaning males and females are differently colored. Males have a black coat, while females are responsible for the “gold” in the species’ name, with their lighter, blonde coloring. It’s worth noting that both males and females are born with this lighter coloration, which helps them blend into their mother’s fur as they cling to her back before becoming independent.
These monkeys are often seen in a hunched position while resting, giving them a plump appearance. Their long tails extend behind them, with the last third of the underside hairless to help grip branches; this prehensile tail acts like a fifth limb, aiding in climbing and moving through the trees.
They have dark, rounded eyes and a slightly protruding, rounded snout. Their mouths typically rest in a downturned position, though they are often seen forming an “O” shape when communicating with one another or other neighboring animals.
Diet
These monkeys are primarily folivores, meaning they specialize in a leaf-rich diet, but they also consume various fruits (mainly wild figs), buds, flowers, vines, seeds, bark, and mosses. A majority of their food intake is sourced from high in the forest canopy, allowing them to stay in the trees as they prefer; black-and-gold howler monkeys rarely travel to the ground floor, primarily only doing so to drink from bodies of water. Unlike many of the other primate species found throughout the Americas and who prefer younger leaves that are easier to digest and more nutrient-dense, these howlers tend to stick to mature leaves. This species has developed a unique digestive system to combat this tougher diet: on top of the acid in their stomachs, they have two large parts in the intestines called the caecum and colon that store a type of bacteria which can further break down the tough cellulose in the leaves they eat, fermenting it to produce energy. They also have strong molars specifically adapted to chew through the fibrous leaf material.
Seasonal changes in food supply, namely the reduction in fruit around the winter seasons, motivate changes in the black-and-gold howler monkey diet and can even affect their gut microbiome, highlighting their impressive ecological flexibility.
Behavior and Lifestyle
Black-and-gold howler monkeys are highly social, diurnal (active during the daytime), and primarily arboreal (live in trees). They spend most of their time in the upper and middle layers of the forest canopy and sleep where it’s safest among the highest branches. They travel quadrupedally (using all four limbs) through the tree branches. In addition to helping them climb, they use their prehensile tails to assist with foraging and eating by wrapping them around branches, allowing them to hang downward.
Due to the low caloric value of their leaf-dense diet, conserving energy is very necessary for this species. According to various studies, these monkeys can spend anywhere between 57 and 67% of their waking time resting. When they travel, they tend to move very slowly so as to not expend unnecessary effort.
Since there are many other species, including other primates, living within the same ecosystems as black-and-gold howler monkeys, it is necessary that they establish their territories to avoid confrontation. To do this, dominant males will produce a series of deep, resonant howls that echo through the forest each morning to protect their home ranges. Sometimes other members of the group, including females, will participate in these calls.
Black-and-gold howler monkeys have a highly advanced sense of smell and are able to detect food from distances of up to 1.2 miles away (2 kilometers).
Black-and-gold howler monkeys live in very social groups that can range from 5 to 19 individuals, with varying gender/age composition. Smaller groups are typically led by one dominant male, alongside several adult females and their offspring; larger troops may have 1-3 adult males. The dominant male within a group, usually the biggest in size, is in charge of maintaining troop order and leading activities. Other adolescent males often leave their natal groups, sometimes forming bachelor (all male) troops, while females tend to remain in the group they were born into.
Play and grooming behaviors help to solidify bonds, with grooming sessions lasting around 15 minutes and play-based behavior occurring across all age levels.
Black-and-gold howler monkeys are some of the loudest animals within their ecosystem, getting their name from their echoing, guttural howls that can be heard up to 3 miles (4.8 kilometers) away. These calls are primarily performed by males, who have an enlarged hyoid bone that makes this possible. The hyoid bone is a “U”-shaped bone in the middle of the neck between the chin and thyroid cartilage. These howls not only establish and protect their territorial boundaries, but can also be used to maintain group cohesion.
Howler monkeys also rely on plenty of other non-vocal forms of communication. For example, specific tongue-flicking expressions are used to express sexual interest during mating interactions. They will also rub themselves onto branches to mark their territory with their scent, or sometimes even participate in group defecating behaviors that create easily detectable piles of feces (also used to mark their territory).
Lastly, like most other primates, tactile communication is key in building healthy relationships within their groups, including play and grooming.
Black-and-gold howler monkeys are polygynous, meaning both males and females have multiple sexual partners. Breeding occurs year-round, with mating often being initiated by females. They have a range of tricks to initiate this contact, including grooming, tongue-flicking, and sometimes just following around a male with whom they are smitten. Once impregnated, gestation lasts between 180 and 194 days, with females typically giving birth to a single infant (twins are possible, but rare).
Newborns have lighter colored fur and cling to their mother’s bellies for a month before transitioning to riding on her back. While the mother is usually the primary caregiver, other females in the group sometimes help care for the infant, a behavior known as allomothering. The young are considered independent by 12 months of age, though they don’t reach sexual maturity until around 3 to 4 years of age for females and about 5 years for males. At this stage, both males and females emigrate from their natal groups to form new troops.
Folivores like howler monkeys are essential to controlling the canopy size and sunlight reaching the forest floor. Trees are the climax species in rainforests, meaning they are the ecosystem’s largest and most complex structures. They maintain that status by spreading out as much as possible to get the most sunlight for photosynthesis, the process by which plants make food. This means that canopies block out the sun for many smaller plant species, which prevents these shorter, less established plants from taking root or growing. Folivores eat a lot of leaves and create light gaps in the canopy that allow sunlight to reach the forest floor. The shorter plants can photosynthesize in these gaps.
The black-and-gold howler monkey’s survival is closely tied to the quality of the rainforest. Their adaptation to high canopies and a more leaf-eating diet allows them to share the forest resources, in terms of space and food, without competition. This resource-sharing increases the complexity of an ecosystem and makes the rainforest better suited to adapting to changes in weather, climate, and human disturbances.
In addition, due to the fruit in their diet, black-and-gold howler monkeys play a role in forest seed dispersal. As they eat, seeds may fall from their mouths, while others pass through their digestive systems and are deposited in their feces, often with the added benefit of natural fertilization. Additionally, some seeds hitch a ride by sticking to their fur as the monkeys travel from branch to branch! Lastly, although unfortunate for the howlers, they sometimes serve as prey for larger predators such as harpy eagles and felids.
The black-and-gold howler monkey is classified as Near Threatened by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. Their primary threats include habitat destruction, hunting, and disease outbreaks such as yellow fever.
Humans have been slashing their natural habitats at alarming rates in order to obtain wood and fuel, and to create room for agricultural expansions like soy farms and cattle ranches. Though this species is resilient and the monkeys can adapt to some changes in their environment, the ongoing loss of natural habitat continues to pose a serious threat, especially in regions like the Argentine provinces of Formosa, Misiones, Salta, and Corrientes. If current trends continue, it is predicted that nearly 40% of the leftover habitable zones of the Brazilian Amazon will be lost by 2050.
These awe-inspiring animals are also hunted for their meat and fur, and have even been captured for laboratory use in the United States.
Black-and-gold howler monkeys are 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.
There is a large list of protected areas and national parks that these monkeys can reside in, including around 40,000 square miles (10,300,000 hectares) in Bolivia, 32,400 square miles (8,400,000 hectares) in Brazil, 4200 square miles (1,000,000 hectares) in Paraguay, and 498 square miles (129,000 hectares) in Argentina.
There are also multiple organizations that have made strides to protect these beautiful creatures. Para La Tierra, a Paraguayan nonprofit, aims to protect black-and-gold howler monkeys living in the city of Pilar. One of their most notable initiatives is their “Adopt a Monkey” program, which raises funds for education campaigns, scientific studies, and conservation projects.
The Rufford Foundation provides support to conservation projects in South America that study the ecology of howler monkeys and the threats they face, striving to guide conservation strategies and raise awareness through community-based education programs.
In 2024, the Primate Society of Great Britain, in partnership with the Born Free Foundation, awarded a £1,500 conservation grant to scientist Nicolas Gorostiaga. He will use the funds to support his ongoing work in Argentina studying the yellow fever outbreak that has killed hundreds of howler monkeys.
Much work still needs to be done to protect these incredible animals.
- https://www.iucnredlist.org/species/41545/190414715#geographic-range
- https://animalia.bio/black-howler-monkey?taxonomy=366
- https://link.springer.com/chapter/10.1007/978-1-4939-1957-4_3
- https://link.springer.com/chapter/10.1007/978-1-4939-1957-4_3
- https://onlinelibrary.wiley.com/doi/10.1002/ajp.21010
- https://onlinelibrary.wiley.com/doi/10.1002/ajp.20389
- https://link.springer.com/article/10.1007/s10329-022-00975-5
- https://onlinelibrary.wiley.com/doi/10.1002/(SICI)1096-8644(199808)106:4%3C533::AID-AJPA8%3E3.0.CO;2-J
- https://onlinelibrary.wiley.com/doi/10.1002/ajp.23241
- https://elischolar.library.yale.edu/library_map_prize/2/
- https://link.springer.com/article/10.1007/s10329-003-0072-6
- https://pubmed.ncbi.nlm.nih.gov/25524570/
- https://elischolar.library.yale.edu/library_map_prize/2/
- https://link.springer.com/article/10.1007/s10329-003-0072-6
- https://pubmed.ncbi.nlm.nih.gov/25524570/
- https://pubmed.ncbi.nlm.nih.gov/19034383/
- https://link.springer.com/article/10.1007/s10764-010-9430-6
- https://www.beardsleyzoo.org/black-and-gold-howler-monkeys.html
- https://onlinelibrary.wiley.com/doi/10.1002/ajp.20838
- https://www.researchgate.net/publication/269404296_Interactions_of_Howler_Monkeys_with_Other_Vertebrates_A_Review
- https://www.rufford.org/projects/antonio-rob%C3%A9rio-gomes-freire-filho/endangered-howler-monkey-conservation-project-northeast-brazil-population-dynamics-anthropic-threats-and-private-protected-areas/
- https://www.bornfree.org.uk/news/psgb-winner-2024-a-win-for-black-and-gold-howler-monkeys/
- https://www.paralatierra.org/adopt-a-monkey
Written by Hannah Broadland, May 2025