Black and Gold Howler Monkey

The Black and Gold Howler Monkey is a large New World monkey notable for its striking sexual dichromatism, with males being entirely black and females golden-yellow to olive-brown. It inhabits forested regions of south-central South America and is renowned for its extremely loud howling vocalizations that can carry for several kilometers through dense forest. This species plays a key ecological role as a seed disperser in gallery and semi-deciduous forests. It is one of the most cold-tolerant howler species, surviving in subtropical forests with seasonal temperature drops.

Northern Argentina, Paraguay, Bolivia, and southern/central Brazil

Found in northern Argentina, Paraguay, southeastern Bolivia, and Brazil (Mato Grosso, Mato Grosso do Sul, and parts of the Pantanal and Cerrado biomes), primarily in the Gran Chaco and Pantanal regions.

Altitude and depth

0–500 m above sea level

Seasonal movements

No true migration, but activity levels and diet shift seasonally with dry and wet seasons; leaf consumption increases during fruit-scarce dry periods.

Gallery forests, semi-deciduous and deciduous forests, flooded forests, and forest fragments along rivers; also found in secondary growth and forest edges adapted to seasonal flooding and dry periods.

Adaptations to its environment

Possesses an enlarged hyoid bone that amplifies vocalizations for long-distance communication, reducing energetic costs of territorial defense. A slow metabolism and folivorous diet allow it to survive on lower-quality food resources, and a prehensile tail aids in arboreal locomotion and feeding stability.

Near Threatened (NT) according to IUCN, with populations declining due to habitat loss and fragmentation across its range, though it remains relatively widespread and adaptable compared to other howler species.

Estimated population

Population size is not precisely quantified but is considered declining, with significant local extinctions following yellow fever epizootics in Argentina and Brazil in the 2000s-2010s.

Deforestation for agriculture and cattle ranching, habitat fragmentation, yellow fever outbreaks causing mass mortality, hunting, and illegal pet trade.

Diseases and parasites

Highly susceptible to yellow fever, which has caused significant population crashes; also affected by various intestinal parasites and botflies (Cuterebra) common in Neotropical primates.

Protected under national wildlife laws in Argentina, Brazil, Paraguay, and Bolivia; present in several protected areas including El Rey National Park (Argentina) and various Pantanal reserves; some rehabilitation and reintroduction programs exist following disease outbreaks.

Recommended actions

Strengthen habitat corridors between forest fragments, implement yellow fever vaccination buffers for wildlife, enforce anti-deforestation laws, and monitor population health through long-term field studies.

Males are entirely black with a shaggy coat, while females and juveniles are golden-yellow to pale brown; both sexes have a long prehensile tail with a bare, sensitive underside for gripping branches.

Size

Body length (head-body) 40–65 cm, with a prehensile tail of similar or greater length (55–70 cm).

Weight

Males typically weigh 5–7 kg; females are smaller, weighing 3.5–5 kg.

Distinctive features

Extreme sexual dichromatism (black males vs. golden females) is unique among howler monkeys and distinguishes this species from congeners like the red howler (Alouatta seniculus) or mantled howler (Alouatta palliata), which show little to no color difference between sexes.

Differences between males and females

Pronounced dichromatism: males are black, females are golden-yellow; males are also notably larger and possess a more developed hyoid bone for deeper howls.

Lives in cohesive social groups of 5–19 individuals, typically with multiple adult males and females; groups display a loose dominance hierarchy with minimal aggressive interactions compared to other primates.

When it is active

Diurnal, with peak activity in early morning and late afternoon; spends much of the day resting to conserve energy due to its leaf-heavy diet.

Diet

Primarily folivorous-frugivorous, feeding on young leaves, fruits, flowers, and occasionally bark; diet shifts seasonally based on resource availability, with leaves dominating during dry periods.

Communication

Famous for loud, resonant howls produced by an enlarged hyoid bone, used for territorial spacing and group coordination, especially at dawn and dusk; also uses facial expressions, body postures, and scent marking for social communication.

Interactions with other species

Predators include large birds of prey (harpy eagles), felids (jaguars, ocelots), and occasionally snakes; competes with other primates and frugivorous mammals for fruit resources but generally occupies a distinct dietary niche due to folivory.

Role in its ecosystem

Acts as an important seed disperser for various tree species in gallery and semi-deciduous forests, contributing to forest regeneration and plant diversity maintenance.

Breeding occurs year-round without a strict seasonal pattern; gestation lasts approximately 185–190 days, typically resulting in a single offspring; weaning occurs around 12–18 months.

Raising the young

Mothers provide primary care, carrying infants ventrally then dorsally as they grow; other group females may occasionally assist in alloparental care, and males show tolerance toward infants within the group.

Maturity and lifespan

Sexual maturity is reached around 3–5 years; lifespan in the wild is approximately 15–20 years, with captive individuals sometimes living over 20 years.

Classification

Mammalia > Primates > Atelidae > Alouatta > Alouatta caraya

Scientific synonyms

Mycetes caraya (Humboldt, 1812); Stentor caraya

Recent studies

Recent research has focused on the demographic and genetic impacts of yellow fever epidemics on wild populations, revealing severe local population bottlenecks and slow recovery rates in affected regions of Argentina and Brazil.

Genome and DNA

Diploid chromosome number of 2n=52; genetic studies have been used to assess population structure and impacts of yellow fever outbreaks on genetic diversity.

Compared with similar species

Unlike the mantled howler (Alouatta palliata) or red howler (Alouatta seniculus), which show minimal sexual color dimorphism, Alouatta caraya exhibits striking black-vs-gold sexual dichromatism, making it visually distinct among howler species.

Their howls are among the loudest calls of any land animal, audible up to 5 km away; males are born golden like females and only darken to black as they mature; they are one of the few New World primates capable of surviving subtropical winters with occasional frost.

Where and how to see it

Best observed at dawn or dusk in gallery forests of the Pantanal or northern Argentine provinces like Formosa and Chaco, where their loud howls make them easier to locate; guided ecotourism tours in Iberá Wetlands (Argentina) offer good sighting opportunities.

Risks to humans

No notable risk to humans; they are generally shy and avoid direct contact, though captive or habituated individuals may bite if provoked.

Human uses

Occasionally kept illegally as pets due to their striking appearance; historically hunted for bushmeat in some rural areas, though this practice has declined with conservation awareness.

Myths and legends

In some local folklore of the Gran Chaco and Pantanal regions, the howler monkey's calls are associated with impending rain or storms, and its haunting roar has inspired legends of forest spirits in indigenous Guaraní traditions.