Howler Monkey

Brown Howler Monkey

The loud calls made by these monkeys indicate their presence and deter neighbouring troops from invading their feeding territory, thereby avoiding conflict.

Brown howler monkeys have a very unusual way of digesting their food. As with all animals that feed on vegetation, they need beneficial microbes to break down the cellulose present in the cell walls of the plants they eat. These are concentrated in two areas of the stomach, and produce volatile fatty acids as a by-product of the breakdown process. It is these gases that are absorbed in the body and help to meet the monkey’s energy needs.

Distribution: Occurs in southern parts of South America, in southeastern Brazil and northeastern Argentina. May also be found in adjacent areas of Uruguay and Bolivia.

Weight: 4 -7 kg (8.8 - 15.4 lb); females are smaller.

Length: 93 - 126 cm (37 - 50 in) overall; the tail is slightly longer than the body.

Maturity: Females 3 years; males 3.5 years.

Gestation Period: About 190 days.

Breeding: 1; weaning occurs at 12 - 13 months; females give birth every 1.5 - 2 years.

Diet: Feeds on vegetation and fruit, depending on the time of year; also eats invertebrates.

Lifespan: Up to 20 years.


This is free of fur, allowing facial gestures, indicating the monkey’s mood, to lie seen clearly.


Unlike other species, the brown howler monkey does not regularly stage a dawn chorus.

Sounding off

There are often several males in a troop. Disputes are rare but fights between males and females do occur.


The fur is longer around the face, creating the appearance of a beard.


The hands have five digits, with the first finger and thumb opposing the other three.


Howler monkeys are relatively inactive, resting during the day when they are not feeding, although they are more active in winter, when food is scarcer.

Mantled Howler Monkey

One of the few primate species to live as far north as Mexico, this species also lives along the eastern side of Central America and in northern Colombia and Ecuador. Mantled howler monkeys live in both lowland rainforests and upland montane forests. They eat mainly leaves and fruit, preferring young leaves that have lower levels of indigestible tannins in them. In the dry season, they supplement their diet with flowers. Fruits are more common in the wet season. The monkeys move slowly through the forest; their energies are devoted to consuming large amounts of food.

Mantled howler monkeys have yellow or brown saddle-shaped patches on their back, and long hairs along their flanks. Both sexes possess a beard, with the males having longer facial hair. The males also have a conspicuous white scrotum.

Mantled howler monkeys live in groups of 10-20 individuals. There are generally three or four females for every male in the group. These males tend to be at least 6 years old. Younger males live alone or in small groups that contain no females. As in other howler monkey species, the males make loud, persistent calls, which can be heard for up to 3km (1.86 miles). Females initiate mating by wiggling their tongue at a male. He responds in the same way and mating follows soon afterwards.

Distribution: Southern Mexico, Central America, northern Colombia and Ecuador.

Habitat: Forests.

Food: Leaves, fruits and flowers.

Size: 38 - 58 cm (15 - 23 in); 3 - 9 kg (6.5 - 19.75 lb).

Maturity: 3 years.

Breeding: 1 young produced every 2 years.

Life span: 12 - 25 years.

Status: Common.

Red Howler Monkey

Howlers are large monkeys that live in the trees of tropical forests. They are known for the roaring howls that fill South American forests. The monkeys have very wide jaws, which allow them to open their mouths wide and make such loud calls.

Howler monkeys roar first thing in the morning before setting off to look for food. Although they eat fruits, such as figs, when they are available, howler monkeys rely for long periods on just leaves. Few other monkeys have such an unvaried, indigestible diet. After a rest in the middle of the day, the monkeys feed some more before travelling back to their sleeping trees while howling to each other again.

Howler monkeys typically have reddish-brown hair, although some have a more yellowish or dusky coloration. Their strong prehensile tails have naked patches on their undersides to help them grip branches. The males are larger than the females and generally have darker hair. The loud calls of these monkeys, especially by the males, are made possible by a specialized larynx in the throat, which amplifies the sound.

Howler monkey troops contain about eight or nine individuals. Larger troops form when there are more fruits available. Males compete with each other to join troops, and the victors may kill the young of the males they depose. The howling call is thought to be a mechanism for locating nearby troops. These monkeys breed all year round. The young ride on their mothers’ backs for up to a year. Both males and females leave their mothers’ troops when they are sexually mature and join others.

Distribution: Northern South America.

Habitat: Rainforest and mangroves.

Food: Leaves and figs.

Size: 55 - 92 cm (21.5 - 36 in); 4 - 10 kg (8.75 - 22 lb).

Maturity: 4 - 5 years.

Breeding: Single young born throughout the year.

Life span: 20 years.

Status: Endangered.

Black Howler Monkey

Size: 51 - 67 cm (20 - 26.5 in); 4 - 10 kg (8.75 - 22 lb).

This monkey lives in the forests of central South America, from northern Argentina to southern Brazil and eastern Bolivia. It inhabits either flooded gallery forests beside rivers or dry deciduous forests that grow in patches close to savannahs. Like other howlers, this species is a folivore - a leaf eater. Black howler monkeys live in family groups with a few more females than males. Male offspring are chased away as they mature.