Any of several species of slow-moving tropical American monkeys (genus Alouatta) noted for their roaring cries, which carry over a distance of 2–3 mi (3–5 km). Five widely distributed species are the largest New World monkeys, generally reaching lengths of 16–28 in. (40–70 cm), excluding the 20–30-in. (50–75-cm) tail. Howlers are stoutly built and bearded, with a hunched appearance and a thickly furred, prehensile tail. Their hair is long and thick and, depending on the species, black, brown, or red. Howlers live in groups in territories mapped out by howling matches with neighbouring clans. They feed primarily on leaves.

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Howler monkeys (genus Alouatta monotypic in subfamily Alouattinae) are among the largest of the New World monkeys. Nine species are currently recognised. Previously classified in the family Cebidae, they are now placed in the family Atelidae. These monkeys are native to South and Central American forests. They live in groups of usually about 18 individuals. Threats to howler monkeys include being hunted for food and captivity.

Etymology

Their name comes from their distinctive loud barking whoop they make, which can be heard over considerable distances. William Henry Hudson pointed out in his novel Green Mansions, "howler" is a misnomer since the male's voice sounds rather like a powerful roar; female vocalisations sound like a pig's grunt.

Howlers are called "congos" in Nicaragua and Costa Rica. In Belize they are called "baboons", although they are not closely related to the genus Papio, which usually carries that name.

Classification

• Family Atelidae
• Subfamily Alouattinae
• A. palliata group
• Coiba Island Howler, Alouatta coibensis
• Alouatta coibensis coibensis
• Azuero Howler Monkey, Alouatta coibensis trabeata
• Mantled Howler, Alouatta palliata
• Ecuadorian Mantled Howling Monkey, Alouatta palliata aequatorialis
• Golden-mantled Howling Monkey, Alouatta palliata palliata
• Mexican Howling Monkey, Alouatta palliata mexicana
• Guatemalan Black Howler, Alouatta pigra
• A. seniculus group
• Red-handed Howler, Alouatta belzebul
• Brown Howler, Alouatta guariba
• Northern Brown Howler, Alouatta guariba guariba
• Southern Brown Howler, Alouatta guariba clamitans
• Guyanan Red Howler, Alouatta macconnelli
• Amazon Black Howler, Alouatta nigerrima
• Bolivian Red Howler, Alouatta sara
• Venezuelan Red Howler, Alouatta seniculus
• Colombian Red Howler, Alouatta seniculus seniculus
• Alouatta seniculus arctoidea
• Juruá Red Howler, Alouatta seniculus juara
• A. caraya group
• Black Howler, Alouatta caraya
• Subfamily Atelinae

Anatomy and physiology

Howler monkeys have a short snout, and wide-set, round nostrils. They range in size from 56 to 92 cm, excluding their tail which can be equally as long. Like many New World monkeys, they have prehensile tails. Unlike other New World monkeys, both male and female howler monkeys have trichromatic colour vision. This has evolved independently from other New World monkeys due to gene duplication. They have a lifespan of 15 to 20 years.

Locomotion

They move quadrapedally and do not brachiate, usually holding on to a branch with at least two hands or one hand and the tail at all times. Their prehensile tails are strong enough to support the monkey's entire body weight, although they seldom do so. The first 2 fingers of each hand are set apart and are opposable to the other three. They very seldom leave the trees. They rest about 80 percent of the time and are considered the least active of all monkeys.

Behaviour

Social systems

Howler monkeys live in groups where the number of females is greater than the number of males. Groups may have only one male or several males. Unlike most New World monkeys, juveniles of both genders emigrate from their natal groups, so neither adult males nor adults females in a group are typically related. Fighting among group members is infrequent and generally of short duration. However, serious injuries can result. Both males and females may fight with each other. Group size varies by species and by location, with an approximate male to female ratio of a male to four females.

Communication

As their name suggests, vocal communication forms an important part of their social behavior. They have an enlarged basihyal or hyoid bone which helps them make their loud sound. They are considered the loudest land animal. According to Guinness Book of World Record it can be heard clearly for 3 miles.

Diet and feeding

These large, slow moving monkeys are the only folivores of the New World monkeys. Howlers eat mainly top canopy leaves, together with fruit, buds, flowers, and nuts. They need to be careful not to eat too much of certain species of mature leaf in one sitting, as some of the leaves they eat contain toxins that can poison the monkey.

Relationship with humans

While seldom aggressive, howler monkeys do not take well to captivity and are of surly disposition, and hence are the only monkey in their forests not made a pet by the Native Americans . However, the Black Howler (Alouatta caraya) is a relatively common pet monkey in contemporary Argentina due to its gentle nature, in comparison to the capuchin monkey's aggressive tendencies, in spite of its lesser intelligence as well as the liabilities meant by the size of its droppings and the males' loud vocalisation.

Alexander von Humboldt said about howler monkeys that "their eyes, voice, and gait are indicative of melancholy", while John Lloyd Stephens described those at the Maya ruins of Copán as "grave and solemn as if officiating as the guardians of consecrated ground". To the Mayas of the Classic Period, they were the divine patrons of the artisans, especially scribes and sculptors. Copán in particular is famous for its representations of Howler Monkey Gods. Two howler monkey brothers play a role in the 16th century myth of the Maya Hero Twins included in the Popol Vuh.

Gallery

References

External links

• Primate Info Net Alouatta Factsheets
• Howler monkey audio recording
• Information about howler monkeys from Belize Zoo (photos, video and audio included)
• "The Loudest Animal in the New World," Smithsonian National Zoological Park