Howler monkeys are herbivores

Red howler monkey

The Red howler monkey (Alouatta seniculus) belongs to the family of capuchin-like monkeys (Cebidae) to the subfamily of howler monkeys (Alouattinae). It is considered to be the loudest primate species.


The taxonomy of the red howler monkey is considered controversial. According to Groves (2001) the species is divided into three subspecies. these are A. s. Arctoidea, A. s. Juara and A. s. Seniculus. Rylandset al. assumes 7 subspecies. these are A. s. Seniculus, A. s. Insulanus, A. s. Amazonica, A. s. Juara, A. s. Puruensis and A. s. Arctoidea and A. s. Stramineus. Groves leads A. s. Amazonica and A. s. Puruensis as A. s. Juara as well as and A. s. Insulanus as A. macconnelli.

Detection and differences

The red howler monkey is similar to the Bolivian howler monkey (Alouatta sara). The species can be distinguished from the red howler monkey due to the brick-red color and the darker extremities. The red howler monkey is also slightly smaller and lighter than the Bolivian howler monkey.


Appearance and dimensions

The red howler monkeys are among the heaviest New World monkeys. Females reach a body length of 46.8 to 49.7 cm, a tail length of about 65 cm and a weight of 4,500 to 6,300 g. Males reach a body length of 52.3 to 57.0 cm, a tail length of about 65 cm and a weight of 6,000 to 7,600 g. Females therefore remain smaller and lighter than males. Sex dimorphism varies between the populations with 69 and 95 percent of body weight. The tail reaches about the length of the body and serves the animals as a grasping organ. The fur is reddish to orange-red or golden-red in color. Ventrally, the overall color is darker, often reddish-brown to brown. The region around the mouth is also brown in color. The face itself is colored blue-black and has only sparse hair. There may be local variations in the color of the coat, but there are no differences in the color of the coat between the sexes. The distinctive features of the red howler monkey include the shape and size of the hyoid bone (Hyoid bone). The way it works mainly affects the pitch and the deep resonance. Red howler monkeys are among the loudest primates for a reason.

Way of life

Red howler monkeys are diurnal primates. However, there are clear seasonal differences in daily activity. In the dry season, the amount of sleep is significantly lower than in the rainy season. More time is invested in foraging for food in the rainy season. Overall, red howler monkeys spend almost half of the day resting and sleeping. The high proportion of rest breaks is related to the folivorous diet and the associated difficulties with the digestion of the leafy food. Since more fruit is eaten in the rainy season, the proportion of rest breaks in the rainy season decreases accordingly. Foraging and eating usually takes place in the morning and afternoon. Red howler monkeys spend the night in groups high up in the treetops. The territory of the red howler monkeys has a size of 0.1 to 1.8 km². It is assumed that the territories have a constant size. There are certainly overlaps between individual areas. When hiking through an area, a red howler monkey covers a distance of 980 to 2,200 m.

Social organization and behavior

The group size is variable with 6 and 10.5 (min / max 4 to 18) individuals and depends on the quality of the living space. A group can have one or more males, females 1 to 4. The males, led by a dominant alpha male, rule over the females within a group. An alpha male is usually larger and more powerful than a subordinate male. Sexually mature animals of both sexes usually leave the birth group when they reach sexual maturity. Males do this more often than females. Females are more likely to form new groups, while males usually join existing groups. Females leave the birth group at the age of 2 to 4 years, males at the age of 4 to 6 years. The territorial demarcation or communication between individual groups takes place via the characteristic roar. This is especially the case during the early hours of the morning. The alternate cleaning of the fur, the so-called allogrooming, occurs rarely and when it does, it is only for a short period of time. Allogrooming is mainly used for social purposes by the red howler monkeys. Every now and then it comes to quite violent fights between different groups, some of which result in serious injuries. Agonistic conflicts between the males of different groups, however, begin harmlessly with raising the fur (piloerection), roaring and hissing.


Red howler monkeys are mainly in trees, but they change these terrestrially from time to time. The main type of exercise is climbing, followed by four-legged walking and running. The movement is generally rather slow. In contrast to quadrupedia, bipedia is rarely observed. Due to the heavy weight of the red howler monkeys, gaps between trees are seldom bridged by jumping. When climbing, the tail serves as a grasping organ. Swimming was also observed, although the animals rarely swim across rivers.



Red howler monkeys occur in neotropical South America in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, on Trinidad and Tobago and in Venezuela. The distribution area thus extends from northern Colombia to the Amazon in Brazil. In east-west expansion, the distribution extends from the eastern Andes to the Atlantic coast. The nominate form Alouatta seniculus seniculus occurs from northern Colombia to Venezuela. Alouatta seniculus arctoidea is common along the coast of Venezuela. The occurrence of Alouatta seniculus juara extends over Brazil and large parts of Ecuador, Peru, Colombia and Venezuela. Alouatta seniculus macconnelli is proven in Trinidad and Tobago as well as in Guyana. Alouatta seniculus sara occurs in Bolivia. In large parts of the distribution area there are no clear boundaries between the individual subspecies.


Red howler monkeys live in a wide variety of habitats. Humid rainforests, but also mountain forests, secondary forests, swamps, alluvial forests, wooded river banks, moors, flood plains and dry forests are populated. In close proximity to humans, the animals can occasionally also be observed in cocoa plantations. Only forests in alpine locations are not populated. The species is considered to be detected at altitudes up to 3,200 m above sea level. Red howler monkeys are usually found in trees up to 29 cm in diameter. In the forage trees they can be found both high up in the canopy and in the lower layers. Due to the large distribution area and the large number of populated habitats, there are great differences in the amount of precipitation and mean daytime temperatures. In the montane rainforests in Colombia, at altitudes of 2,300 m above sea level, temperatures of 8.5 and 21 ° C and rainfall of 194.2 cm per year prevail.



Due to the large distribution area, the red howler monkey lives with numerous Primates (Primates). In relation to the competition for living space, these are particularly tamarins (Saguinus), Night monkeys (Aotidae), Sakis (Pithecia), Capuchin monkeys (Cebus), Spider monkeys (Ateles), Woolly monkeys (Lagothrix), Marmosets (Callithrix), Jumping monkeys (Callicebus), Uakaris (Cacajao) and Squirrel monkey (Saimiri). In food competition, the species is, for example, with the black spider monkey (Ateles paniscus). Beneath the fodder trees, numerous other animal species such as the white-tailed deer benefit (Odocoileus virginianus) from falling fruits.

Predators and Mortality

The harpy eagle is one of the natural enemies (predators) (Harpia harpyja). The harpy not only prey on juveniles, but also on adults. Near the forest floor, the jaguar (Panthera onca), the puma (Puma concolor), the ocelot (Leopardus pardalis), the Maikong (Cerdocyon thous) and even spectacled caimans (Caiman yacare) and idol snake (Boa constrictor) to the potential enemies.

Diseases and parasites

Diseases and parasites in red howler monkeys were identified by Phillipset al. (2004) examined. The species is particularly susceptible to intestinal parasites of the genera Strongyloides, Chilomastix, Trichuris, Blastocystis and Iodamoeba. Strongyloides and Trichuris count among the roundworms (Nematoda). The other genera are eukaryotic unicellular organisms. It is not known to what extent the intestinal parasites have a negative impact on the populations.


As the predominant herbivores, red howler monkeys eat frugivor and folivor, which means that pulp and leaves are high on the menu. The animals also rarely eat seeds, flowers, berries, stone fruits, leaf stalks, buds, roots and bark. Popular forage crops include figs (Ficus), Mulberry Family (Moraceae) of the genera Clarisia and Ogcodeia, Annonaceae (Annonaceae) how Xylopia as well as ant trees (Cecropia). The red howler monkeys especially like to eat larger fruits with juicy flesh. Young leaves are usually preferred on leaves. The species is an important part of the ecosystem for the spread of seeds of the plants. The food consumed fluctuates both locally and seasonally, as the availability of fruit is not constant in all regions. In these regions, red howler monkeys eat young leaves instead of ripe fruit. The animals are not dependent on drinking water, the water requirement is completely covered by the food they eat. Occasionally, red howler monkeys can be seen on salt licks and termite nests (Izawaet al. 1990).


When you roar

Sexual maturity is reached in females at the age of 4 to 5 years, males are only sexually mature at the age of a good 7 years. Both monogamous and polygamous reproductive systems occur in the red howler monkeys. In groups with more than one male, usually only the dominant male has unimpeded access to the females. If the dominance status changes in a group, it is not uncommon for the dominant male to kill the offspring. It is not uncommon for larger groups to migrate sexually mature females. Mating behavior between males and females includes, in particular, sniffing and licking the genitals and other parts of the body. The copulation itself is short-lived, with copulation occurring several times every hour. Red howler monkeys do not mate strictly seasonally, but peaks in births can be seen at certain times of the year. Most of the births occur in the beginning of the rainy season. The ovarian cycle in females is 29.5 days. After an average gestation period of 191 days, a female gives birth to a young. There are approximately 517 days between two births. As a rule, the offspring are born at night, and birth usually only takes a few minutes. Day births, on the other hand, are rare. Shortly after birth, a mother consumes the placenta. The young animal is poorly developed, sparsely hairy and blind. Only the mothers take care of the offspring. They also actively provide protection. In the first month of life, a young animal is carried by the mother on the stomach, later on the back. A young animal remains in close proximity to the mother until it is four months old. Later the young animals become more and more independent and explore the surrounding area. Independence is achieved between the 7th and 8th month of life. The suckling period ends a short time later. Life expectancy in the wild is unknown; in captivity, a red howler monkey can reach an age of up to 22 years.

Ecology, hazard and protection

Red howler monkeys are not yet an endangered species and are therefore listed in the IUCN Red List in the LC, Least Concern category. In the Washington Convention on the Protection of Species (CITES), the species is listed in Appendix II of the agreement. Red howler monkeys are extremely adaptable and can quickly adapt to changing environmental influences. The main threats today include the destruction of natural habitats, the fragmentation of the remaining habitats, human hunting and general pollution. In large parts of the distribution area, the destruction of natural habitats is proceeding in great strides. On the one hand, wetlands are being dried up, on the other hand, forests are being completely cut down. The main threats come from illegal logging, clearing for agricultural land and oil exploration. In Brazil and Venezuela, habitats have been destroyed by the construction of dams. In the entire Neotropical region, red howler monkeys are under more or less intense hunting pressure. The species is particularly popular with the indigenous people of Brazil. In coastal regions, environmental pollution, especially from oil pollution leaking from pipes and pipelines, is a major threat.


See also

Literature and sources

  • Thomas Geissmann: Comparative primatology. Springer Verlag, 2003, ISBN 3540436456
  • Ronald M. Nowak: Walker's Mammals of the World: v. 1 & 2. B&T, edition 6, 1999, (engl.) ISBN 0801857899
  • Don E. Wilson & DeeAnn M. Reeder: Mammal Species of the World, a Taxonomic & Geographic Reference. J. Hopkins Uni. Press, 3rd ed., 2005 ISBN 0801882214
  • David Macdonald: The great encyclopedia of mammals. Ullmann / tandem ISBN 3833110066
  • Hans Petzsch: Urania Animal Kingdom, 7 Vols., Mammals. Urania, Stuttgart (1992) ISBN 3332004999
  • Mammals. 700 species in their habitats. Dorling Kindersley, 2004. ISBN 383100580X

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