Alouatta seniculus characteristics, habitat, feeding, reproduction

Jonah Lester

Alouatta seniculus or red howler monkey is a primate that belongs to the Atelidae family. This species is characterized by having a red coat, with golden or orange hues. The ventral area is darker and the beard area is brown or black. In relation to the face, it is black.

Another aspect that characterizes it is its howl. This has a strong intensity and can last up to eight seconds. These particularities are related to the hyoid bone. This bone structure is large and acts as an amplifier and resonator for the powerful vocalizations of the primate..

Red howler monkey. Source: Brian Ralphs [CC BY (]

The Alouatta seniculus it is widely distributed in the neotropical regions of South America. In these areas, it inhabits seasonal floodplain forests, humid forests and transitional forests, among others..

Article index

  • 1 Social organization
  • 2 General characteristics
    • 2.1 Size
    • 2.2 Fur
    • 2.3 Hyoid bone
    • 2.4 Locomotion
    • 2.5 Voice communication
  • 3 Conservation status
  • 4 Habitat and distribution
  • 5 Food
  • 6 Playback
    • 6.1 The hatchlings
  • 7 References 

Social organization

The red howler monkey is socially organized in herds, the size of which can vary depending on the habitat. Within groups of males, there is a hierarchy. Thus, the strongest is the alpha, which dominates over the other males and is the only one that can reproduce..

As for the fights for the establishment of leadership, they are usually violent, causing serious injuries in the opponents.

Both sexes emigrate from their natal group, but they do so in different proportions. Thus, between 70 and 80% of females reproduce far from the group where they were born, while, in males, this figure is approximately 98%.

In addition, a large part of the females migrate when they are 2 to 4 years old and the males do so between 4 and 6 years..

General characteristics


The Alouatta seniculus It presents sexual dimorphism, being the females smaller than the males. Thus, these have a body mass that ranges from 6 to 8 kilograms and the length of the body is 49 to 72 centimeters. In relation to the females, they measure between 46 and 57 centimeters, with a weight of 4.5 to 5.5 kilograms.

The tail of this primate is prehensile, and may be longer than the head and body. Generally, this structure averages 65.5 centimeters.


This species is identified by its fur, which can be red, with orange or gold tones. The ventral region is much darker than the dorsal. The area of ​​the face has little fur and has a bluish-black hue. As for the beard area, it can be black or brown.

Between the female and the male there are no differences with respect to coloration. However, the coat may turn darker, an aspect that is related to climatic variations and the geographic location of the animal..

Hyoid bone

The hyoid bone is located in the anterior region of the neck, below the tongue and above the thyroid cartilage. This has a horseshoe shape and is large, much larger than that of other howler primates. In addition, that of males is larger than that of females.

This bone structure works as a resonator for the sounds emitted by the primate. In addition, it contributes to deepening the tone of the calls and to amplify the vocalizations typical of the species.


The Alouatta seniculus it has arboreal and terrestrial habits. In this species, tripedalism and bipedalism are less frequent than quadrupedism. Because of this, when moving from one place to another, it usually does so in a slow quadruped.

As for suspension postures, they usually occur during feeding and very rarely while the animal is at rest. This mammal is capable of swimming and crossing rivers with moderate flows.

Vocal communication

The red howler monkey is characterized by its loud howls, which can last up to eight seconds. Calls are classified as short and long. The short ones are low-pitched, harsh barks, which are emitted rhythmically.

As for the long ones, they are loud roars that are vocalized together with another member of the group. These sounds can be heard up to a kilometer away.

Also, they can be issued to keep males away from another herd, who try to enter the group, or in the case of an intra-group situation..

In general, calls are used to communicate the distance and composition of the cluster. In relation to the howl of the female, he uses it to incite competition between the males.

State of conservation

Even though the Alouatta seniculus can adapt to living in small areas of the forest, its populations are affected by various factors. This has caused the decline of the communities, which is why the IUCN includes this mammal in the list of species at risk of extinction.

The main threat that afflicts this species is the degradation and loss of habitat, caused by the actions of man. Among the agents that negatively influence the environment are the construction of dams, the felling of forests and oil exploitation..

On the other hand, the red howler monkey is one of the most hunted primates in the Neotropics. However, this may vary between different geographic areas..

For example, in the western Amazon of Brazil, those that live in flooded forests are frequently caught during the high tide season. This is because flooded land prevents regular fishing activities..

Poaching is carried out to commercialize hyoid meat and bone. Medicinal properties are attributed to it in the treatment against goiter.

With regard to protective actions, this South American placental mammal is included in Appendix II of CITES.

Habitat and distribution

The Alouatta seniculus it is distributed in the neotropical regions of South America. In general, it is extended from the northwest of Colombia to the south and east of the Amazon River, in Brazil.

In addition, it is found in the eastern area of ​​the Andes, on the western coast of South America, from Colombia, through Peru, Bolivia and Brazil, to the Juruá and Purús rivers..

The red howler monkey lives in a wide variety of forests, including humid, tropical, low mountain, cloudy, swamp, transitional, and seasonally flooded..

An example of the widespread use of habitats occurs in Colombia. In that country, the species lives at high altitudes, being absent in the forests near the formation of alpine trees.

Although this primate is capable of adapting and occupying various types of forest formations, there are some exceptions. In this sense, in the Amazon, it is not located in areas of more than 1.8 kilometers inland, preferring the areas near lakes or the edges of rivers.


The red howler monkey is herbivorous, consuming mainly fruits and leaves. Also, the diet is supplemented with roots, seeds, flowers, berries, tree bark and leaf shoots..

In the natural habitat of this mammal, the availability of fruits is seasonal. As a result, the diet varies throughout the year. Consequently, in some seasons the species may be predominantly folivorous, while in others it is frugivorous..

Within the wide range of fruits, they prefer those of medium or large size, which have a juicy pulp. Also, they have a predilection for young leaves, rather than mature ones..

The teeth of the Alouatta seniculus they are adapted for the intake of fibrous leaves and stems. In this sense, the incisors help to cut the plant material and the molars, which have sharp ridges, help to chew food.

On the other hand, in the posterior intestine there are bacteria responsible for degrading cellulose, which is part of the walls of plant cells..


In this species, the female can reproduce between 4 or 5 years, while the male sexually matures when he is approximately 7 years old. Experts point out that the estrous cycle lasts 29.5 days. The female may show some external signs of estrus, although these generally go unnoticed.

The reproduction system of the red howler monkey is polygynous, where the alpha male has almost exclusively access to the females of the herd. However, extragroup matings can occur. In these, the females can join with the male of another group, in addition to doing it with the leader of their group.

Before copulating, and during the act, the couple can click their tongue, inspect and smell the genitals and lick each other's body. Then the male mounts the female from the back, as if covering her with his body.

The Alouatta seniculus does not breed seasonally. However, there are months in which a greater number of births occur. For example, the species that inhabit Peru reproduce all year round. However, most of the young are born between October and April and from June to September there are fewer births..

The babies

Gestation lasts about 191 days. The newborn has closed eyes and the coat shows a pale coloration. In general, females, both immature and adult, spend a long time near the young.


  1. Gron KJ. (2007) Primate Factsheets: Red howler (Alouatta seniculus) Taxonomy, Morphology, & Ecology. Retrieved from
  2. Wikipedia (2020). Venezuelan red howler. Recovered from
  3. Normile, R. (2001). Alouatta seniculus. Animal Diversity Web. Recovered from
  4. James Rossie (2002). Alouatta seniculus. Digital Morphology. Recovered from
  5. Boubli, J.-P., Di Fiore, A., Rylands, A.B., Mittermeier, R.A. (2015). Alouatta seniculus ssp. puruensis. The IUCN Red List of Threatened Species 2015. Recovered from
  6. Julliot, Sabatier (1993). Diet of the red howler monkey (Alouatta seniculus) in French Guiana. Recovered from

Yet No Comments