Venezuelan Red Howler
The Venezuelan red howler (Alouatta seniculus) is a South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

n species of howler monkey
Howler monkey
Howler monkeys are among the largest of the New World monkeys. Fifteen 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...

, a type of New World monkey
New World monkey
New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...

. It is found in the western Amazon Basin
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

 in Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

, Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

, Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

, Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

, Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

 and Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

. The population in the Santa Cruz Department
Santa Cruz Department
Santa Cruz, with an area of 370,621 km², is the largest of the nine constituent departments of Bolivia. In the 2001 census, it reported a population of 2,029,471. The capital is the city of Santa Cruz de la Sierra. The state is one of the wealthiest states in Bolivia with huge reserves of...

 in Bolivia was split off as a separate species, the Bolivian red howler
Bolivian Red Howler
The Bolivian red howler is a species of howler monkey, a type of New World monkey, endemic to Bolivia.-External links:* *...

, in 1985, and more recently it has been recommended splitting off the population in north-eastern South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 and Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...

 as the Guyanan red howler
Guyanan Red Howler
The Guyanan red howler is a species of howler monkey, a type of New World monkey, native to Suriname, Guyana, Trinidad, French Guiana and Brazil....

. All howler monkeys belong to the family Atelidae
Atelidae is one of the five families of New World monkeys now recognised. It was formerly included in the family Cebidae. Atelids are generally larger monkeys; the family includes the howler, spider, woolly and woolly spider monkeys...

 and the infraorder Platyrrhini (New World monkeys).


There is little sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

. The males range from 49-72 cm and females from 46-57 cm long. The males weigh between 5.4-9 kg
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

, while females are 4.2-7 kg. It has a long prehensile tail of approximately 49-75 cm. The tail is covered with fur except for the last third underside of the tail, which allows it to grab branches. The color of both males and females is a deep reddish-brown, and the color shade changes with age. Their faces are surrounded by fur and they have stubby noses.

The jawbone of the red howler monkey is large, especially the body of the mandible. The position of the foramen magnum is very posterior in the howler monkey, making way for the expanded jaw and enflated hyoid bone.
Howler monkeys also have an inflated bulla, which is the bony encasement of the middle ear. This makes them an exception among other New World monkeys.

Alouatta seniculus is an arboreal and diurnal primate that spends much of its time up high in the canopy. Its preferred method of locomotion is quadrupedal walking with minimal leaping. Their long, prehensile tails also assist them with this by providing both support and grasping abilities. In addition, their hands and feet have a grasping pattern that allows them to better move about in the trees. This can be seen in their hands by the wide separation of the second and third digits.

Social interactions

It lives in groups of 3 to 9 individuals (usually 5 to 7). The groups are polygynous
Polygamy is a marriage which includes more than two partners...

 with only one or two males and the rest females and their offspring. One male is the usually dominant monkey of the group, and he is responsible for leading them to new food sites and defending them. The females of the group are in charge of the offspring. Venezuelan red howlers are most active in the morning; this is when the group is on the move to find another feeding spot. The howlers are famous for their “dawn chorus”. These sounds are roaring and howling calls that are performed mostly by the males in the group. The roars can be heard up to 5 km away in the forest, and makes their presence known in the area. This is also used to prevent confrontations between groups, which will prevent energy loss by avoiding physical fighting. Because of their low-sugar diets, conservation of energy is key to their day. The calls also help in the scattering of the groups and lessens the competition over food.

Diet and dentition

Howler monkeys are folivores which means that their diet mainly consists of leaves, but they also rely on nuts, small animals, fruits, seeds, and flowers for important sources of nutrition. These foods provide sugar necessary for growth and energy for the monkeys. The most important part of their diet are leaves, which they can’t live without for more than a week. They eat both older and younger leaves; however, the older leaves provide more nutrition. The howler monkeys are able to eat their largely leafy diet of fibrous leaves due to the structural aspects of their dentition. Narrow incisors aid in the ingestion of the leaves, and molars with sharp, shearing crests help them to better chew their food. In addition, they have a complex stomach that aids in the digestive process. Their hindgut and large intestine also help with digestion. The hindgut contains bacteria that digest leaves and makes up a third of the Venezuelan Red Howler’s total body volume.

Like other New World monkeys, the Venezuelan red howler's dental formula (maxilla and mandible) is as follows: 2 Incisors, 1 Canine, 3 Premolars, 3 Molars.


There is fierce sexual competition between males due to an unbalanced sex ratio
Sex ratio
Sex ratio is the ratio of males to females in a population. The primary sex ratio is the ratio at the time of conception, secondary sex ratio is the ratio at time of birth, and tertiary sex ratio is the ratio of mature organisms....

. The females attract males by moving their tongue around in order to initiate mating. If the male does not respond, she moves on to another mate. The average gestation period is 190 days. The infant will stay with the mother for 18-24 months. After males reach sexual maturity they are expelled from their natal group. The male must then invade a foreign group. There, the male kills off the other leader and whatever offspring the first leader generated. By doing this, the male is killing any possible competition. Less than 25% of offspring survive male invasions.


There are traditionally three subspecies of this howler, though Stanyon et al. (1995) concluded that the number of chromosomal differences between A. s. sara and A. s. arctoidea (which resulted in A. s. sara being a considered a full species) was on a similar scale to that found between A. s. sara and A. s. seniculus by Minezawa et al. (1986).
  • Colombian red howler, Alouatta seniculus seniculus
  • Ursine howler
    Ursine Howler
    The Ursine howler is a species of howler monkey native to Venezuela, and possibly Colombia. It is sometimes considered a subspecies of the Venezuelan red howler and classified as Alouatta seniculus arctoidea....

    , Alouatta seniculus arctoidea
  • Juruá red howler
    Juruá Red Howler
    The Juruá red howler is a species of howler monkey, native to Peru, Brazil and possibly Colombia....

    , Alouatta seniculus juara

External links

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