Red Howler Monkey

Taxonomic Classification:

Class: Atelidae

Genus: Alouatta

Species: A. seniculus

Common Name:

Red Howler Monkey

Physical Description

  • Male Height: 52.3 to 57 centimeters
  • Female Height: 46-57 centimeters
  • Male Weight: 6 – 7.6 kg
  • Female Weight: 4.5 – 6.3 kg
  • Fur is medium length and reddish-brown
    • Fur color can change with age
  • Extremely long arms and legs
  • Strong hands, with three opposable fingers
  • Strong feet
  • Eyes are usually dark-colored
  • A long, prehensile tail
    • Usually between 45 cm and 75 cm long
  • Males have a slight beard
  • Dental formula: 2-1-3-3
  • Brain size: 50.4 grams
  • Large neck and lower jaw
    • They have a prominent hyoid bone, with allows them to give their famous loud calls

Geographic location and range of the species:

  • Mainly found in Central and South America
    • Countries that Red Howler monkeys gather and live in are: Bolivia, Paraguay, Argentina, Brazil, Columbia, Ecuador, French Guina, Guyana, Peru, Suriname, and Venezuela
    • Likes tropical forests and mixed deciduous forest
    • Both arboreal and terrestrial
      • Arboreal mean “living in trees”
        • Prefers the upper and middle canopies of trees
        •  Prehensile tail, strong hands with opposable thumbs, and strong feet help the Red Howler monkey grasp onto branches
        • Preferred method of travel
  • Terrestrial means “living on the ground”
    • They are quadrupedal walkers and runners
    • Travel is slower through this method
    • Red Howler monkeys only cover 400m per day
    • The monkeys are most active in the morning and evening, while they spend their days resting and their evenings sleeping


  • Primarily vegetarian (Moynihan 62).
    • Gathers food primarily at dawn
    • Mainly consume leaves (folivorus), which is 40% of its diet
  • Eats buds, flowers, nuts, seeds, fruits (such as figs), and dirt
  • Occasionally small insects or animals may be eaten if they are caught by the slow-moving howler monkey, yet the howler is generally considered a herbivore (although scientifically he is an omnivore)
  • Pro for being a leaf-eater
    • You can find food everywhere
    • Cons for being a leaf-eater
      • Leaves give you little sugar and nutrients, and thereby give you little energy
      • However, howler monkeys can conserve the energy they are given by…
        • moving slowly
        • giving loud calls to announce the presence of troops instead of fighting for territory
        • sleeping for half the day
          • over 15 hours!

Social Organization:

  • Groups of Red Howler monkeys are called “troops”
    • They live in troops of 5-40 monkeys
      • On average, there are 10 monkeys in a single troop
  • One troop will be run by a dominant male
    • His job is to lead his troop in search of food
    • There will only be 1-2 males in a single troop
  • Male and female Red Howler monkeys can mate with a number of other Red Howler monkeys of the opposite sex
    • This is called “polygamy”
    • However, there are fierce sexual battles within and between troops
  • Young male bachelors are expelled from their original troops. They are forced to infiltrate another troop. In doing so, the male kills all the offspring in the new troop so he doesn’t have to take care of another monkey’s child, and so he can be assured that his genes will survive
    • Only 25% of infants survive such brutal attacks, even though mothers do protect their children
    • The Red Howler monkeys give their loud calls to announce the presence of one troop to any troops in the area
      • They do this so troops don’t fight for territory and food sources
      • They also do this so a single troop does not eat all the food from a single food source.


  • Seasonality of birth: Red howlers can give birth at any time during the year
    • During the wet season however, the number of births decreases.
    • Gestation length: 6 months
    • Number of infants/litters: one
    • Time between pregnancies: Two years
    • Age of sexuality maturity : four to eight years
    • Estrus swellings: 16 to 20 days and the female is receptive for 2 to 4 days
    • Age at weaning: 18 to 24 months
    • Time period infants stay with mothers: At least one year. Once the infant is a month old, the infant used its tail to hold on to its mother and gets little to no assistance.

Parental Care

  • Evidence of infanticide
    • When the alpha male gets beaten by a younger male, the younger male will take over the troop and kill all of the offspring that are not his own.
    • What is the father/infant relationship: Obviously, the father’s primary concern is to make sure that his genes continue after he dies. However, once he’s the leader of the tribe, he does eventually allow children to climb on top of him.
      • Essentially, he tolerates them.
    • The females without infants usually are very interested in the infants and allow them to climb on them

Language/ Communication Abilities

  • All Howler Monkeys are famous for their loud calls
    • They calls can carry out for over three miles!
    • Create the calls through the use of a specialized bone call the hyoid bone, which acts as a resonator
    • Usually the males have louder voices than females
    • These calls are multi-functional
      • They howl and whoop to announce that another troop is on their territory
        • This preserves the monkey’s much-needed energy, as they prevent fights over territory
        • warn against danger

Evidence of Culture:

Unfortunately, we found no known evidence of culture.

Interesting fact:

  • Live for about 15-20 years
  • Red Howler monkeys are amazing swimmers!


Here’s a picture of a happy Red Howler monkey sitting in a tree. This photo was taken by Bird Brian on August 31, 2009.

(Link to image):

This little howler monkey is taking a little nap…or is he? Kuba Bogaczewicz owns this photograph, which was taken on August 15, 2009.

(Link to picture):


Want to hear a red howler monkey’s call? Go to this video by randomsquiggle:

Or if you want to see what it’s like to walk around a forest and hear the howler monkeys’ calls, watch this video by halcyonhigh:


Ferrari, Stephen F., Liza M. Veiga, and Bernardo Urbani. “Geography in New World Monkeys (Platyrrhini): Ecological and Geographic Patterns.” Folia Primatologica. 79.5. (2008): 402-416.

Gron, K.J. “Primate Factsheets: Red holwer (Aluatta seniculus) Taxonom, Morphology & Ecology.” Primate National Primate Research Center, University of Winsconsin – Madison, 26 November 2007. 4 February 2011.>.

Lopez, Gabriela Orihuela, John Terborgh, and Natalia Ceballos. “Food selection by a hyperdense population of red howler monkeys (Alouatta Seniculus).” Journal of Tropical Ecology 21 (2005): 445-450.

“Monkeys, Apes and Humans.” 4 Feb. 2011. <>.

“Monkey (Red Howler).” Young People’s Trust for the Environment. 3 February 2011. <>.

Moynihan, Martin. The New World Primates. Princeton, NJ: Princeton University Press, 1979.

Napier, J.R., and P.H. Napier. A Handbook of Living Primates. New York: Academic Press, 1967.

“New World Monkeys.” Natural History Collection. 4 February 2011. <>.

Normile, Rebecca V. “Alouatta seniculus.” Animal Diversity Web. 2001. University of Michigan Museum of Zoology, 4 February 2011.  <>. Oxford University Press. November 2010. 5 February 2011. <>.

Radetsky,  Peter. “Gut Thinking.” Discover. 1 May 1995. 8 Feb 2011. <>.

“Red Howler Monkey (Alouatta Seniculus).” The Primata (Primates: Prosimians, Monkeys, and Apes). Web. 04 Feb. 2011. <>.

“Red Howler Monkey.” WildMagazine.Ca. Web. 04 Feb. 2011. <>.

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3 Responses to Red Howler Monkey

  1. megan says:

    A few things, mostly organizational.

    1) Can you put your material in the same order as it was on the assignment? That way each fact sheet follows the same pattern, and one person can search quickly for different types of info

    2) Watch which categories you BOLD and which you do not – you are putting some of the major and minor topics in bold, again making it hard to find info. Make sure to use the main titles of the categories (i.e. ‘Evidence of Culture’) for easy searching from one fact sheet to another.

    3) Bullet points would probably help to separate out different sub-facts

    4) Citations – since it is a fact sheet, you do not need to put the citation for each piece of information right next to it (if this was a paper you’d be great though!). And you can also synthesize these pieces of information together. Instead of one line defining folivore and another saying the monkey eats 40 % leaves, combine this to say ‘RHM are folivores that make up 40% of their diet eating leaves. Again, there is just so much information in so many places that it is hard to pick out the information quickly.

    4a) Citations – you just need to cite the OED once, and not list all the words you looked up.

    Generally, the data is good info. I think you are missing a few bits in the physical description (brain size/dentition).

  2. megan says:

    oh one other thing, for the tzxonomic classification, use the terms Class, Genus and Species next to each of the terms specific to your monkey, for context (Class: Atilidae)

  3. Question: I’ve checked three sites and it says Atilidae is the family, Alouatta the genus, and seniculus the species. Would you rather we used class instead of family?
    (Source of my information: .)

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