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Alouatta caraya - Black Howler Monkey 

Courtesy of Honolulu Zoo

Physical Description:

Adult black howler monkeys are sexually dimorphic.  Males have a black pelage and females a tan pelage.  At birth, both sexes have yellow to reddish pelage which they retain until they reach 54 months (Redford and Eisenberg 1992).  Males weigh 6.5 kg and females 4.5kg (Robinson and Redford 1986, Redford and Eisenberg 1992).  The lower mandibles and hyoid bone are enlarged to form a resonate chamber, which is covered by their large beard (Mowes et al. 1989).  They have a strong prehensile tail, which lacks hair on the underside.  Tail length is 53.1-65 centimeters. The dental formula for Alouatta caraya is 2/2-1/1-3/3-3/3 = 36.  Alouatta is the only genus of platyrrhine with trichromatic color vision (Jacobs et al. 1996).


Alouatta caraya is found in southern Brazil, western Paraguay and the Pilcomayo River region, Bolivia, and the Salta, Chaco, Formosa, Santa Fe and Misones provinces of northern Argentina.  Specifically they are found in the xeric regions of the Chaco and in forested areas along the Paraguay and Pilcomayo rivers.  Robinson and Redford (1986) found Alouatta caraya at a density of 42.2/km2.  Density is a function of body size.

Range of Black and Gold Howler Monkey

(courtesy of:

Ontogeny and Reproduction:

The average gestation period for Alouatta caraya is 187 days.  They give birth to a single offspring, which weighs 113 grams (Redford and Eisenberg 1992).  Parturition occurs during the dry season; August through October.  The mammaries are laterally-proximal to the axillary region.  Alloparental care is common among adults and juvenile females.  Bravo and Sallenave (2002) observed adoption on one occasion.  Black howler monkeys have a unique chromosome type of X1X2Y1Y2 (Mudry et al. 1998).   The average life span is 16 years but they can live up to 20 years in captivity. 

Ecology and Behavior:

Alouatta caraya are diurnal and live in single- and multi-male groups (Crockett and Eisenberg 1987).  Zunino et al. (2001) observed that as density, or troop size, increased, the sex ratio remained the same.  Redford and Eisenberg (1992) estimated average troop size at seven black howlers.  The largest male in the troop is the dominant member.  Alouatta caraya primarily lives in the upper and middle strata of the forest canopy, but they can be found at all levels in some habitats. The activity budget of Alouatta caraya is 56.5% rest, 18.9% feeding, 10.5% travel, 2% confrontations, 6% general movement, and 6% social interactions.  Social interactions are a mixture of allogroming and play.  Play occurs at all age levels and is the most significant of all social interactions (Bravo and Sallenave 2002).  Mating always occurs within the troop.  Tongue-flicking is a behavior commonly associated with mating.
The monkeys are territorial and commonly use scent marking to set boundaries.  Home range size is 1.7-2.2 hectares and 76-82% of that area is actively defended through vocalization and confrontation (Bravo and Sallenave 2002).   High density promotes a smaller home range size.  If energy is not limited, activity levels will increase, as will the probability of confrontations as howlers expand into the distal portions of their home ranges (Bravo and Sallenave 2002).
Alouatta caraya are folivorous-frugivorous and are able to break down the tannins in leaves with their large salivary glands (Milton 1987, Bravo and Sallenave, 2002).  Their diet depends on mature leaves in July and shifts to mature fruits by November. There is a direct association between the density of howlers and density of fruiting trees (Zubino et al. 2001). They obtain water through leaves.  Black howlers have been observed "drinking" by licking their hands when succulent leaves are not available.


T. callithricis is a parasite found to infect 9.8% of black howler monkeys (Prieto et al. 2002).  

Black howlers are listed as a Cites Appendix II species.

Literature Cited:

Bravo, S. P. and A. Sallenave.  2002.  Foraging behavior and activity patterns of Alouatta caraya in thenortheastern Argentinean flooded forest. International Journal of Primatology 24(4):825-845.

Crocket, C. M. and J. F. Eineberg.  1987.  Howlers: variation in group size and demography.  In Smuts, B. B., D. L. Cheney, R. M. Seyfarth, R. W. Wrangham and T. T. Struhsaker (eds.) Primate Societies. University of Chicago Press, Chicago IL. pp. 54-68.

Jacobs, G. H., M. Nietz, J. F. Deegan, J. Neit and D. Neit.  1996.  Tricromatic colour vision in new world monkeys.  Nature (382):156-158.

Milton, K.  1987.  Physiological characteristics of the genus Alouatta.  International Journal of Primatology 8:428.

Mowes, M. A., R. A. Ojedoi and R. M. Berquez.  1989.  Guide to Mammals of Salta Province, Argentina.

Mudry, M. D., M. Rahn, M. Gorostiaga, A. Hick, M. S. Merani and A. J. Solari.  1998.  Revised karyotype of Alouatta caraya (Primates: Platyrrhini) based on synaptonemal complex and banding analyses. PubMed 128(1):9-16.

Prieto, O. H., A. M. Santa Cruz, N. Scheibler, J. T. Borda and L. G. Gómez.  2002.  Incidence and external morphology of the nematode Trypanoxyuris (Hapaloxyuris) callithricis, isolated from black-and-gold howler monkeys (Alouatta caraya) in Corrientes, Argentina.  Laboratory Primate Newsletter 41:3.

Redford, K. H. and J. F. Eisenberg.  1992.  Mammals of the Neotropoics: the southern core, Volume 2. University of Chicago Press, Chicago.

Robinson, J. G. and K. H. Redford.  1986.  Body size, diet and population of neotropical mammals.  The American Midland Naturalist 128(5):665-680.

Zunino, G. E., V. Gonzalez, M. M. Kowalewski and S. P. Bravo.  2001.  Alouatta caraya relations among habitat density and social organization.  Primate Report 61: 37-45.

Reference written by Michael Uffenbeck, Biol 378 (Mammalogy), University of WisconsinStevens Point:  Edited by Chris Yahnke. Page last updated July 25, 2005.
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