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'{{Automatic taxobox | name = Howler monkey<ref name=msw3>{{MSW3 Groves|pages=148–152|id=12100374}}</ref> | image = Alouatta guariba.jpg | image_caption = [[Brown howler]] | parent_authority = [[Édouard Louis Trouessart|Trouessart]], 1897 (1825) | taxon = Alouatta | authority = [[Bernard Germain Etienne de la Ville, Comte de Lacepede|Lacepede]], 1799 | type_species = ''[[red-handed howler|Simia belzebul]]'' | type_species_authority = [[Carl Linnaeus|Linnaeus]], 1766 | subdivision_ranks = Species | subdivision = ''[[Alouatta arctoidea]] <br/> [[Alouatta belzebul]] <br/> [[Alouatta caraya]] <br/> [[Alouatta coibensis]] <br/> [[Alouatta discolor]] <br/> [[Alouatta guariba]] <br/> [[Alouatta juara]] <br/> [[Alouatta macconnelli]] <br/> [[Alouatta nigerrima]] <br/> [[Alouatta palliata]] <br/> [[Alouatta pigra]] <br/> [[Alouatta puruensis]] <br/> [[Alouatta sara]] <br/> [[Alouatta seniculus]] <br/> [[Alouatta ululata]]'' | synonyms = '''''Mycetes''''' <small>Illiger, 1811</small><br/> '''''Stentor''''' <small>É. Geoffroy, 1812</small> | range_map =Alouatta range map.png | range_map_caption = Howler monkeys distribution }} '''Howler monkeys''' ([[genus]] '''''Alouatta''''' [[monotypic]] in [[subfamily]] '''Alouattinae''') are among the largest of the [[New World monkey]]s. They are famous for their loud howls, which can travel three miles through dense rain forest. These monkeys are native to [[South America|South]] and [[Central America]]n forests. Threats include human predation, [[habitat destruction]] and [[captivity (animal)|capture]] for pets or zoo animals. Fifteen [[species]] are recognized. Previously classified in the [[family (biology)|family]] [[Cebidae]], they are now placed in the family [[Atelidae]]. ==Classification== * ''A. palliata'' group ** [[Coiba Island howler]], ''Alouatta coibensis'' *** ''[[Alouatta coibensis coibensis]]'' *** [[Azuero howler]], ''Alouatta coibensis trabeata'' ** [[Mantled howler]], ''Alouatta palliata'' *** [[Ecuadorian mantled howler]], ''Alouatta palliata aequatorialis'' *** [[Golden-mantled howler]], ''Alouatta palliata palliata'' *** [[Mexican howler monkey]], ''Alouatta palliata mexicana'' ** [[Guatemalan black howler]], ''Alouatta pigra'' * ''A. seniculus'' group ** [[Ursine howler]], ''Alouatta arctoidea'' ** [[Red-handed howler]], ''Alouatta belzebul'' ** [[Spix's red-handed howler]], ''Alouatta discolor'' ** [[Brown howler]], ''Alouatta guariba'' *** [[Northern brown howler]], ''Alouatta guariba guariba'' *** [[Southern brown howler]], ''Alouatta guariba clamitans'' ** [[Juruá red howler]], ''Alouatta juara'' ** [[Guyanan red howler]], ''Alouatta macconnelli'' ** [[Amazon black howler]], ''Alouatta nigerrima'' ** [[Purus red howler]], ''Alouatta puruensis'' ** [[Bolivian red howler]], ''Alouatta sara'' ** [[Venezuelan red howler]], ''Alouatta seniculus'' ** [[Maranhão red-handed howler]], ''Alouatta ululata'' * ''A. caraya'' group ** [[Black howler]], ''Alouatta caraya'' ==Anatomy and physiology== [[File:Allouataadulto 500px.jpg|thumb|upright|left|Male [[mantled howler]]]] Howler monkeys have short snouts and wide-set, round nostrils. Their noses are very keen, and they can smell out food (primarily fruit and nuts) up to 2&nbsp;km away. Their noses are usually roundish snout-type, and the nostrils have many sensory hairs growing from the interior. They range in size from {{convert|56|to|92|cm|in|abbr=on}}, excluding their tails, which can be equally as long, in fact in some cases the tail has been found to be almost five times the body length. This is a prime characteristic. Like many New World monkeys, they have [[prehensile tail]]s, which they use for picking fruit and nuts from trees. Unlike other [[New World monkey#Characteristics|New World monkey]]s, both male and female howler monkeys have [[trichromat]]ic color vision.<ref>{{cite journal|last=Jacobs|first=G. H.|author2=Neitz, M. |author3=Deegan, J. F. |author4=Neitz, J. |year=1996|title=Trichromatic colour vision in New World monkeys|journal=Nature|issue= 6587|pages=156–158|doi=10.1038/382156a0|volume=382|pmid=8700203}}</ref> This has [[Evolution of color vision in primates|evolved independently]] from other New World monkeys due to [[gene duplication]].<ref name=Lucas2003>{{cite journal |author1=Lucas, P. W. |author2=N. J. Dominy | year = 2003 | title = Evolution and function of routine trichromatic vision in primates | journal = Evolution | volume = 57 |pages = 2636–43 | pmid = 14686538 | issue = 11 | doi=10.1554/03-168}}</ref> They have lifespans of 15 to 20 years. Howler species are dimorphic and can also be dichromatic (i.e. ''Alouatta caraya''). Males are, on average, 1.5 to 2.0&nbsp;kg heavier than females. The [[hyoid]] of ''Alouatta'' is [[Skeletal pneumaticity|pneumatized]], one of the few cases of postcranial pneumaticity outside the [[Saurischia]]. The volume of the hyoid of male howler monkeys is negatively correlated with the dimensions of their testes.<ref name=Dunnetal2015>{{cite journal |author1 = Dunn, J. C. |author2 =Halenar, L. B. |author3 =Davies, T. G. |author4 =Cristobal-Azkarate, J. |author5 =Reby, D. |author6 =Sykes, D. |author7 =Dengg, S. |author8 =Fitch, W. T. |author9 =Knapp, L. A. | year = 2015 | title = Evolutionary Trade-Off between Vocal Tract and Testes Dimensions in Howler Monkeys | journal = Current Biology | volume = 25 |pages = 2839–44 | issue = 21 | doi=10.1016/j.cub.2015.09.029 | pmid=26592343 | pmc=4635310}}</ref> ===Locomotion=== Howler monkeys generally move quadrupedally on the tops of branches, usually grasping a branch with at least two hands or one hand and the tail at all times. Their strong prehensile tails are able to support their entire body weight. Fully grown adult howler monkeys do not often rely on their tails for full body support, whereas juveniles do so more frequently. ==Behaviour== [[File:Alouatta sara (Bolivian red howler).jpg|thumb|200px|left|A [[Bolivian red howler]] (''Alouatta sara'')]] ===Social systems=== Most howler species live in groups of six to 15 animals, with one to three adult males and multiple females. Mantled howler monkeys are an exception, commonly living in groups of 15 to 20 individuals with more than three adult males. The number of males in a given group is inversely correlated with the size of their hyoid, and is positively correlated with testes size. This results in two distinct groups, wherein one male with a larger hyoid and smaller testes copulates exclusively with a group of females. The other group has more males, which have smaller hyoids, and larger testes, and free [[copulation (zoology)|copulation]] occurs among the group. The larger the number of males, the smaller the hyoid, and the larger the testes.<ref name=Dunnetal2015 /> Unlike most New World monkeys, in which one sex remains in natal groups, juveniles of both sexes emigrate from their natal groups,<ref name=Sussman>{{cite book | author = Sussman, R. | title = Primate Ecology and Social Structure, Vol. 2: New World Monkeys, Revised First Edition | pages = 142–145| publisher = Pearson Prentice Hall |date=July 2003 | isbn = 978-0-536-74364-0}}</ref> such that howler monkeys could spend the majority of their adult lives in association with unrelated monkeys. Physical fighting among group members is infrequent and generally of short duration. However, serious injuries can result. Both males and females rarely fight with each other, but physical aggression is even more rare between sexes.<ref name=Sussman/><ref>{{cite book |author = Crockett | chapter = Family Feuds | title = Primate Anthology, The: Essays on Primate Behavior, Ecology and Conservation from Natural History | pages = 32 |editor1=Ciochon, R. L. |editor2=Nisbett, R. A. | publisher = Prentice Hall | isbn = 978-0-13-613845-7 | date = 1997-10-02}}</ref> Group size varies by species and by location, with an approximate ratio of one male to four females.<ref name=Sussman/> ===Communication=== [[File:howler monkey.jpg|thumb|A pair of [[Alouatta caraya|black howler monkeys]] (''Alouatta caraya'') vocalising]] [[File:Howler monkey.ogg|Howler monkey growls]] As their name suggests, vocal [[Animal communication|communication]] forms an important part of their [[social behavior]]. They each have an enlarged basihyal or [[hyoid bone]], which helps them make their loud vocalizations. Group males generally call at dawn and dusk, as well as interspersed times throughout the day. The main vocals consist of loud, deep guttural growls or "howls". Howler monkeys are widely considered to be the loudest land animal. According to ''Guinness Book of World Records'', their vocalizations can be heard clearly for {{Convert|3|mi|km|abbr=on}}.<ref>{{Cite web | url=https://nationalzoo.si.edu/animals/black-howler-monkey | title=Black howler monkey| website=Smithsonian’s National Zoo & Conservation Biology Institute| date=4 April 2016| accessdate=12 February 2019}}</ref> The function of howling is thought to relate to intergroup spacing and territory protection, as well as possibly to mate-guarding. ===Diet and feeding=== [[File:Ursine howler monkey (Alouatta seniculus arctoide) 2.jpg|thumb|An [[ursine howler]]]] These large and slow-moving monkeys are the only [[folivore]]s of the New World monkeys. Howlers eat mainly top canopy [[leaf|leaves]], together with [[fruit]], buds, [[flower]]s, and [[Nut (fruit)|nut]]s. They need to be careful not to eat too many leaves of certain species in one sitting, as some contain [[toxin]]s that can poison them.<ref>{{cite journal | author = Glander, Kenneth E. | title = Poison in a monkey's Garden of Eden | journal = Natural History |date=March 1977 | pages = 146–151 | volume = 86|url=https://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/7016/77%20Glander%20poison.pdf?sequence=1}}</ref> Howler monkeys are also known to occasionally raid birds' nests and chicken coops and consume the eggs.<ref name="BBC Earth News">[http://news.bbc.co.uk/earth/hi/earth_news/newsid_8270000/8270801.stm], additional text.</ref> ==Relationship with humans== While seldom aggressive, howler monkeys do not take well to captivity and are of surly disposition. However, the [[black howler]] (''Alouatta caraya'') is a relatively common pet monkey in contemporary [[Argentina]] due to its gentle nature, in comparison to the [[capuchin monkey]]'s aggressive tendencies, in spite of its lesser intelligence, as well as the liabilities meant by the size of its droppings and the males' loud vocalisations. [[John Lloyd Stephens]] described the howler monkeys at the Maya ruins of [[Copán]] as "grave and solemn, almost emotionally wounded, as if officiating as the guardians of consecrated ground". To the Mayas of the Classic period, they were the divine patrons of the artisans, especially scribes and sculptors. They were seen as gods in some tribes, and the long, sleek tail was worshipped for its beauty. Copán in particular is famous for its representations of [[howler monkey gods]]. Two howler monkey brothers play a role in the myth of the [[Maya Hero Twins]] included in the [[Popol Vuh]], a widely feared tale of soul and passion. {{clear}} ==References== {{Reflist}} ==External links== {{Wikispecies|Alouattinae}} {{Wikispecies|Alouatta}} {{Commons category|Alouatta|howler monkeys}} * [http://pin.primate.wisc.edu/factsheets/links/alouatta Primate Info Net ''Alouatta'' Factsheets] * [http://www.monteverdeinfo.com/sounds/howler_monkey.mp3 Howler monkey audio recording] * [http://www.belizezoo.org/zoo/zoo/mammals/how/how1.html Information about howler monkeys from Belize Zoo (photos, video and audio included)] * [http://nationalzoo.si.edu/Animals/SmallMammals/Exhibits/HowlerMonkeys/LoudestAnimal/default.cfm "The Loudest Animal in the New World," Smithsonian National Zoological Park] {{Atelidae nav}} {{Taxonbar|from=Q504247}} [[Category:Folivores]] [[Category:Howler monkeys| ]] [[Category:Mammals of Guyana]] [[Category:Mammals of Honduras]]'