Editing Howler monkey (section)

==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 hyoids and is positively correlated with testes size. [[File:2006-08-08 Brüllaffe mit Jungtier, Monteverde (Costa Rica).jpg|thumb|200px|right|A Red Howler with child in [[Monteverde]] Cloud Forest Biological Reserve]] This results in two distinct groups, wherein one male with a larger hyoid and smaller testes copulates exclusively with a group of females, suggesting precopulatory vocal competition. The other group has more males, which have smaller hyoids, and larger testes. The larger the number of males, the smaller the hyoid, and the larger the testes.<ref name=":1" /> Female howler monkeys breed with multiple males within their group, with males in neighboring groups, and with solitary males. Central males tie up fellowship with cycling females.<ref>{{Cite book |last1=Kowalewski |first1=Martín M |url=https://books.google.com/books?id=RnK1BQAAQBAJ&dq=Howler+monkeys%3A+behavior%2C+ecology%2C+and+conservation.+Springer.&pg=PR5 |title=Howler monkeys: behavior, ecology, and conservation |last2=Garber |first2=Paul A |last3=Cortés-Ortiz |first3=Liliana |last4=Urbani |first4=Bernardo |last5=Youlato |first5=Dionisios |publisher=Springer |year=2014 |pages=10–11|isbn=9781493919604 }}</ref> 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, but 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]]
{{listen|filename=Howler monkey.ogg|title=Howler monkey growls|description=Unidentified species in [[Petén Department]], [[Guatemala]]|format=[[ogg]]}}
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. Their main vocals consist of loud, deep, guttural growls or "howls". Howler monkeys are widely considered to be the loudest land animals. 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| access-date=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. Howlers call usually when they are in areas with major feeding sites, which in some sort lead to advertise major feeding sites and their willingness to defend locally available fruit trees. Black howler monkeys incorporate information on resource availability along with neighbors’ current location. And the abundance of flowers are found to be an important factor that influenced behavior. Neighbors are more likely to move towards these calls when resource are scarce, and the reverse is true.<ref>{{Cite journal |last1=Van Belle |first1=Sarie |last2=Estrada |first2=Alejandro |date=2020-04-01 |title=The Influence of Loud Calls on Intergroup Spacing Mechanism in Black Howler Monkeys (Alouatta pigra) |url=https://doi.org/10.1007/s10764-019-00121-x |journal=International Journal of Primatology |language=en |volume=41 |issue=2 |pages=265–286 |doi=10.1007/s10764-019-00121-x |s2cid=209481526 |issn=1573-8604|url-access=subscription }}</ref>

===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, chicken coops, and consume the eggs.<ref name="BBC Earth News">{{cite web |url=http://news.bbc.co.uk/earth/hi/earth_news/newsid_8270000/8270801.stm |title=Monkeys 'reject vegetarianism'|last1=Walker |first1=Matt|access-date=3 September 2022|date=30 September 2009|website=Earth News |publisher=[[BBC]]}}</ref> When in smaller groups (up to twelve individuals) and low rainfall (up to {{cvt|2200|mm}}), they are more frugivorous. In larger groups and increased rainfall, frugivory decreases as a result of competition and fast food depletion.<ref>{{cite book |last1=Dias |first1=Pedro Américo D. |chapter=Diets of Howler Monkeys |date=2015 |chapter-url=https://doi.org/10.1007/978-1-4939-1960-4_2 |title=Howler Monkeys: Behavior, Ecology, and Conservation |pages=21–56 |editor-last=Kowalewski |editor-first=Martín M. |place=New York, NY |publisher=Springer |language=en |doi=10.1007/978-1-4939-1960-4_2 |isbn=978-1-4939-1960-4 |access-date=2022-11-30 |last2=Rangel-Negrín |first2=Ariadna |editor2-last=Garber |editor2-first=Paul A. |editor3-last=Cortés-Ortiz |editor3-first=Liliana |editor4-last=Urbani |editor4-first=Bernardo}}</ref> As they digest fruit, more than 90% of the fruits' seeds are excreted without damage, which results in seed dispersal and distribution in tropical forests.<ref>{{cite book |last1=Cortés-Ortiz |first1=Liliana |chapter=The Taxonomy of Howler Monkeys: Integrating Old and New Knowledge from Morphological and Genetic Studies |date=2015 |chapter-url=https://doi.org/10.1007/978-1-4939-1957-4_3 |title=Howler Monkeys: Adaptive Radiation, Systematics, and Morphology |pages=55–84 |editor-last=Kowalewski |editor-first=Martín M. |place=New York, NY |publisher=Springer |language=en |doi=10.1007/978-1-4939-1957-4_3 |isbn=978-1-4939-1957-4 |access-date=2022-12-02 |last2=Rylands |first2=Anthony B. |last3=Mittermeier |first3=Russell A. |editor2-last=Garber |editor2-first=Paul A. |editor3-last=Cortés-Ortiz |editor3-first=Liliana |editor4-last=Urbani |editor4-first=Bernardo}}</ref>

=== Sleeping ===
Howlers use the upper-middle part of their sleeping tree and use large branches on the 70% of nights that potentially allow for grouped sleeping or resistance to weather conditions and risk of branch breaking. Their sleeping sites are  usually close to  morning feeding sites.<ref>{{cite journal |last1=Brividoro |first1=M.V |last2=Kowalewski |first2=M.M |last3=Scarry |first3=C.J |year=2019 |title=Patterns of Sleeping Site and Sleeping Tree Selection by Black-and-Gold Howler Monkeys (Alouatta caraya) in Northern Argentina. |url=https://doi.org/10.1007/s10764-019-00094-x |journal=Int J Primatol |volume=40 |issue=2019 |pages=374–392|doi=10.1007/s10764-019-00094-x |s2cid=190648043 |url-access=subscription }}</ref>