User:Floudghi/Howler monkey

Article Draft

Lead

Howler monkeys (genus Alouatta, monotypic in subfamily Alouattinae) are the most widespread primate genus in the Neotropics and are among the largest of the platyrrhines along with the muriquis(Brachyteles ), the spider monkeys(Ateles) and woolly monkeys (Lagotrix). These monkeys are native to South and Central American forests. They are famous for their loud howls, which can travel more than one mile through dense rain forest. Males experience an evolutionary trad off between investments in precopulatory treats, larger Hyoids but smaller testes , or postoculatory traits, larger testes and smaller Hyoids. Fifteen species are recognized. Previously classified in the family Cebidae, they are now placed in the family Atelidae. They are primarily folivores but also highly frugivores, and act as seed dispersal agents through their digestive system and their locomotion. Threats include human predation, habitat destruction, and capture for pets or zoo animals.

Edit summary: I Added the sentences

" They are primarily folivores but also highly frugivores, and act as seed dispersal agents through their digestive system and their locomotion" and changed the overall organization of sentences.

" Males experience an evolutionary trad off between investments in precopulatory treats, larger Hyoids but smaller testes, or postoculatory traits, larger testes and smaller Hyoids.

Article body

Anatomy

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 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 56 to 92 cm (22 to 36 in), excluding their tails, which can be equally long; in fact in some cases the tail has been found to be almost five times the body length.^{[citation needed]} This is a prime characteristic. Like many New World monkeys, they have prehensile tails, which they use while picking fruit and nuts from trees. Unlike other New World monkeys, both male and female howler monkeys have trichromatic color vision. This has evolved independently from other New World monkeys due to gene duplication. They have lifespans of 15 to 20 years. Howler species are dimorphic and can also be dichromatic (i.e. Alouatta caraya). Males are typically 1.5 to 2.0 kg heavier than females.

Howler monkeys have a flat cranial shape due to a folivores diet and an advanced vocal system. Their brain growth is posteriorly rather than superiorly or inferiorly as in other platyrrhines. The hyoid of Alouatta is 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, and with the number of males per group. Larger hyoids decrease space between formant, and offers impression of larger body size.

Edit summary I added the sentence "and with the number of males per group. Larger hyoids decrease space between formant, and offers impression of larger body size."

Edit summary I added the sentence "Howler monkeys have a flat cranial shape due to a folivores diet and an advanced vocal system. Their brain growth is posteriorly rather than superiorly or inferiorly as in other platyrrhines"

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, but juveniles do so more frequently. A significant amount of their travel is done through the ground, with sitting and resting being their most frequent postures.

Edit summary " A significant amount of their travel is done through the ground, with sitting and resting being their most frequent postures."

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. 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[6]. The other group has more males, which have smaller hyoids, and larger testes, and free copulation occurs among the group. The larger the number of males, the smaller the hyoid, and the larger the testes It's suggested that The few males and multi-female group have the trad-off of larger hyoids rather than larger testes because competition over females is more vocally mediated as enlarged hyoid bones play the role of a weapon that increases the acoustic sound and impression of body size. In the case of increased males per group, it's found that the Hyoid volume decreases and testes volume increase for higher degrees of postcopulatory sperm competition. Unlike most New World monkeys, in which one sex remains in natal groups, juveniles of both sexes emigrate from their natal groups, such that howler monkeys could spend the majority of their adult lives in association with unrelated monkeys

Edit summary : I added the following sentences

-" suggesting precopulatory vocal competition"

-"The larger the number of males, the smaller the hyoid, and the larger the testes It's suggested that The few males and multi-female group have the trad-off of larger hyoids rather than larger testes because competition over females is more vocally mediated as enlarged hyoid bones the role of a weapon that increases acoustic sound and impression of body size. In the case of increased males per group, it's found that the Hyoid volume decreases and testes volume increase for higher degrees of postcopulatory sperm competition. "

-"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.

Communication[edit]

A pair of black howler monkeys (Alouatta caraya) vocalising

0:25 As their name suggests, vocal 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 3 mi (4.8 km). 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[4]

-Edit summary: " 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"

Diet and feeding[edit]

An ursine howler These large and slow-moving monkeys are the only folivores of the New World monkeys. Howlers eat mainly top canopy leaves, together with fruit, buds, flowers, and nuts. They need to be careful not to eat too many leaves of certain species in one sitting, as some contain toxins that can poison them. Howler monkeys are also known to occasionally raid birds' nests and chicken coops and consume the eggs. Howler monkey's feeding behavior are primarily highly folivores, but can also be highly frugivorous. They are more frugivores in conditions where rainfall is to a level up to 2200 mm and group size is not too large ( up to 12 Howler Monkeys). In forests where rainfall is higher than 2200mm, frugivory decreases as a result of competition and fast food depletion.[2] . They can swallow more than 90% of seeds and excrete them without damage, which result in seed dispersal and distribution in tropical forests.

Edit summary:" Howler monkey's feeding behavior are primarily highly folivores, but can also be highly frugivorous. They are more frugivores in conditions where rainfall level is up (up to 2,200 mm (87 in)) and when group size is up to 12 Howler Monkeys. In larger groups and increased rainfall, frugivory decreases as a result of competition and fast food depletion."

Edit summary added sections: " They can swallow more than 90% of seeds and excrete them without damage, which result in seed dispersal and distribution in tropical forests. "

Sleeping

Howlers use the upper-middle part of their sleeping tree and use large branches on 70% of nights which potentially allow for grouped sleeping or for resistance to weather conditions and risk of branch breaking. Their sleeping sites are usually close to morning feeding sites. [7]

References

[1]Seed Dispersal by Howler Monkeys: Current Knowledge, Conservation Implications, and Future Directions. In: Kowalewski, M., Garber, P., Cortés-Ortiz, L., Urbani, B., Youlatos, D. (eds) Howler Monkeys. Developments in Primatology: Progress and Prospects. Springer, New York, NY. https://doi.org/10.1007/978-1-4939-1960-4_5

[2]Dias, P.A.D., Rangel-Negrín, A. (2015). Diets of Howler Monkeys. In: Kowalewski, M., Garber, P., Cortés-Ortiz, L., Urbani, B., Youlatos, D. (eds) Howler Monkeys. Developments in Primatology: Progress and Prospects. Springer, New York, NY. https://doi.org/10.1007/978-1-4939-1960-4_2

[3]Fiorenza, L., & Bruner, E. (2018). Cranial shape variation in adult howler monkeys (Alouatta seniculus). American Journal of Primatology, 80(1), e22729. https://doi.org/10.1002/ajp.22729

[4]Van Belle, S. & Estrada, A. (2019). The Influence of Loud Calls on Intergroup Spacing Mechanism in Black Howler Monkeys (Alouatta pigra). International Journal of Primatology, 41(22), 265–286. https://doi.org/10.1007/s10764-019-00121-x

[5] Dunn,J., Halenar,L., Davies, T., Cristobal-Azkarate, J., Reby, D., Sykes, D., Dengg, S., Fitch, T., Knapp,L. (2015). Evolutionary Trade-Off between Vocal Tract and Testes Dimensions in Howler Monkeys, Current Biology,25(21) P:2839-2844. https://doi.org/10.1016/j.cub.2015.09.029. https://www.sciencedirect.com/science/article/pii/S0960982215011094.

[6]Kowalewski, M. M., Garber, P. A., Cortés-Ortiz, L., Urbani, B., & Youlatos, D. (Eds.). (2014). Howler monkeys: behavior, ecology, and conservation. Springer.

[7 ]Brividoro, M.V., Kowalewski, M.M., Scarry, C.J. et al. Patterns of Sleeping Site and Sleeping Tree Selection by Black-and-Gold Howler Monkeys (Alouatta caraya) in Northern Argentina. Int J Primatol 40, 374–392 (2019). https://doi.org/10.1007/s10764-019-00094-x