The Mantled howler (Alouatta palliata)

Jun 23, 2019 Interesting Creatures in Guyana, News

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The mantled howler (Alouatta palliata), or golden-mantled howling monkey, is a species of howler monkey, a type of New World monkey, from Central and South America. It is one of the monkey species most often seen and heard in the wild in Central America. It takes its “mantled” name from the long guard hairs on its sides.

The mantled howler is one of the largest Central American monkeys, and males can weigh up to 9.8 kg (22 lb). It is the only Central American monkey that eats large quantities of leaves; it has several adaptations to this folivorous diet. Since leaves are difficult to digest and provide less energy than most foods, the mantled howler spends the majority of each day resting and sleeping. The male mantled howler has an enlarged hyoid bone, a hollow bone near the vocal cords, which amplifies the calls made by the male, and is the reason for the name “howler”. Howling allows the monkeys to locate each other without expending energy on moving or risking physical confrontation.
The mantled howler lives in groups that can have over 40 members, although groups are usually smaller. Most mantled howlers of both sexes are evicted from the group they were born in upon reaching sexual maturity, resulting in most adult group members being unrelated. The most dominant male, the alpha male, gets preference for food and resting places, and mates with most of the receptive females. The mantled howler is important to the rainforest ecology as a seed disperser and germinator. Although it is affected by deforestation, it is able to adapt better than other species, due to its ability to feed on abundant leaves and its ability to live in a limited amount of space.
The mantled howler’s appearance is similar to other howler monkeys of the genus Alouatta except for coloration. The mantled howler is primarily black except for a fringe of yellow or golden brown guard hairs on the flanks of the body earning the common name “mantled” howler monkey. When the males reach maturity, the scrotum turns white.
Females are between 481 and 632 mm (18.9 and 24.9 in) in body length, excluding tail, and males are between 508 and 675 mm (20.0 and 26.6 in). The prehensile tail is between 545 and 655 mm (21.5 and 25.8 in) long. Adult females generally weigh between 3.1 and 7.6 kg (6.8 and 16.8 lb), while males typically weigh between 4.5 and 9.8 kg (9.9 and 21.6 lb). Average body weights can vary significantly between monkey populations in different locations. The brain of an adult mantled howler is about 55.1 g (1.94 oz), which is smaller than that of several smaller monkey species, such as the white-headed capuchin.
The mantled howler shares several adaptations with other species of howler monkey that allow it to pursue a folivorous diet, that is, a diet with a large component of leaves. Its molars have high shearing crests, to help it eat the leaves, and males have an enlarged hyoid bone near the vocal cords. This hyoid bone amplifies the male mantled howler’s calls, allowing it to locate other males without expending much energy.
The mantled howler is the most folivorous species of Central American monkey. Leaves make up between almost 50% and 75% of the mantled howler’s diet. The mantled howler is selective about the trees it eats from, and it prefers young leaves to mature leaves. This selectivity is likely to reduce the levels of toxins ingested, since certain leaves of various species contain toxins. Young leaves generally have less toxins as well as more nutrients than more mature leaves, and are also usually easier to digest. Mantled howler monkeys possess large salivary glands that help break down the leaf tannins by binding the polymers before the food bolus reaches the gut. Although leaves are abundant, they are a low energy food source. The fact that the mantled howler relies so heavily on a low energy food source drives much of its behaviour – for example, howling to locate other groups and spending a large portion of the day resting.
Fruit can also make up a large portion of the mantled howler’s diet. When available, the proportion of fruit in the diet can be as much as 50%, and can sometimes exceed the proportion of leaves. The leaves and fruit from Ficus trees tend to be the preferred source of the mantled howler. Flowers can also make up a significant portion of the diet and are eaten in particularly significant quantities during the dry season. The mantled howler tends to get the water it needs from its food, drinking from tree holes during the wet season, and by drinking water trapped in bromeliads.
Like other species of howler monkeys, almost all mantled howlers have full three colour vision. This is different from other types of New World monkeys, in which most individuals have two colour vision. The three colour vision exhibited by the mantled howler is believed to be related to its dietary preferences, allowing it to distinguish young leaves, which tend to be more reddish, from more mature leaves.
The mantled howler is regarded as “least concern” from a conservation standpoint by the IUCN. Nonetheless, its numbers may be adversely affected by rainforest fragmentation which has caused forced relocation of groups to less habitable regions.
However, the mantled howler can adapt to forest fragmentation better than other species due to its low energy lifestyle, small home ranges and ability to exploit widely available food sources. The mantled howler is important to its ecosystems for a number of reasons, but especially in its capacity as a seed disperser and germinator, since passing through the monkey’s digestive tract appears to aid the germination of certain seeds. Dung beetles, which are also seed dispersers as well as nutrient recyclers, also appear to be dependent on the presence of the mantled howler. The mantled howler is protected from international trade under Appendix I of the Convention on International Trade in Endangered Species (CITES). [Source: Wikipedia]

 

 

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