Day 388#: Mantled Howler Monkey
Today's animal of the day is the Mantled Howler Monkey (Alouatta palliata)!
Photo credit: Dr. Ariel Roriguez-Vargas
This species of New World monkey inhabits the tropical rainforests of Central America, as well as a tiny sliver of South America and the southernmost tip of Mexico. They are called howler monkeys because males have an enlarged hyoid bone, which is a hollow horseshoe-shaped bone located near their vocal cords. This greatly increases the volume of their vocalizations, which they use to communicate with each other over long distances. The "mantled" part of their name comes from the long guard hairs on their sides, which are coarser than the rest of their coats and help to protect the softer fur underneath.
Photo credit: Manuel Raab
These monkeys tend to live in large groups that usually have somewhere between 10 and 20 members. However, they've occasionally been seen in groups as large as 40 individuals! Adults in these groups tend to be unrelated, since juveniles leave their families before reaching sexual maturity in order to avoid inbreeding, and are led by a dominant male. Mantled howler monkeys will form a territory that can range in size from 25 to 148 acres. Different groups will often have overlapping territories, but will try to avoid encountering each other while foraging. If two groups meet, they usually end up trying to bully each other into going away. However, unlike some other types of primates, they won't super aggressively patrol their borders and try to kill any and all intruders.
Photo credit: Arturo de Frias Marques
Their diet mostly consists of leaves, as well as occasionally fruit. However, leaves make up the majority of their diet. Unlike many other types of New World monkeys, mantled howlers have full three-color vision, which means that they can see all three primary colors and all their different combinations. Most New World monkeys only have two-color vision and thus can't see as many different colors as the mantled howlers can. This ability helps them to find younger leaves, which tend to be more reddish since the trees haven't pumped them full of chlorophyll yet. Younger leaves are easier to chew than older ones, and depending on the species, also tend to have less toxins in them. Because leaves don't provide the monkeys a lot of energy, they spend most of their time resting. They are most active during the day, but still only spend about 3/4ths of that time resting. Compared to many other primates, they spend surprisingly little time socializing with one another, with much of their time not resting being used to forage for food.
Photo credit: Manuel Raab
While the species as a whole is considered to be vulnerable by the IUCN, there are three distinct subspecies, all of which have different conservation statuses. The nominate subspecies is the golden-mantled howler (A. p. palliata), which can be commonly found throughout Central America and is considered to currently have a stable population. Meanwhile, the Ecuadorian mantled howler (A. p. aequatorialis) is considered to be vulnerable, and the Mexican howler (A. p. mexicana) is full-on endangered! Like many other rainforest animals, habitat loss is the biggest threat to this species' survival.
Photo credit: Andrés León-Reyes
As more and more forests are cut down, these monkeys not only have nowhere to live but are also running out of food. Not every type of leaf is edible to them, and malnutrition has caused some populations to experience an increase in illnesses and physical ailments, like rickets. These monkeys play an important role in the rainforest as seed dispersers, since when they do occasionally eat fruit, they transport the seeds away from the parent tree and then poop them out in a place where the seedling doesn't have to compete with its parent or siblings. There are even some species of plant that require their seeds to pass through an animal's digestive tract in order to germinate. In addition to this, there are certain types of dung beetles that rely on these monkeys as a food source, since they poop A LOT! Luckily, the sedentary lifestyle and small home ranges of this species seem to have helped it fare better than some other monkey species that need more room to roam. But we should still try to protect as much of the remaining rainforests as we can, not just for this species but for the countless other organisms that rely on them as well, which includes humans!
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