These primates are a fundamental part of the regeneration cycle of tropical forests, but they are in serious danger of extinction.
Howler monkeys arrived long before human populations in the habitats they now share. They eat the things we don’t, such as the leaves from trees.
Rural communities living near the monkeys say that these animals provide them with some services. For example, their howls announce the time of day and changes in the weather.
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However, the function of these animals goes much further. They are the great farmers of the forest: “those in charge of dispersing and germinating seeds,” says Dr. Juan Carlos Serio Silva, who heads the Group of Trans-disciplinary Studies in Primatology at the Institute of Ecology (INECOL).
In fact, their work is very important for the regeneration of forests, but they are in danger of extinction according to the International Union for Nature Conservation (IUCN) Red List.
In Mexico, there are three species of wild primates, howler monkeys or mantled howlers (brown and black) and spider monkeys, which are all endangered.
The threats that howler monkeys face are:
The IUCN has estimated that the population of these creatures will decline by up to 60% over the next 30 years.
Howler monkeys feed on the leaves and wild fruit of more than 150 species of trees. Their work as farmers actually consists of eating and defecating seeds. When the seeds reach the monkey’s digestive tract, their outer layer becomes thinner, and they are ready to germinate when expelled.
Everything the monkeys eat spends 21 hours in their stomachs, during which time the outer cuticles of the seeds are thinned.
“This process means there are greater possibilities of germinating in greater numbers and more quickly,” explains Juan Carlos Serio Silva, who has already published these findings on the specialized site Prima-T.
The process favors the prompt germination of seedlings, that is, the first stages of development of a plant, from the moment the seed germinates to when it acquires its first true leaves.
In addition to preparing the seeds, these primates also spread them through the forest. They do this thanks to their prehensile tail, which helps them move through the trees.
Howler monkeys carry out the primary dispersal, only defecating the seeds. These often fall in suitable places, but when they don’t, they are planted by other animals such as beetles.
“The beetles take the whole feces with the seeds and bury them, concluding the planting process,” explains Dr. Serio Silva.
He adds that his team has followed these insects to the place where they carry the balls of excrement. “The seedling is ready within weeks,” he says.
The primates’ diet includes the “ramon” or “breadnut,” wild figs, hog plums, mamey, and sapotes. They also eat trees such as Spanish cedar, swamp dogwood, and the fruit of Mexican palmettos.
The diet of these farmers includes 50 different types of fruit per day. “So, those little howler monkeys are responsible for you being able to eat your favorite fruit.”
The main threats to howler monkeys are the destruction of their habitat, their capture and sale as pets, and their use as a source of food for some local populations. (Photo: Jorge Ramos / INECOL)
The three species of monkeys that exist in Mexico are considered in danger of extinction according to Nom059, in effect since 2010, of the Secretariat of Environment and Natural Resources (SEMARNAT).
“There is no census or estimate of how many monkeys there are, but we do know that the habitat of these animals is decreasing,” warns the specialist Serio Silvia, who says he loves these animals.
When their habitat is disturbed, the quality and quantity of their diet is reduced, and therefore their work as farmers is threatened. Some groups of monkeys migrate or die because they have no resources and nowhere to sleep or eat, he explains.
Another problem faced by these species is that people sell them, even though this is prohibited in Mexico. The howler monkey is among the most illegally traded groups of animals in the country.
Illegal traffickers obtain young offspring by killing their mothers or entire groups. According to a study carried out by INECOL, only two or three out of every ten specimens captured reach the market.
“Mexican primates should also be a priority for conservation, not only because they’re related to us but also because they play a vital role in the regeneration of tropical forests. These animals are our natural heritage. They’re part of our identity from ancient times,” says the expert.
Juan Carlos Serio Silva and his trans-disciplinary team have been studying Mexican primates in their natural habitat for 30 years in several states of southeastern Mexico so as to develop an image, conservation, and action strategy involving academia, civil society, and government to promote their protection and the conservation of forests.
For example, they put on the Festival of Monkeys: Treasures of Los Tuxtlas, the International Week of the Black Mantled Howler Monkey, and the traveling festival Monkeys Come to Your Community. All three are held at strategic points in the country.
“These annual events elevate the profile and importance of monkeys in the places where they are from. They include artistic, educational, and environmental activities. They also provide a forum for groups of artisans from different communities of the region to display what they produce based on the image and importance of these primates.”