The mantled howler monkey

The mantled howler monkey

The mantle howler monkey is one of the largest monkeys in Central America, with males reaching a height of nearly a meter and a weight of up to 10 kg. It is one of 15 species of howler monkeys. Unfortunately, some of those species are endangered, mainly because of habitat loss and capture, for instance for sale to serve as pets. They get their English name “mantled howler monkeys” from the long hairs on their sides, which resemble a mantle. They can use their tail they as an extra limb to keep their balance. The tail also has a bare tip so they have a better grip around branches. With it, they can hold their entire weight and even feel with it as with their hands. The tail can be up to 5 times longer than the rest of their body. Especially young monkeys can be seen regularly hanging on to their tails, older monkeys use the tail more as a stabilizer.


In the wild, howler monkeys live to be 15 to 20 years old. The monkey’s diet consists mainly of leaves, which of course is not the best source of energy. Therefore, the monkey also spends large parts of the day while resting. Moreover, they should not eat too much from the same tree, as some leaves are slightly poisonous. So they are changing trees regularly. In addition to leaves, they also eat fruits, nuts and flowers. The monkeys’ sense of smell is very well developed, so well in fact that they can smell ripe fruit from 2km away. This is partly due to their round, wide-open nostrils. They rarely drink, as they get most of their moisture from food. Only when it is very dry they occasionally descend from their tree to search for water.


Why the roar?

Their roar is an energy-saving way to communicate with other monkeys in the troop, as well as with competitors. In the morning and evening, they roar to mark their territory, and their roar is answered by other groups nearby. And although howler monkeys are strictly vegetarian, and generally not known to be aggressive, that roar can scare people quite a bit. Not surprising when you know that the sound can be heard up to 5 kilometers away. To roar so loudly, the monkeys have a hollowed-out hyoid bone near their vocal cords. A bone that all monkeys have, but that in howler monkeys is enlarged several times. It is mainly the males that you hear; the females also vocalize but are not as loud.

Troop animals

By the way, such a troop of howler monkeys can have up to 40 members, although about 15 is more average. The monkeys in a troop are usually not related to each other, because as soon as they reach sexual maturity they are expelled from the troop. The troop has a dominant male and several females with whom it mates. Despite not having a set mating season, most births are in the second half of December and in January. Pregnancy lasts six months, after which the baby remains close to mom for about 4 months. From about 10 weeks of age, the young begin to search for food on their own.

A riddle for science

By the way, did you know that there had been almost no apes in South America? All the native ape species of the Americas died out in the Eocene, some 35 million years ago. The ancestors of today’s New World came from North Africa. And given the distance and lack of fossils, it is unlikely that they made that trip by land, so now the hypothesis is that they crossed the ocean. Notswimming, of course, but clinging to driftwood, or on islands of torn-off pieces of land. At that time the sea level was even lower, so the journey would have taken “only” about 10-13 days. Too crazy to be true? Only future discoveries and science will be able to tell!

Foundation Adopt Rainforest has been working for more than 10 years to protect the habitat of these special howler monkeys. Would you also like to contribute to this effort? You can easily do so by adopting a piece of rainforest for these wonderful animals. You can do this for as little as €2.50 for a square meter. Adopt here

The biggest rainforests of the world

The world’s largest rainforests

It’s World Rainforest Day today (June 22)! A day to put our world’s rainforests in the spotlight because it’s mega important to protect them. Do you know which are the largest rainforests in the world? In this blog we will show them to you. We start at spot 10. (more…)

Strawberry poison dart frog

By Zoë Schreurs

In Costa Rica, you can’t ignore them: the Oophaga pumilio. Pumilio means dwarf, and although they are barely 3 cm tall, it is hard to miss the poisonous strawberry frogs. In English, they are called Strawberry Poison Dart frogs because indigenous peoples used to use their poison to makepoison darts. They are also affectionately called the “blue jeans frog,” because they often look like red frogs in jeans. Although they are by no means all the same colors. There are some that are completely red or blue, rather yellow, green or orange, or with black stripes or dots. In total, there are some 15 to 30 color variations.


Butterflies in Costa Rica

When a butterfly flies by, most people do stop for a moment to follow it with their eyes. They often have beautiful colors and the large soft wings compared to the small body make them look almost cuddly. In Costa Rica there are more than 1200 species of butterflies and of course we are very curious about the species that occur in the reservation of Adopt Rainforest.


Adopt Rainforest deploys park rangers to protect rainforest

In recent years, the reserve of the Adopt Rainforest Foundation has been easy for project manager Maarten to oversee. Two or three times a week he and the students make his rounds through the project area for the biodiversity research. For this research they visit several plots of the area, giving them a good insight into what is happening. Should any illegal logging occur, it is immediately noticed. The same goes for illegal hunting. In addition to the local presence, camera traps are hung at various places in the reserve. These are checked weekly. Should hunters or poachers walk through our reserve, this is quickly noticed.


High time for biodiversity!

High time for biodiversity

Did you know that 5% of all species of flora and fauna in the world live and grow in Costa Rica? Also, Costa Rica is in the global top 20 countries with the greatest biodiversity! Are you a real nature lover? Then put Costa Rica on your bucket list. But… before you pull your backpack and passport out of the  closet, we want to give you a lesson about biodiversity. Maybe you have what it is, but to refresh your memory we’ll explain it to you in this blog. (more…)

What does deforestation mean for our nature?

What is deforestation anyway? This term is used to describe the process by which trees give way to agriculture and livestock. Deforestation takes place in large numbers every day, especially in the Amazon rainforest. Not a pretty thing! The consequences? Cutting down trees not only means loss of our beautiful nature and biodiversity. It has an effect on the ambient temperature: it rises. This increase is caused by burning trees and because oxygen (O2) gives way to carbon dioxide (CO2) emissions. Trees store a lot of CO2 and this is released during deforestation. The numbers? Don’t be alarmed: around 13 million hectares of forest disappear on Earth every year, according to the FAO. To make it a little more tangible: this equals 18,207,280 football fields. Approximately 34 soccer fields per second! (more…)

Morpho butterfly in Costa Rica

This beautiful blue butterfly, measuring up to 15-20 cm, seems to appear and disappear with every flick of its wings. In fact, its underside is a clever trick of Mother Nature. On the underside, it is inconspicuous reddish-brown, with eyes to deter attackers. The bright iridescent blue, in turn, is to deter competition and attract females.


The most special sighting in our reservation so far!

In recent years we have already seen many rare and unusual animals in our reserve such as the Northern Nacked-tailed Armadillo, Black-and-White Hawk-Eagle and several felines. However, what we recently encountered is many times more interesting to scientists. In 1989, Epigomphus houghtoni, the Limon Knobtail, a dragonfly species was described by Stephen Brooks based on […]

Leaf-cutter Ants

Anyone who has traveled through the Americas knows them anyway, a stream of ants all carrying leaves with them. It looks like a mini highway that can go on for 30 meters. We’re talking about leaf-cutter ants of course. For tourists a source of amazement, for local farmers and vegetable gardeners a real plague that […]

The three-fingered sloth: the facts you didn’t know about this impressive mammal

What’s with the fur? Why do sloths sleep so much? This month, the three-fingered sloth is the animal of the month at Adopt Rainforest. And what’s more fun than hearing from one of the founders of Adopt Rainforest some fun facts that you won’t find in a standard biology book. Maarten van der Beek is one of the biologists at Adopt Rainforest and lives on the Work With Nature reserve in Costa Rica. (more…)

Bird Watching in Costa Rica

Costa Rica, a country of which almost half is rainforest, is a true birding paradise. More than 900 species of birds can be found here. One of the most beautiful and special birds that has its habitat in Costa Rica, however, is the Resplendent Quetzal. A good reason to go bird watching in Costa Rica!


Zoë on her wonderful experiences as a volunteer in Costa Rica

And then there you are, atop a hilltop, having a good cry. Or frantically trying not to let your fellow volunteer see how touched you are. My name is Zoë, I live near Hasselt in Belgium. I am an adult education teacher, and enthusiastic but very novice when it comes to nature. I would like to tell you about my wonderful experiences as a volunteer in the reserve of Adopt Rainforest.


International Census of the Great Green Macaw

Critically endangered parrot species Yesterday the research program of Adopt Rainforest participated in the Censo Internacional de la Guacamaya Verde 2022. Or in English the International Sensus of the Great Green Macaw. Throughout its distribution, dozens of organisations participate in the next days to get an understanding of the current state of this parrot species. […]