How to determine the winner in a battle for territory? Howler monkeys: Who roars louder?

As we all know, the lion's voice is earth-shaking and very penetrating, often scaring other animals. People usually use "lion's roar" to describe its roar.

The "Lion's Roar" skill derived from this is known as the secret skill of Shaolin Temple. When a master performs it, the enemy is often terrified and their hair stands on end. This skill has also become a superior martial art that martial arts masters compete to practice in martial arts novels or film and television dramas.

In fact, there are several animals whose roars are louder than the "lion's roar". In a popular online article published some time ago, "A List of the 10 Loudest Animals in Nature", the lion's roar is between 110-114 decibels, ranking tenth. Among the animals ranked ahead of it, there is a monkey whose roar is as high as 128 decibels and can be heard up to 5 kilometers away. It is a true howler monkey .

Howler monkeys roaring collectively. Image source: Artemii Sanin shutterstock

01

Hanging monkeys living in trees

Howler monkeys belong to the genus Howler of the family Therizinidae in the order Primates. They mainly live in the tropical rain forests of America. They have a sturdy body, and adult monkeys weigh more than 7 kilograms. They are the largest American monkeys.

One of the characteristics of howler monkeys is that their tails are long and can be used to wrap around them, so they were once included in the family of capuchins and were also called hanging monkeys. The tail of an adult howler monkey is between 70 and 90 centimeters long, which is about the same length as the body. The main functions of the monkey's tail are twofold: one is to hang itself upside down and eat leaves, fruits or flowers directly with its mouth; the other is to use the tail to hook food in front of the body and put it into its mouth. The tail does the work of the forelimbs, which can be used to climb or hold branches.

As the largest monkey in the world, howler monkeys are experts at jumping between trees because of their powerful forelimbs. They like to stay in trees for a long time, and even female monkeys raise and breastfeed their babies in trees. When a baby accidentally falls to the ground, the male monkey will yell at the female monkey until she gets down and takes the baby back to the tree.

From this we know that in a howler monkey family, the male monkey bears the responsibility of protecting the family, and also has the right to dominate other members. He is the "parent" who has the final say.

In fact, the male monkey parent has a cold-blooded side. He will strictly control the number of members in his family. Once the number exceeds the limit, he will expel the oldest children from the family. If the children are just cubs, he will wait until the cubs are mature before expelling them, but he will not care whether the other party can form a new family.

Howler monkeys in the jungles of South America Source: Wikipedia

02

The "gentleman" with a loud roar

In the forests of Costa Rica in North America, people often see groups of howler monkeys moving around by entwining their tails or grasping branches with their forelimbs. They often sit on trees to eat leaves, fruits or flowers, and make loud roars from time to time.

As the name suggests, the most prominent feature of howler monkeys is that their calls are loud and can travel far. They have thick necks, large mouths and jaws, and a peculiar hyoid bone in their throats (actually a box-like resonator). After howler monkeys contract their chests to push out air, the airflow passes through a hole on the hyoid bone to the huge "subwoofer" in the mouth, thus forming a huge and deep roar.

At first the roar was intermittent, then it became like a series of thunder, and then the resonance of the trees in the forest spread the sound several kilometers away.

Howler monkey's high pitched voice Source: Artemii Sanin shutterstock

Although roaring is physically demanding, howler monkeys, especially male monkeys, still roar several times a day. In addition to the aforementioned situation where the male monkey roars to direct the female monkey to get down and pick up the baby when it falls to the ground, howler monkeys also maintain some fixed roaring habits. For example, adult male monkeys like to make continuous roars in the early morning, one is to clear their mouths and throats, and the other is to warn other tribes not to approach their territory.

Fighting for territory is also the main platform for the "Monkey Roar" skill. Howler monkeys are typical social animals. When one monkey group enters the territory of another monkey group, the latter will take the initiative to launch a demonstrative roar. The battle between the two teams is like this: the monkeys automatically stand in two teams, the male monkeys stand in front of the team and roar, and the female monkeys and young monkeys cheer behind.

The battle is decided by the volume and duration of the male monkey's roar. The one with the greater momentum wins and occupies the territory, and the other monkey group leaves on its own initiative. Regardless of the outcome, the two sides will never engage in physical conflict. This "gentlemanly" style of using words instead of fists is extremely rare in the animal world.

It is worth mentioning that among the primates that like to roar, in addition to howler monkeys, there is also the famous gibbon. Gibbons start to cry at dawn, and the elders can last for several hours to inform other gibbons of their location and tell them not to invade. This is the scientific principle behind the poem "The monkeys on both sides of the river keep crying, and the light boat has passed through thousands of mountains" (Li Bai's "Early Departure from Baidi City").

Howler monkey jumping Photo credit: Artemii Sanin shutterstock

03

Eat more lazy vegetarians

Howler monkeys rarely move except for howling. They spend more than half of their daytime time lying or sleeping on tree branches. They are well-known for being lazy among their kind. Some scientists even call them "lazy howler monkeys."

The main reason for the reluctance to move is related to the survival mode and feeding characteristics of howler monkeys. Howler monkeys are typical herbivores that like to eat leaves, fruits and flowers. They do not have strong attack and defense capabilities, so they can only protect themselves by living in trees as much as possible.

In addition, it has two outstanding eating characteristics: one is that it eats very slowly, it can be said that it chews its food carefully. For it, nothing seems to be more important than roaring and eating; the other is that it has a large appetite, and the amount of food it eats every day can reach half of its own weight.

Howler monkeys eat slowly and eat a lot, which is directly related to the geographical environment. Although the tropical rain forests are full of evergreen trees and leaves are very abundant, they do not like the leaves that make up the vast majority of the food of tropical rain forest green plants. This is because these leaves are low in nutrients and high in cellulose, and howler monkeys do not have the enzymes to digest cellulose in their stomachs.

In other words, most of the leaves in the rainforest cannot be digested by howler monkeys. Even young leaves rich in protein are only selectively eaten by howler monkeys because of their low sugar content.

Howler monkey eating leaves Source: Wikipedia

In order to meet the energy needs of daily activities such as howling, the clever howler monkeys choose to eat slowly and eat more, and on the other hand, they achieve this through lying down and sleeping, and through gender division of labor. The gender division of labor is as follows: male monkeys are responsible for protecting the monkey group and commanding and coordinating family affairs; female monkeys are responsible for giving birth, caring for offspring, and temporary affairs arranged by male monkeys.

Haha, this is so similar to the family division of labor among ancient humans, no wonder they are primates!

【References】

1. "The Loud Voice in the Rainforest - Howler Monkeys", Youth Science and Technology, June 2009

2. "Male Howler Monkeys' "Beat the Fish and Bear's Paw"", Xu Jingxuan, VIP Journal Professional Edition

3. “Talking about Monkeys in the Year of the Monkey”, Qiao Yilun, Life World, April 2016

4. "A Brief Discussion on the Movement Methods of Primates", Yang Dong, Forestry Survey and Planning, No. 1, 2008

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