“Sloths” are given the dishonorable name of “sloth”.
But don’t you sometimes envy them and think (I wish I could live like this…)?
Sloths are the slowest mammals in the world. Their appearance of hanging leisurely from trees is so adorable that it makes you smile involuntarily.
Sloths spend most of their day sleeping, and even when they are awake, they stay still without moving. But that’s not because they are “lazy”. There is a deep reason for that. Well, what is that reason?

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Basic information about sloths.

Mammalia Xenarthra Pilosa Folivora.
There are two families and six species of sloths, and some extinct families. Sloths have long limbs (forelegs and hindlegs), and their whole body is covered with brownish-gray fur. They spend most of their lives on trees, and they eat, sleep, mate and give birth on trees.

【Megalonychidae.】
There are two species of “Linnaeus’s two-toed sloth” and “Hoffmann’s two-toed sloth”.
Length : about 60-70cm. Weight : about 8kg.
They look almost the same. They have two toes on their forelegs and three toes on their hindlegs.
They have no tail or only a slight trace of it.

＜Linnaeus’s two-toed sloth.＞
They have seven cervical vertebrae. All of the ones kept in Japan are “Linnaeus’s two-toed sloth”.

＜Hoffmann’s two-toed sloth.＞
They have one less cervical vertebra than Linnaeus’s two-toed sloth, with six.

【Bradypodidae.】
There are four species of “Brown-throated sloth”, “Pale-throated sloth”, “Maned sloth” and “Pygmy 　　three-toed sloth”.
Length : about 50cm-60cm. Weight : about 4kg-5㎏.
Long tail : 3-7cm.　

＜Brown-throated sloth.＞
They have brown throat.
Their eye rings are slightly longer than those of Pale-throated sloth.

＜Pale-throated sloth.＞
They have white throat.

＜Maned sloth.＞
They are smaller than other Bradypodidae.
Length : about 40-50cm. Weight : about 4kg.
They have long hair from the neck to the shoulder, forming a black mane.

＜Pygmy three-toed sloth.＞

They cannot live outside of mangrove forests.
They are endangered species, reduced to an estimated 200 individuals by hunting and mangrove logging.

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Q,Where do sloths live?

Sloths live on trees that are 10 to 30 meters high in the forest areas of Central and South America.

【Megalonychidae】
・Linnaeus’s two-toed sloth lives in the dense forests of northern Colombia and Venezuela, Suriname and northern Brazil, and northern Peru.
・Hoffmann’s two-toed sloth lives in the forests of Central America from Honduras to Brazil.

【Bradypodidae】
・Pale-throated sloth lives in Brazil.
・Brown-throated sloth lives in Brazil, Argentina, and Bolivia.
・Maned sloth lives in southern Brazil.
・Pygmy three-toed sloth lives on an island off the coast of Central and South America Panama.

Ｑ, Where does the sloth get its name?

They are called “sloth” in English, but in Japanese they are called “namakemono”. This time, I will introduce why they are called “namakemono” in Japanese and the origin of the name.

They were named “namakemono” from their appearance of hanging on trees and not moving. The scientific name “Folivora” means “one who eats leaves”, and the English name “Sloth” also means “laziness or slothfulness”.

Q, Why do sloths have long legs and claws?

Sloths have long limbs. Their forelimbs are longer than their hindlimbs, which makes them suitable for living on trees, clinging to trunks or hanging from branches. Moreover, sloths have hook-shaped claws that they use to hang from trees.

Q, Sloths don’t get tired of hanging on trees all the time?

Yes. Sloths’ organs such as liver, stomach, and kidneys are fixed to their ribs, so they do not compress their diaphragm when they are upside down, and they can stay upside down for a long time. Sloths hang from trees with their hook-shaped claws, but they do not fall from trees when they sleep because their fingers close. Sloths can hang from trees so firmly that they remain attached to the branches even after they die.

Q, Why don’t sloths move all the time?

Sloths sleep for about 15 to 20 hours a day. Sloths sleep either by curling up and sticking to a branch with their head between their forelimbs, or by hanging from a tree and curling up. In this state, sloths look like part of the tree from a distance, and they also camouflage themselves from carnivores. Also, when they are awake, they hardly move and just eat the leaves near them. They are so still that algae grow on their long fur.

But they are not just lazy and sluggish. In fact, a big reason for sloths’ “sluggish life” is “energy saving”. They live in a way that uses as little energy as possible, so that they can survive even if they eat very little and get very little nutrition.

Q, What do sloths eat?

Sloths’ food is leaves and algae that grow on their bodies. Two-toed sloths eat various kinds of leaves, buds, fruits, etc., while three-toed sloths eat only the leaves of the Cecropia genus. But leaves are low in calories and nutrients, and they cannot get enough nutrition to sustain their lives by eating them normally.

Another animal that eats leaves is the giraffe, but the giraffe sleeps only about 20 minutes a day, and spends most of the rest of the time eating leaves. This is because they have to eat a lot to get the nutrition they need to live.

Sloths are animals that eat the same leaves as giraffes, but they chose the opposite strategy to live on leaves with low nutritional value. Instead of eating a lot of leaves because they have little nutrition, they evolved into bodies that can live on little nutrition.

Q, Do sloths never get off trees?

Sloths are on the trees when they sleep, when they eat, and when they give birth. They stay still on the trees because they can blend in with the surrounding trees and are less likely to be found by carnivores. But they only come down from the trees once every week or ten days to poop. Why do sloths risk their lives to come down to the ground?

Actually, there is a surprising reason for this. The reason is the symbiotic relationship between moths and sloths. Moths of the Cryptoses tribe of the Megalopygidae family lay their eggs on sloth’s feces, and the hatched larvae feed on the feces and grow. The larvae eventually become moths and enter the sloth’s fur. And when these moths live in the sloth’s fur, the amount of nitrogen attached to the fur increases, and a lot of algae grow in the fur. And sloths can eat these algae as food.

Ｑ，How can sloths survive with little nutrition?

Sloths can live on a low-nutrient diet because they conserve as much energy as possible and do not use it. They spend most of the day sleeping, and only move a little to eat leaves or poop occasionally, so they have little muscle and can live on very little nutrition.

Sloths are also poikilothermic animals, even though they are mammals, and their body temperature fluctuates between 25 and 35 degrees Celsius according to the outside temperature. This allows them to save energy by not sweating or shivering.

Q, Is it true that sloths can starve to death even though they are full?

Yes, it’s true. Sloths sometimes starve to death even though they are full! Huh? Why? They starve to death even though they are eating? It’s strange, isn’t it?

Actually, sloths have intestinal bacteria living in their stomachs, and these intestinal bacteria break down and digest the leaves they eat slowly. This “slowness” is also surprising, and according to one zoologist, it takes up to 30 days to digest one leaf. But when the temperature is low for a long time, the body temperature of the poikilothermic sloths drops, and the activity of the intestinal bacteria slows down, and they sometimes starve to death even though they have enough food in their stomachs.

Q, How fast can sloths run?

Sloths are trying to run desperately, but they only move at about 2 to 5 meters per minute. They live a super slow life. Two-toed sloths can move faster than three-toed sloths.

Q, Can sloths swim?

Two-toed sloths cannot swim because their faces do not come out of the water when they enter the water. Three-toed sloths are good at swimming and can move faster than on land. This is thought to be an adaptation to the environment near the Amazon where three-toed sloths live.

The Amazon has a dry season and a rainy season because of its tropical rainforest climate. During the rainy season, their habitat is often flooded, so they cannot survive unless they are good at swimming.

Sloths are said to walk at a speed of 120 meters per hour, but they can swim at more than twice or three times that speed.

Q, How do sloth babies grow up?

Sloths give birth to one baby after a gestation period of six months to a year. Sloth babies cling to their mothers all the time. The baby is held by the mother, drinks milk, is protected, and spends several months. Even when they grow a little and eat food, they are with their mothers. When the child becomes independent, the mother gives the child the tree she lived in and moves to another place.

Q, What are the natural enemies of sloths? What kind of animals are targeted?

Sloths’ natural enemies are cougars and jaguars on the ground, and carnivorous birds of prey such as harpy eagles on the trees. Even if sloths find an enemy, all they can do is stop moving and try to blend in with the trees.

Sloths have long claws, but they are not for fighting. Once they are found, they cannot win no matter how they resist. So what do they do when they are caught by an enemy? When they are in such a situation, sloths do not resist at all and relax their whole body. By doing so, the pain is slightly relieved, they say…

Q, What kind of sloth was the extinct sloth?

Some of the extinct sloths are Eremotherium, Glossotherium, Megatherium, and Mylodon, which lived in South America from about 2 million years ago to 10,000 years ago, and Mylodon, which lived in Patagonia.

Especially Megatherium was the largest sloth on the ground, with a body length of 6-8 meters and a weight of about 3 tons. Unlike the living sloths, they lived on the ground. They were herbivorous, but large in size. They stood up on two legs, pulled trees closer with their long hooked claws, and ate leaves. They had a huge body covered with thick fur, huge hooked claws, and thick skin like armor. They were invincible, but they are thought to have become extinct due to hunting by humans who invaded the South American continent.

After the giant sloths on the ground became extinct, sloths evolved to eliminate waste and live a weak but eco-friendly life. Sloths are slow and weak, but they have survived without becoming extinct. Doesn’t it make you feel that being strong is not the only winner?

Q, Can sloths be pets?

When keeping rare animals, you may need to follow the laws set by each country. This time, we will introduce whether you can keep sloths at home in Japan.

Sloths can be bought at pet shops that deal with rare animals.
However, not only are they expensive, but they are also very difficult to keep in a general household.

Three-toed sloths are prohibited from being imported by the Washington Convention, so the ones sold in Japan are two-toed sloths. Two-toed sloths are more temperamental than three-toed sloths and will defend themselves with their sharp hooked claws and teeth when they feel threatened. Also, sloths are very delicate and may suffer from great stress and damage if they are touched by humans on a daily basis. In addition, in order for sloths living in tropical rainforests to stay healthy, they must maintain an environment of 26-30°C and 80% humidity.

Sloths are very cute and soothing, but for sloths and other rare animals that are not domesticated, please think carefully about whether it is really happy for them to be kept outside of zoos that have a suitable breeding environment.

There are zoos all over the country where you can observe sloths closely, so please visit a zoo and meet sloths and learn a lot about them.

Q, Where can I meet sloths?

Sloths are mysterious and charming animals. Where can you go to meet them?
You can meet sloths at zoos and safari parks! As of February 2021, the zoos where you can see two-toed sloths are as follows.

【Hokkaido.】
North Safari Sapporo.
【Kanto region.】
Nasu Animal Kingdom Saitama Children’s Zoo.
Oshima ParkChiba City Zoological Park.
【Chubu region.】
Cactus Zoological Park Nihondaira Zoo.
Ishikawa Zoo Asuwayama Park Amusement Park-Zoo.
 Higashiyama Zoo.
【Kinki.】
Kyoto Zoo.
Oji Zoo Misaki Park.
Adventure World Kobe Animal Kingdom.
Himeji Central Park.
【Chugoku region.】
Akiyoshidai Safari Land.
Tokiwa Zoo.
【Shikoku region.】
Noichi Zoological Park.
Tokushima Zoo.
【Kyushu region.】
Omuta Zoo Hirakawa Zoological Park.
Nagasaki Bio Park.
Oita Marine Palace.
Neopark Okinawa.

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Bibliography.

wikipedia ナマケモノ
https://ja.wikipedia.org/wiki/ナマケモノ

wikipedia メガテリウム
https://ja.wikipedia.org/wiki/メガテリウム

Zoocan　いきもの図鑑
http://www.zoocan.jp/zukan/index.cgi?288

GIZMOOD
https://www.gizmodo.jp/2016/08/there-is-a-reasonable-explanation-for-why-this-sloth-won-t-move.html

動物完全大百科・キリン
https://animalbook.jp/animalia/giraffe/

ナショナルジオグラフィックNews
https://natgeo.nikkeibp.co.jp/atcl/news/18/030200096/?P=1
https://natgeo.nikkeibp.co.jp/nng/article/news/14/6714/
https://natgeo.nikkeibp.co.jp/atcl/news/16/051700170/
https://natgeo.nikkeibp.co.jp/atcl/news/19/020100076/

川口先生のペットコラム
https://www.asahi-kasei.co.jp/hebel/pet/kenkyu/blog/2009.01-06.shtml/

AFP BBニュース「ナマケモノの内臓、逆さにぶら下がるための構造持つ 研究」
https://www.afpbb.com/articles/-/3013373

アイキャッチ画像
https://unsplash.com/photos/GTXvpZ2eTdA