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International Sloth Day is observed on October 20 every year to honor the adorable slow-moving, tree-dwelling and leaf-eating mammal. But what else do you know about sloths, except that they are super slow and super cute?

Sloths have become quite popular recently, thanks to the blockbuster animation movie "Zootopia." /VCG Photo Sloths have become quite popular recently, thanks to the blockbuster animation movie "Zootopia." /VCG Photo

1. There are six species of sloth

Sloths are tropical mammals that mainly live in South and Central America. The six species are divided into two categories: two-toed sloth and three-toed sloth. All sloths have three toes on their rear legs, but two-toed sloths have two toes on their front legs. The popular character in the blockbuster animation movie "Zootopia," named Flash, is a brown-throated three-toed sloth.

Do you remember Flash the Sloth? /VCG Photo Do you remember Flash the Sloth? /VCG Photo

2. Sloths are kins of the anteaters

Though they do not look alike.

These two belong to the same order in taxonomy. /VCG Photo These two belong to the same order in taxonomy. /VCG Photo

3. Some really amazing sloths no longer exist

The giant ground sloth, as large as an elephant, once lived in glaciers and oceans on the planet. But the species became extinct some 10,000 years ago.

The sloths were once known as jungle monsters. /VCG Photo The sloths were once known as jungle monsters. /VCG Photo

4. They can fail an eye test

Due to poor eyesight and hearing, sloths mainly rely on their sense of smell and touch to forage. Sloths do have color vision, which is generally absent in mammals.

This is not an unusual posture for a sloth. /VCG Photo This is not an unusual posture for a sloth. /VCG Photo

5. How slow are they indeed?

They usually move at an average speed of four meters per minute on trees. This number can reach around 4.5 meters per minute if they are threatened by a predator. Sloths only move when it's necessary. They move even slower on the ground, with a speed of three meters per minute.

Super, super slow. /VCG Photo Super, super slow. /VCG Photo

6. Excellent swimmers

Surprisingly, sloths are excellent swimmers and can reach speeds of 13.5 meters per minute. They can even cross rivers and swim between islands. This is because sloths can reduce their already slow metabolism even further. They can slow their heart rate to one-third of its normal pace, and hold their breath underwater for up to 40 minutes.

A totally vulnerable prey on the ground. /VCG Photo A totally vulnerable prey on the ground. /VCG Photo

7. They do not sleep as much as you thought

Though they spend 90 percent of their time motionless, sloths do not sleep all the time. The brown-throated sloth only sleeps 9.6 hours a day on average, probably less than you do on weekends.

Sloths are not as lazy as you thought. /VCG Photo Sloths are not as lazy as you thought. /VCG Photo

8. They poop once a week

This is probably the most fatal activity for a sloth. Sloths have large, slow-acting stomachs. As much as two-thirds of a well-fed sloth's body weight consists of the contents of its stomach, and the digestive process can take a month or more to complete. In this sense, they do not have to excrete frequently. But when they do, they have to do it on the ground, which makes them easily fall prey to jaguars and eagles.

Now you know why sloths often appear green. /VCG Photo Now you know why sloths often appear green. /VCG Photo

9. So why don't they just do it on the tree?

Because sloths has a small world to protect in their fur. The sloth's shaggy coat is a small ecosystem hosting green algae, which helps the sloth camouflage itself in the trees. The algae also provides nutrients to sloth moths, some species of which exist solely on sloths. When the sloths descend, moths lay their eggs on their host's poop.

The female sloth is anything but a good mother. The female sloth is anything but a good mother.

10. Every baby sloth is a miracle

Because of their super slow motion, many female sloths do not meet a male for a whole year or longer. Also, many baby sloths die if they fall off the tree, because the females do not want to leave the safe haven to rescue their babies.