A three-toed sloth can rotate its head nearly 90 degrees or more, and its mouth is shaped in a way that makes the animal appear as if it's always smiling.
Credit: Bryson Voirin.
Sloths are tropical mammals that live in Central and South America. They use their long claws to hang onto branches while they feast on the leaves that other animals can't reach. Unfortunately for the sloth, their long claws — 3 to 4 inches (8 to 10 centimeters) — make walking on the ground difficult, so they spend most of their time in the tall trees they call home.
There are two categories of sloths. The two-toed sloth is slightly bigger than the three-toed sloth, though they share many of the same features. They are about the size of a medium-sized dog at around 23 to 27 inches (58 to 68 cm) and 17.5 to 18.75 pounds (about 8 kilograms).
Thousands of years ago, sloths were much bigger, according to the San Diego Zoo. Ancient sloths could grow to be as large as an elephant. They roamed North America and became extinct around 10,000 years ago.
Though their ancestors lived in North America, modern sloths live in Central and South America, enjoying the tall trees found in rain and cloud forests. Sloths prefer sleeping while curled into a ball in the fork of a tropical tree. They also like to sleep hanging by their claws from tree branches.
For the most part, a sloth's life revolves around sleeping and eating in their tree homes. The only times these mammals leave their tree is to use the bathroom and to take a swim.
Sloths in captivity sleep from 15 to 20 hours per day, which can leave them very little time for social activities. Sloths in the wild, though, sleep about as much as humans, according to research by the Planck Institute for Ornithology in Starnberg, Germany.
After around nine hours of sleep, the sloth still doesn't make an attempt at getting friendly with others. They live solo lives. The closest a sloth gets to social time is sleeping in the same tree with another sloth.
Sloths mate in trees and give birth to their young in trees. Courting starts when a female yells a mating scream to let the males in the area know she is ready to mate. Males will fight for her by hanging from branches by their feet and pawing at each other. The victor wins the prize of mating with the female.
Like many other mammals, sloths only have one baby at a time. Baby sloths have a gestation of five to six months for some types sloths and as much as 11.5 months for others, such as the Hoffman's two-toed sloth.
After they are born, the babies aren't in a hurry to leave their mother. They ride around clinging to their mother's belly for several weeks after birth. Even after they stop dangling from their mother, little sloths stay by their mother's side for up to four years.
The tough leaves in a sloth's diet are difficult to digest. Sloths have a four-part stomach that slowly digests the leaves with bacteria. It can take up to a month for a sloth to digest one meal. Their leafy diet isn't very nutritious though, so they don't get much energy from it. This may be why sloths are so slow.
The sloth's scientific name is Bradypus tridactylus. Here is its taxonomy according to the National History Museum:
- Empire: Eukaryota
- Kingdom: Animalia
- Phylum: Chordata
- Class: Mammalia
- Order: Pilosa
- Superfamily: Folivora
- Family: Bradypodidae
- Genus: Bradypus
- Species: Choloepus (lame foot), Choloepus didactylus (Linnaeus's two-toed sloth), Choloepus hoffmanni (Hoffmann's two-toed sloth), Bradypus variegatus (brown-throated sloth), Bradypus torquatus (the maned sloth), Bradypus tridactylus (the pale-throated sloth), Bradypus pygmaeus (pygmy three-toed sloth)
The pygmy three-toed slothis on the IUCN Species Survival Commission's top 100 listof most threatened species. These tiny sloths can only be found on Escudo Island, which is found off the coast of Panama.
Other facts about sloths
Its scientific name, Bradypus, is Greek for "slow feet," which makes sense since it is the world's slowest animal. It is so slow, in fact, that algae grows on its fur, according to National Geographic. The algae works to the sloth's advantage, though. The green of the algae helps the sloth blend into the trees, hiding it from predators.
Compared to most mammals, a sloth moves very slowly. Sloths can climb only 6 to 8 feet (1.8 to 2.4 meters) per minute.
Sloths are excellent swimmers. Like humans, they can do the breaststroke with ease. To get to the rivers for a swim, sloths will drop themselves off of branches into the water.
Since sloths bodies are only 25 percent muscle, they can't shiver when they are cold to warm up. It is a good thing they live in a tropical climate and are covered in fur. There are times of cold in the forest, though. If a female gets too cold, she is unable to digest food. If her young is still nursing, she may starve to death.
A sloth only has its claws for defense against predators. However, its very low level of movement and the camouflage make it difficult to notice.
Nina Sen contributed to this article.