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A sloth is an arboreal mammal indigenous to the South American Rainforests. The name has come to suggest laziness or slowness, and it is rooted in the easy, slow-moving lifestyle of this animal. It is very slow and deliberate in its movements, living upside down in rainforest trees for most of its life. The digestive system of this animal is also slow, and a traditional meal of leaves may take as much as a month to completely digest.
The modern sloth is relatively small in size, and most are approximately 2 feet (0.61 m) long. They may weigh around 9 pounds (roughly 4 kg). They have small eyes and ears, and only some varieties have tails. Their brown or grey coats are fuller toward the head and upper body, and they have an undercoat of dense fur. Average life expectancy in the wild ranges between 10 and 20 years, while an animal in captivity may live up to 40 years.
The prehistoric ancestor of this animal is the Giant Ground Sloth, Megatherium, which may have been as large as the modern elephant. Unlike modern sloths, it was not arboreal, and its size made it virtually invulnerable to predators. Past studies suggest the saber-toothed tiger might have preyed on this animal, but most scientists now dismiss this suggestion. It was simply too large and could counter an attack viciously if necessary.
Like its prehistoric ancestors, today’s sloths are mostly herbivores. They occasionally eat small insects and lizards, but in general, their digestive system is ideally suited to consuming leaves from rainforest trees. These animals seldom descend from their arboreal homes because they do not need to drink water; they get as much hydration as they need from leaf consumption.
The leaves sloths consume are not easy to digest, and do not provide much in the way of energy, leading to the animals' slow movement. Their stomachs have several compartments, loaded with tiny bacteria that help break down the cellulose of leaves, yet their metabolism remains sluggish. Most sleep up to two-thirds of the day and maintain a very low body temperature.
There are several species of sloth, which can be classed as either two-toed or three-toed, a somewhat misleading classification. Both classes have three toes on their back feet, but the two-toed varieties have two fingers on their front hands or paws. Three-toed animals are slightly larger than their two-toed cousins, but the two-toed varieties are a bit faster moving.
When cornered by a predator, such as the harpy eagle or the jaguar, a sloth can be quick, using its long claws to discourage attacks. It is often successful in defending itself, and most animal deaths are due not to predators, but to electrocution from contact with electric wires.
Though the rainforest is diminishing, only one species, the Maned Three-Toed Sloth, is considered endangered at this time. Further destruction of the rainforest will likely result in endangered classification for the other four species. These animals have adapted to human encroachment on their territory, however, and since they do not pose a threat to humans, they are usually left alone.