Native to the lowland tropical forests of South and Central America, sloths are tree-dwelling mammals known for their slow-moving ways. Their low metabolic rate allows them to spend 15 to 20 hours per day sleeping. They move through the forest canopy at a rate of about 40 yards per day, spending their waking hours resting, sunbathing, and feeding on leaves. They descend from the trees in six-day intervals to use the bathroom and occasionally drop into some water for a swim. In fact, the long-armed animals are known to be pretty terrific swimmers.
There are two different types of sloths: two-toed and three-toed. The two-toed sloths have the ability to climb and position themselves vertically but end up spending a majority of their time hanging horizontally, using their large extremities to move along branches and vines. The three-toed sloths move in a similar way, but you often see them sitting in the forks of trees rather than hanging from branches. There’s a total of six species altogether: Hoffman’s two-toed sloth, Linnaeus’s two-toed sloth, brown-throated sloth, pale-throated sloth, maned sloth (which is the most vulnerable), and pygmy three-toed sloth (which is critically endangered).
The sloths’ closest relatives are anteaters and armadillos. All of them belong to an ancient group of mammals called the xenarthra. This group can attribute their bizarre behavior and appearance to the fact they evolved in isolation around 80 million years ago, when South America was still an island. Once upon a time, this group of mammals even included a giant ground sloth, called megatherium, which was the size of an Asian elephant. This creature most likely became extinct following the last ice age.
Sloths have a four-part, multi-chambered stomach that slowly digests the tough and toxic leaves that make up their diet. That content consists of 30 percent of their body weight. Just like everything else in the sloth’s life, digestion is slow. It can actually take up to a month for a sloth to digest one meal. Since their diet isn’t very nutritious and it takes a long time to digest, it’s possible that this contributes to sloths’ lack of energy. The problem is that if they processed food any faster, sloths would actually poison themselves. So while they say that sloths spend 70 percent of their time resting, they’re not being lazy. They’re just working really hard to digest their food.
Sloths are also very sensitive to temperature change. They are heterothermic, so they don’t have great control over their body temperature. Their temperature can range from 25 to 35 degrees Celsius (which is 77 and 95 degrees Fahrenheit), and their body temperature can drop to as low as 20 degrees Celsius (68 degrees Fahrenheit), making them extremely lethargic. While they are sensitive in this area, their thick skin does allow them to withstand severe injuries.
Sloths do everything upside down—even mate. Courting starts with a female’s mating scream, which attracts the other males in the area and informs them that she’s ready to mate. Males will hang from branches by their feet and fight for the female by pawing at each other. A sloth can be pregnant anywhere from five to six months, but certain types of sloths can have gestation periods up to 12 months. Sloths only have one baby at a time, and after that baby is born, it rides around clinging to its mother’s belly for weeks. Even after they stop clinging to their mother, little sloths stay may stay by their mothers’ sides until at least five months of age. With some sloths, reproduction is seasonal, while others (such as the maned sloth) may breed throughout the year. Reproduction in pygmy three-toed sloths, however, has not yet been observed. These sloths are so hard to maintain in captivity that very little is actually known about their breeding habits or any other behaviors they may exhibit.
Along with being excellent swimmers, known for doing the breaststroke with ease, sloths maintain a low level of movement. Combined with the camouflage of the trees, this makes them difficult for predators to notice. They can climb only 6 to 8 feet per minute which makes perfect sense given that their scientific name, bradypus, is Greek for “slow feet.”
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