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| Sloths
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A sloth, as depicted in the 1851 Illustrated London Reading Book | ||||||||
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Megalonychidae Bradypodidae |
Sloths have made extraordinary adaptations to an arboreal browsing lifestyle. Leaves, their main food source, provide very little energy or nutrition and do not digest easily: sloths have very large, specialised, slow-acting stomachs with multiple compartments in which symbiotic bacteria break down the tough leaves. Sloths may also eat insects and small lizards and carrion. 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 as long as a month or more to complete. Even so, leaves provide little energy, and sloths deal with this by a range of economy measures: they have very low metabolic rates (less than half of that expected for a creature of their size), and maintain low body temperatures when active (30 to 34 degrees Celsius), and still lower temperatures when resting.
Sloths move only when necessary and then very slowly: they have about half as much muscle tissue as other animals of similar weight. Their specialised hands and feet have long, curved claws to allow them to hang upside-down from branches without effort; while they sometimes sit on top of branches, they usually eat, sleep and even give birth hanging from limbs. They come to the ground, to urinate and defecate, only about once a week.
Sloth fur too exhibits specialised functions: the outer hairs grow in the opposite direction to that of other mammals (so as to provide protection from the elements despite living legs-uppermost), and in moist conditions host two species of symbiotic blue-green algae, which provide camouflage and possibly extra nutrition, either licked directly from the fur or absorbed through the skin.
Despite sloths' apparent defencelessness, predators do not pose special problems: in the trees sloths have good camouflage and, moving only slowly, do not attract attention. Only during their infrequent visits to ground level do they become vulnerable. The main predators of sloths are the jaguar, the harpy eagle, and humans. Despite their adaptation to living in trees, sloths make competent swimmers.
Infant sloths normally cling to their mother's fur; those that fall off die in some cases, because the mothers sometimes prove unwilling to leave the safety of the tree to retrieve them.
Until geologically recent times, large ground-dwelling sloths of the Megatherium type lived in North America, but along with many other species they became extinct immediately after the arrival of humans on the continent. Much evidence suggests that the extinction of the American megafauna, like that of AustraliaAustralia is the sixth-largest country in the world (geographically), the only one to occupy an entire continent, and the largest in the region of Australasia. Australia includes the island of Tasmania, which is an Australian State. Its neighbouring count, far northern AsiaThe continent of Asia is defined by subtracting Europe and Africa from the great land mass of Africa-Eurasia. The boundaries are vague, especially between Asia and Europe: Asia and Africa meet somewhere near the Suez Canal. The boundary between Asia and E, and New ZealandFor alternative meanings, see New Zealand (disambiguation). New Zealand is a country formed of two major islands and a number of smaller islands in the southwestern Pacific Ocean. A common Mori name for New Zealand is Aotearoa popularly translated as Land, resulted from human activity. Nevertheless, debate on the matter continues.
The living sloths belong to one of two families, known as the two-toed and three-toed sloths. Both families have three toes: the "two-toed" sloths, however, have only two fingers. Two-toed sloths are generaly faster moving than three-toed sloths. Both types tend to occupy the same forests: in most areas, a particular single species of three-toed sloth and a single species of the larger two-toed type will jointly predominate.
Although unable to survive outside the tropical rainforests of South and Central America, within that environment sloths are outstandingly successful creatures: they can account for as much as half the total energy consumption and two-thirds of the total terrestrial mammalian biomassBiomass is the organic non- fossil material of biological origin, collectively. For example, plants (including trees) and animals are biomass, as are the materials they produce, such as animal droppings and wood. The most successful animal of the earth, i in some areas. Of the five species, only one, the Maned Three-toed Sloth, has a classification of "endangered" at present. The ongoing destruction of South America's forests, however, may soon prove a threat to the others.
The term sloth can also transfer metaphorically to other slow-moving animals, including the Sloth BearSloth Bear : Animalia : Chordata : Mammalia : Carnivora : Ursidae Melursus ursinus Binomial name Melursus ursinus ( Shaw, 1791) The Sloth Bear Melursus ursinus is a nocturnal bear with shaggy fur which inhabits the lowland forests of India, Nepal, Banglad of India, and several primates, including species of slow loris, lemur and galago. The Koala has been called the " Australian sloth".
All these animals receive their name from the noun sloth, which is simply the Middle English noun-form of the adjective slow (formed in the same way as true→truth). In modern usage, however, it means "lazy, inactive, idle, indolent, sluggish, and slow"; these qualities make Sloth one of the Seven deadly sins.
Xenarthrans