Everything about Sloth totally explained
The living
sloths comprise 6
species of medium-sized
mammals that live in
Central and
South America belonging to the
families Megalonychidae and
Bradypodidae, part of the
order Pilosa. Most scientists call the sloth
suborder Folivora, while some call it
Phyllophaga. Both names mean "leaf-eaters"; the first is derived from
Latin, the second from
ancient Greek.
This article mainly deals with the living tree-dwelling sloths. Until geologically recent times, large
ground sloths such as
Megatherium lived in
South America and parts of
North America, but along with many other animals they disappeared immediately after the arrival of humans on the continent. Much evidence suggests that human hunting contributed to the extinction of the American
megafauna, like that of far northern
Asia,
Australia,
New Zealand, and
Madagascar. Simultaneous climate change that came with the end of the last
Ice age may have also played a role in some cases. However, the fact that
ground sloths survived on the
Antilles long after they'd died out on the mainland points towards human activities as the agency of extinction.
Ecology
The living sloths are
omnivores. They may eat
insects, small
lizards, and
carrion, but their diet consists mostly of buds, tender shoots, and leaves, mainly of
Cecropia trees. They have made extraordinary adaptations to an
arboreal browsing lifestyle. Leaves, their main food source, provide very little energy or nutrition and don't digest easily: sloths have very large, specialized, slow-acting
stomachs with multiple compartments in which
symbiotic bacteria break down the tough leaves. 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.
Even so, leaves provide little energy, and sloths deal with this by a range of economy measures: they've 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 or 86 to 93 degrees Fahrenheit), and still lower temperatures when resting.
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
biomass in some areas. Of the six living
species, only one, the
Maned Three-toed Sloth (
Bradypus torquatus), has a classification of "endangered" at present. The ongoing destruction of South America's forests, however, may soon prove a threat to other sloth species.
Physiology
Sloth fur exhibits specialized functions: the outer hairs grow in a direction opposite from that of other mammals. In most mammals, hairs grow toward the extremities, but because sloths spend so much time with their legs above their bodies, their hairs grow away from the extremities in order to provide protection from the elements while the sloth hangs upside down. In moist conditions, the fur hosts two species of
symbiotic cyanobacteria, which may provide camouflage. The outer fur coat is usually a thick brown, but occasionally wild sloths appear to have a green tinge to their fur because of the presence of these bacteria. The bacteria provide nutrients to the sloth when licked during grooming. Sloths have short, flat heads; big eyes; a short snout; long legs; and tiny ears. They also have stubby tails, usually 6-7cm long. Altogether, sloths' bodies usually are anywhere between 50 and 60 cm long.
Sloths' claws serve as their only natural defense. A cornered sloth may swipe at its attackers in an effort to scare them away or wound them. Despite sloths' apparent defenselessness, predators don't pose special problems: sloths
blend in with the trees and, moving only slowly, don't 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. The majority of sloth deaths in Costa Rica are due to contact with
electrical line and
poachers. Despite their adaptation to living in trees, sloths make competent swimmers. Their claws also provide a further unexpected deterrent to human hunters - when hanging upside-down in a tree they're held in place by the claws themselves and often don't fall down even if shot from below.
Sloths move only when necessary and even then very slowly: they've about half as much muscle tissue as other animals of similar weight. They can move at a marginally higher speed if they're in immediate danger from a predator (4.5 m / 15 feet per minute), but they burn large amounts of energy doing so. Their specialized 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 sometimes remain hanging from branches after death. On the ground their maximum speed is 1.5 m (5 feet) per minute. They mostly move at 15-30 cm (0.5-1 feet) per minute.
It had been thought that sloths were among the most
somnolent animals, sleeping from 15 to 18 hours each day. Recently, however, Dr. Neil Rattenborg and his colleagues from the Max Planck Institute for Ornithology in Starnberg, Germany, published a study testing sloth sleep-patterns in the wild; this is the first study of its kind. The study indicated that sloths sleep just under 10 hours a day. They are particularly partial to nesting in the crowns of palm trees where they can camouflage as coconuts. They come to the ground to urinate and defecate only about once a week. They come to the same spot to do and are vulnerable while doing so. The reason for this risky behaviour is unknown.
Infant sloths normally cling to their mother's fur, but occasionally fall off. Sloths are very sturdily built and rarely die from a fall. In some cases they die from a fall indirectly because the mothers prove unwilling to leave the safety of the trees to retrieve the young. Females normally bear one baby every year, but sometimes sloths' low level of movement actually keeps females from finding males for longer than one year.
Classification
The living sloths belong to one of two families, known as the
Megalonychidae ("two-toed" sloths) and the
Bradypodidae (three-toed sloths). All living sloths have in fact three
toes; the "two-toed" sloths, however, have only two
fingers. Two-toed sloths are generally faster moving than three-toed sloths. Both types tend to occupy the same forests: in most areas, one species of three-toed sloth and one species of the larger two-toed type will jointly predominate.
However, their
adaptations belie the actual relationships of the living sloth
genera, which are more distant from each other than their outward similarity suggests. The two-toed sloths of today are far more closely related to one particular group of ground sloths than to the living three-toed sloths. Whether these ground-dwelling Megalonychidae were descended from tree-climbing ancestors or whether the two-toed sloths are really miniature ground sloths converted (or reverted) to arboreal life can't presently be determined to satisfaction. The latter possibility seems slightly more likely, given the fact that the small ground sloths
Acratocnus and
Synocnus which were also able to climb are among the closer relatives of the two-toed sloths, and that these together were related to the huge ground sloths
Megalonyx and
Megalocnus.
The
evolutionary history of the three-toed sloths isn't at all well-known. No particularly close relatives, ground-dwelling or not, have yet been identified.
It remains to be said that the ground sloths don't constitute a
monophyletic group. Rather, they make up a number of lineages, and as far as is known until the
Holocene most sloths were in fact ground-dwellers. The famous
Megatherium for example belonged to a lineage of ground sloths that wasn't very close to the living sloths and their ground-living relatives like the small
Synocnus or the massive
Megalonyx. Meanwhile,
Mylodon, among the last ground sloths to disappear, was only most distantly related to either of these.
- ORDER PILOSA
[
]- Suborder Folivora
- Family Bradypodidae
- Genus Bradypus (Three-toed sloths)
- Family Megalonychidae
Gallery
Image:MC Drei-Finger-Faultier.jpg|Brown-throated Three-toed Sloth (Bradypus variegatus), Cahuita National Park, Costa Rica.
Image:Zoo Dortmund Faultier.jpg|Choloepus sp., Dortmund Zoo.
Image:Megatherium americanum Skeleton NHM.JPG|Megatherium fossil.
Image:Scelidotherium leptocephalum side.jpg|Scelidotherium leptocephalum fossil. Muséum national d'histoire naturelle, Paris.
Image:Paramylodon harlani.jpg|Paramylodon harlani fossil, National Museum of Natural History, Washington, D.C.
Further Information
Get more info on 'Sloth'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://sloth.totallyexplained.com">Sloth Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
