Choloepus is a genus of mammals within the family Megalonychidae consisting of two-toed sloths. There are only two species of Choloepus : Linnaeus's Two-toed Sloth (Choloepus didactylus) and Hoffmann's Two-toed Sloth (Choloepus hoffmanni). These two species are the only members of the family Megalonychidae.
Although similar to the somewhat smaller and generally slower moving three-toed sloths (Bradypus), there is not a close relationship between the two genera. Recent phylogenetic analyses support the morphological data from the 1970s and 1980s that the two genera are not closely related and that each adopted their arboreal lifestyles independently. It is unclear what, if any, ground-dwelling sloth taxa the three-toed sloths evolved from, but the two-toed sloths likely evolved from one of the Caribbean megalonychids. 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.
As the name implies, they have only two toes on their forefeet, although, like other sloths, they have three toes on the hindfeet. They are also larger than three-toed sloths, having a body length of between 58 and 70 centimetres, and weighing 4-8 kilograms. Other distinguishing features include a more prominent snout, longer fur, and the absence of a tail.
Two-toed sloths have a gestation period of between six months and a year, depending on the exact species. The mother gives birth to a single young, while hanging up-side down. The young are born with claws, and are weaned after about a month, although they will remain with the mother for several more months, and do not reach sexual maturity until the age of 3 years, in the case of females, or 4-5 years, in the case of males.
Two-toed sloths spend most of their life hanging from trees, and are generally nocturnal animals. They are somewhat more active than three-toed sloths. Their body temperature depends at least partially on the ambient temperature; they cannot shiver to keep warm, as other mammals do, because of their unusually low metabolic rates and reduced musculature. Two-toed sloths also differ from three-toed in their climbing behaviors, preferring to descend head first.
They eat primarily leaves, but also shoots, fruits, nuts, berries, bark, and occasionally small rodents. They have large stomachs, with multiple chambers, which help to ferment the large amount of plant matter that they eat. Food can take up to a month to digest due to their slow metabolism. Depending on when in the excretion cycle a sloth is weighed, urine and feces may account for up to 30 percent of the animals body weight, which averages about 6 kilograms (about 13 pounds). They have a reduced, ever growing dentition, with no incisors or true canines, and which overall lacks homology with the dental formula of other mammals. Their first tooth is very canine-like in shape and is referred to as a caniniform. It is separated from the other teeth, or molariforms, by a diastema. The dental formula of two-toed sloths is: (unau)
(1758): Systema naturae perregna tria naturae, secundum classes, ordines, genera, species cum characteribus, differentiis, syonymis, locis. Laurentii :) Salvi, 824pp.
National Geographic: Two-Toed Sloth Profile
Bristol Zoo: Two-toed sloth
National Zoo: Two-toed sloth
America Zoo: Two-toed sloth
Animal Diversity: Family Megalonychidae
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Two-toed sloth