The world’s slowest mammalsSloths are friendly, very slow mammals living exclusively in trees. Trees are their whole world, and almost all vital processes take place there. On the ground, they move clumsily, stumbling over uneven terrain. Unlike their ancestors, they cannot lift their bodies above the ground.
1.Sloths are the general name for two families of the Xenarthra: a three-toed Bradypodidae and a two-toed Megalonychidae.
Xenarthra is a group of placental mammals. The group, differing in form and lifestyle, includes armadillos, glyptodonts, pampatheres, anteaters, tree sloths, ground sloths, and aquatic sloths.
2.The Bradypodidae, also called three-toed sloths, are a monotypic family of terrestrial, arboreal mammals.
The only genus belonging to this family is the sloth (Bradypus), with the following species:
- dwarf sloth
- three-toed sloth
- fringe sloth
3.Sloths live in forests of Central America and northern regions of South America.
The oldest surviving traces of sloths date back to the Pleistocene. At the time, there lived the Megatherium – great beast – that reached the size of a contemporary elephant. Contrary to its modern relatives, Megatherium was one of the largest mammals ever to walk Earth, weighing about 5 tons. It usually moved on four legs, but it also had a bipedal posture, reaching a height of about 6 meters. Such a large size allowed it to feed at heights not reached by modern herbivores. However, they also feed on leaves of yucca, agave, and grass.
4.A distinctive feature of sloths is the presence of three long fingers and toes, armed with three powerful, hook-shaped claws, thanks to which they can hang from tree branches.
Their claws are about 6 centimeters long.
5.They are medium-sized animals with a cylindrical body, thick and strong limbs, and a small, round head.
The length of their bodies varies from 48,5 to 75,5 centimeters, the tail is vestigial (reduced in two-toed sloths). They weigh between 2,5 and 10 kilograms. Females are usually larger and heavier than males.
6.Their hind limbs are shorter, and the forelimbs longer and finished with three fingers.
Their fingers are joined closely together and covered with a common skin, which unable independent moves.
7.Sloth’s fur consists of short and woolly and long and bristly hair.
The coloring depends on the species, e.g., the maned sloth’s fur is light-brown, its hair on the neck is black and falls on the shoulders. Three-toed sloth has a grey fur, brown of the sides, and a lighter spot between the shoulder blades (speculum), and a darker pattern in the middle, which helps distinguish females from males. There is a secretory gland in this area, which probably bears high importance during mating.
8.The hair of the three-toed sloth grows in ventral to dorsal direction, undoubtedly due to the “hanging” lifestyle and the climate in which it lives.
Sloths develop bacteria and algae in their fur, which gives it its greenish color. The greenish color of the coat and the sloth’s slow habits provide them with effective camouflage in trees – hanging sloth body resembles a bundle of branches. There are no algae in the fur of sloths breed in captivity in zoos. Moreover, four species of beetles and nine species of moths live permanently in their fur.
9.Sloths have 18 continuously growing teeth: 10 in the jaw and 8 in the mandible.
Their structure is primitive, does not allow to distinguish molars and premolars. They lack incisors and canines.
10.Sloths are herbivores, and their diet consists of leaves, flowers, fruit, and shoots.
Their stomachs are multichambered and inhabited by cellulose-eating bacteria. Digestion is very slow. Sloths descend to the ground to defecate, but it happens only once a week.