Sloths 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.
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.
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:
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.
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.
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.
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.
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.
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.
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.
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.
Their body temperature varies from 86 to 95 Fahrenheit.
Sloths do not regulate their body temperature like most mammals by changing their metabolic rate but moving from sunny areas to shade. It results in lower caloric requirements than in other mammals of similar size. That is the reason why plants are entirely sufficient for sloths.
Sloths move very slowly, with an average speed of 0,24 kilometers per hour.
They lead a sedentary life, traveling a distance of 24 meters a day – 17 meters during the day and 5 meters at night. Moving takes about 6-17% of the time during the day. Sloths spend 60-80% of the day resting, 7-17% for feeding, and 1-6% for courtship.
The animals mate at the end of the dry season, and at the beginning of a rainy season (from August to October).
Both the search for mates, pairing, an act of copulation and the birth of the offspring take place in the treetops. Usually, a female gives birth to one young per year and feeds it for six months. Since sloths do not build nests, their offspring are attached to the mother’s body until they grow up. Sloths reach sexual maturity after three years.
Sloths are solitary, except for females with their young.
They are peacefully disposed to the surrounding world, and they do not need to defend themselves because they are rarely attacked. Sloths do not fight among themselves and live in treetops with monkeys.
Sloths are very resistant to infections.
Even serious injuries do not end with an infection, unlike other animals or humans under these climatic conditions. Learning about this resistance mechanism would allow it to be used in human medicine.
Sloths are excellent swimmers.
It is essential during the periodic flooding of large rivers. They can last up to 40 minutes underwater without taking a breath.
They have feeble sight and hearing.
Their best-developed sense is taste.
They do not need a special water source to quench their thirst.
All they need is dew or raindrops.
Sloths have nine cervical vertebrae, while most mammals have seven.
It allows them to rotate their head 180 degrees.
The biggest threat to sloths is the deforestation of South America.
South American Indians also hunt them for their meat.