Sloths are sometimes called the slowest mammals on Earth. These arboreal mammals have coarse fur, short necks, long limbs, and long curved claws. Although they remotely resemble primates, they are actually most closely related to anteaters and armadillos.
Once sloths were the size of elephants
Millions of years ago, our planet was inhabited by giant ground sloths the size of an Asian elephant. Some megatherium were almost 6 meters in length from nose to tail and had massive claws. These giant mammals also had small bone discs on certain parts of their bodies, which served as a "shield" for protection. Megatherium became extinct about 10,000 years ago.
Today's sloths are slightly less intimidating than their ancestors. They reach a maximum height of about 76 cm, have a body length of 53-74 cm, and weigh 4-8 kg. A sloth in size and shape is comparable to a small dog.
The sloth's body is long, with a short neck. Four long limbs of equal length end in two curved claws measuring 8-10 cm. The head is small and flat, with a snub nose, large eyes, and rudimentary ears.
There are two types of sloths
There are only two living families: two-toed sloths and three-toed sloths. However, this classification can be misleading, as both types have three claws or "fingers" on their hind limbs. But the two-toed sloth has only two fingers on the front limbs, while the three-toed sloth (as you may have guessed) has three. Two-toed individuals are also slightly larger than their three-toed counterparts.
Sloths - a walking ecosystem
They have a short, thin undercoat and an upper layer of fur consisting of longer and rougher hairs, which in humid conditions acquire a greenish hue due to the growth of algae. In each strand of brown-gray hair, there are grooves running from top to bottom, in which two types of blue-green algae grow.
Sloths have a symbiotic relationship with algae: the animal provides the algae with shelter and water (as the sloth's fur absorbs moisture well), and the algae provide the sloth with a greenish camouflage, masking it in the canopy of the forest, as well as supplying additional nutrients through the skin.
In addition to algae, sloths' fur is inhabited by beetles, mites, and moths. Their hair curves from belly to back; something uncommon in most mammals.
They have a low metabolism rate
These mammals maintain a low body temperature, fluctuating between 30 to 34 °C. It drops during cooler nighttime hours, in humid weather, or when the animal is inactive. This helps the sloth conserve life energy. Its metabolism rate does not exceed 45% of the expected value corresponding to its mass.
It has small musculature, approximately half the relative weight of the vast majority of terrestrial mammals, so it cannot afford to warm itself by shivering. The sloth regulates its body temperature by moving to the sunny side or avoiding sunlight. The nature of the sloth allows it to save energy by moving slower than any other mammal on the planet. The sloth usually covers no more than 38 meters in a day, crawling up to 30 cm per minute.
The American continent - home to sloths
Sloths are found throughout Central America and in the northern parts of South America, including some areas of Brazil and Peru. Sloths are strictly arboreal animals that inhabit high up in the canopy of tropical rainforests. Their range does not exceed four hectares.
Sloths have a leafy, low-calorie diet
Sloths' teeth continuously grow, and they need to wear them down with plant material to prevent them from becoming too long. Their lack of sharp teeth is compensated for by hard lips that cut leaves. Sloths eat leaves, fruits, and fresh green shoots (they don't like crunchy twigs). Although they are primarily herbivores, they can occasionally snack on insect larvae or other passive protein snacks (such as bird eggs). Sloths get water from their food and drink dew from leaves and fruits.
They have a multi-chambered stomach, which allows them to efficiently digest hard cellulose. Food remains in their relatively short digestive tract for about a month. They have a low metabolism rate, and feces and urine are excreted only once a week in familiar spots at the base of trees.
In zoos, sloths eat lots of vegetables, including cabbage, corn, apples, bananas, sweet potatoes, and carrots.
Sloths are caring parents
Female sloths reach sexual maturity at the age of three. They reproduce once a year. Males mature between 4 and 5 years old. After a six-month gestation period, females give birth to small, well-developed offspring measuring 25 cm and weighing 340 grams.
The babies cling tightly to their mother's belly for the first five weeks of life. By 1.5 months, they become strong enough to move independently. Mothers spend a lot of time and energy feeding and caring for them both before and after weaning.
More than half of a sloth's life is spent sleeping
Sloths are primarily crepuscular animals: they sleep for 15 hours during the day and wake up at night to eat. Due to the peculiarities of their metabolism, they use energy sparingly and usually move slowly within small home ranges.
Sloths spend a lot of time on tree branches, hanging upside down from them. In this position, they sleep, eat, mate, or give birth. They only descend to the ground to switch trees, find new food sources, or defecate.
The impressive biology of sloths allows them to spend 90% of their lives in an inverted position. Anatomical studies have shown that this became possible due to the attachment of organs to the chest, meaning they do not press on the lungs. Therefore, unlike humans, sloths can hang upside down without affecting their breathing.
Sloths are quick healers
When it comes to defense against predators, sloths usually rely on their camouflage. They blend well into the treetops, curling up into a ball on a tree branch. In this position, they resemble either a termite nest or a tree branch. This, combined with the green color of their fur, provides excellent protection from predators.
However, in case of discovery, they can use their teeth and claws. And despite their slow movements, sloths are surprisingly strong. Normally silent sloths will start to hiss fiercely or emit low moans, intimidating the enemy.
Jaguars and eagles are the most dangerous enemies of sloths. But even after receiving serious injuries from them, sloths are able to recover quickly. Deep wounds and bites completely heal in less than a month.
Sloths are strong swimmers
Although sloths have long claws that hinder walking on land, they can move in water three times faster. This is quite surprising for such typically slow animals! They are also capable of holding their breath for up to 40 minutes, suppressing metabolism and reducing heart rate by a third.
Sloths have excellent vision
Sloths have an additional vertebra at the base of their neck, allowing them to turn their heads 270 degrees. This gives them the ability to have almost a 360-degree view of their surroundings, which is a very useful defensive mechanism. This unique feature sets sloths apart from other mammals, whose bone structures do not allow such flexibility.
They have a relatively short lifespan
Their average lifespan in captivity is about 16 years. The oldest sloth ever recorded was a female two-toed sloth that lived in the Smithsonian National Zoo for almost 49 years!
Did you know?
- The Pygmy three-toed sloth is the smallest sloth species. Its body length does not exceed 5 cm. It inhabits only a small island off the coast of Panama.
- Sloths are relatively solitary mammals, although sometimes groups of females occupy the same tree. Young individuals can also inherit their parents' homes.
- The sloth's brain is small in size and almost without convolutions.
- In a satiated individual, up to 70% of the weight is attributable to the digestible food in the stomach.
- Sloths are part of the Edentata order, as their teeth do not have enamel covering and roots.
- Many sloth species are threatened with extinction. The most vulnerable is the Maned three-toed sloth.
- The Greek goddess Aergia was an ancient personification of sloths because she also loved to sleep.
