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Sloths: Like No Other Animal Family

Sloths: Like No Other Animal Family


Tree sloths are one of the strangest families one could imagine and seem to have very little in common with any other animal kind (Edmonds, p. 38). They are the world’s only inverted quadruped (Cooke, p. 52). Sloths are almost comically slow-moving mammals, deliberately moving so slowly that it looks like a movie of them is being played in slow motion. Neither prodding nor threats will make them move much faster, partly because when on the ground, their small legs are so weak that they have to drag their heavy middle along the surface (Cooke, p. 51). A tortoise would easily beat them in a race. Their cruising speed is a mere 0.19 miles per hour, but they can climb a tree at a fairly good clip, for a sloth that is.  They often sleep, or appear to sleep, one cannot always tell, about 10 hours a day in trees in the Central and South America rain forests. In contrast to most mammals, they are neither strictly nocturnal nor diurnal, but frequent nappers instead (Hoke, p. 88).

As semi-nocturnal animals, sloths have very large eyes like lemurs. They have poor hearing and comparatively poor sight, and are solitary creatures except for mating and caring for their young. They lack cutting teeth and other defense systems like most mammals. They lack most forms of vocalization except for females that, during mating season, will climb a tree and let out ear piercing shrieks that travel for miles to attract a mate (Cooke, p. 66). Ironically, Hoke claims that they “thrive on human companionship as much as dogs do. Our young daughter found the sloth to be the truest of teddy bears—and one that played back” (Hoke, p 91).

These normal herbivores spend the majority of their time hanging upside down from the branches of the trees they both live in and feed on. They have comical monkey-lemur like faces but are not monkeys. Their faces appear to wear a perpetual silly smile. They live in the branches of many tropical tree types, but their preferred type is the cecropia tree, referred to as the sloth tree for this reason.

The six species are grouped in two families: two-toed and three-toed sloths, which are so similar yet as different as cats and dogs. Thus, they are hypothesized by Darwinists to have co-evolved (Cooke, p. 55). The idea is that these creatures branched some 70 million Darwin years ago, and, evolutionists speculate, their way of life “must have its benefits as it was worth evolving twice.” (Cooke, p. 55).

All sloths actually have three toes, but the three-toed type have three 8-10 cm long hooks, for hanging on tree branches and two-toed sloths have two hooks on each forelimb. Their “digits terminate in huge hooked claws, which are effective structures for suspending the animal from a tree.” (Whittow, p. 60). Their circulatory system is designed like the flippers, fins, and flukes of marine animals. This system is specially engineered to insure good circulation in their hands and feet while spending most of their time upside down (Whittow, p. 62).

The main problem biologists have with both their classification and evolution is that no other animal is like them, not even close. Designed to live upside down, they are nearly helpless when on all fours, which they rarely are (Hoker, p. 89). They eat, sleep, mate, and even give birth upside down while hanging by their three-inch claws that firmly lock onto tree branches.

Even their hair grows upside down, which is necessary to drain water from their body and prevent them from getting soaked. After a rainstorm, their hair parts down the middle which allows rain to easily run off their wiry hair. In all mammals, hair grows toward the extremities, but sloth hair grows away from the extremities. Almost every inch of their body, including their limbs, and excepting only their face and toes, is covered with long, thick coat of hair not like that found on tropical animals but rather Arctic mammals. Their second inner hair coat is very fine downy hair.

The sloth fur can be a small ecosystem of its own. Many sloths have a symbiotic relation with some species of commensal arthropods as well as the blue-green algae (now called cyanobacteria) that thrive on its coat, giving it a greenish color (Perman, p. 35). The algae provide critical nutrients which the sloth absorbs through its skin or by licking its fur.

On the ground, sloths are awkward, but in trees, and even in water, they move slowly, but gracefully. In water, sloths can reduce their normally slow metabolism even further, slowing their heart rate to less than a third of normal. This allows them to hold their breath underwater for up to 40 minutes. They also have an amazing ability to survive severe injuries, such as being attacked by dogs, hit by cars, or zapped by electrical powerlines. Reports include one of falling close to 100 feet to the forest floor without injury and of another surviving for 24 hours in a refrigerator (Cooke, p. 62). How they can survive major trauma that would be lethal to most mortal animals is a mystery. Understanding this feat could be of enormous value to humans.

 Digestive System

One of the most unique aspects of a sloth is its digestive system. Its food source consists of leaves that are very difficult to digest, and some kinds that are very toxic. To utilize this diet its stomach is a “multi-chambered monster much like that found in cows” (Cooke, p. 58). Its food may take as long as a month to digest in its multichambered stomach.

Two-toed sloths have a diverse diet of insects, carrion, fruits, leaves and even small lizards. Conversely, the three-toed sloths usually have a diet limited to leaves from only a few trees. They do not chew very assiduously, and the three-toed sloths even lack front teeth. As a result, the animal requires gut bacteria to break down its barely masticated leaves (Cooke, p. 59). For the gut to work requires a lot of time, clocked by scientists to be a full fifty days from ingestion to excretion.

This, the slowest digestion rate of any mammal, turns out to be ideal because if the digestion was much faster the liver, which detoxifies toxins, could not cope. Self-poisoning could result from the toxins the plants in their diet produces (to protect them from insects) in the food they ingest. Also, the digestion system requires about only ten percent of the physiological work required for a mammal the size of a sloth. Given that their diet provides only about 160 calories for an average day, it is clear that their entire digestive system is very well designed for their lifestyle. Their metabolism, as would be expected, is freakishly low, about half as fast of that expected of a mammal their size. Furthermore, their “blood vessels and throats are uniquely adjusted to swallow food and circulate blood against the force of gravity.” (Cooke, p. 59).

Although not cold blooded, they can deal with rather large body temperature fluctuations that would kill many mammals. One way is to regulate their metabolism rate. The sloth’s body temperature range is greater than that of any other known mammal, from 75 to 91 degrees. They are heterothermic somewhat like reptiles. One reason for the low body temperature is that they have very little muscle mass, thus not much insulation, and their small muscle mass produces less heat than most mammals of their size. Muscles make up only 25 percent of their total body weight compared to most other mammals, which is about twice that of the sloth (Whittow, p. 62). To help keep warm, it can curl up into a ball shape like an armadillo.

Also, like no other mammal, about once a week three-toed sloths climb to the ground to urinate and defecate, digging a hole near the trunk of their tree, helping to fertilize it, then  covering it up afterwards. Some research has concluded this ritual is part of their mating behavior.


Sloths have proved very difficult to classify. Taxonomists did not know where else to put them, so this forced them into the superorder family xenarthral along with two animals that seem to have very little in common with them, anteaters and armadillos. Moreover, the anteaters and armadillos also seem to be so different from each other that evolutionists are baffled as to where all three could have evolved from. So, they were grouped together in one strange unlikely family that is so different they do not even look like distant cousins.

About the only thing these three creatures have in common is an unusually flexible spine (Cooke, p. 56). For example, the three toed sloth can turn their heads close to 270 degrees, in either direction, useful for consuming a meal while hardly moving their body. Their necks are this flexible because they have “more neck vertebrae than any other mammal’s, even a giraffe” (Cooke, p. 62).

No Evidence for Evolution

Darwinists claim they lived at the time of the dinosaurs 65 million years ago (Cooke, p. 60). In spite of being around for a very long time, according to evolutionists, no evidence exists of their evolution (Perman, p. 36). The best guess of Darwinists is that these animals, which are the size of a house cat, are related to non-arboreal land dwelling animals about the size of bears. Another guess is they are related to a Megatherium, an extinct species about the same size as an elephant.

They are clearly “an aberration of evolution” (Cooke, p. 54). Although the scientific literature on the animal is sparse, we know more than enough to conclude that no better evolutionary common ancestor has been located after decades of looking, leading to the conclusion that the first sloth was a sloth (Hoke, p. 92).


Cooke, Lucy.  2018. The Truth About Animals. New York: Basic Books.

Edmonds, Patricia. 2018 The Joy of the Chase. Or sex at high Speeds. National Geographic.  234(1):38. July.

Hoke, John. 1987. Oh, it’s so nice to have a sloth around the house. Smithsonian. 18(1): 88-90.

Perman, Craig. 2016. The Sloth. Creation 38(4): 34-37.

Whittow, G. Casey. 1977. Night Shift for Sloths and Other Sluggards. Natural History. 87(1): 66-73. January.

Jerry Bergman
September 2018

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