The Upside-Down World of the Sloth
WHAT is that old mop doing in the crotch of this tree?’ How surprised the questioner was to learn that what he took to be an “old mop” was in reality an animal—mammal! For the first time in his life he had seen a sloth in its native habitat.
Sloths live in the tropical forests of South and Middle America. They are among the slowest of all creatures. This sluggishness is attributed to their low body temperature. For most of their lives sloths hang upside down from limbs, sit in the fork of a tree or rest their backs on a lower limb. Whenever they are in the trees, their claws are always hooked with a viselike grip to a branch. For sloths, eating, sleeping, yes, even mating and giving birth, are all upside-down activities.
Usually only one baby sloth is born at a time. The youngster might appropriately be described as a ball of fur. Carried by its mother on her chest, the baby clings to her long hair.
Full-grown sloths are about the size of large domestic cats. Their long arms and legs terminate in curved claws, measuring about three inches in length. The coarse hair of the sloth runs the opposite direction to that of other mammals, from the belly to the back.
There is something else that is quite different about the hair of the sloth. You may have heard the expression, ‘A rolling stone never gathers moss.’ But can you imagine an animal that is so slow that plants begin to grow in its hair? Well, that is the case with the sloth. During the rainy season, algae flourish luxuriantly in the sloth’s hair, giving it a greenish tinge.
Besides supporting this plant growth, the hair of the sloth may provide shelter for an insect—a moth resembling a clothes moth. The reason for this is still a mystery. The International Wildlife Encyclopedia notes: “No one has been able to find out why the moths live in sloths’ hair. They do not feed there, nor have their eggs or caterpillars been found in the fur.”
The whole life of a sloth appears to be in slow motion. About eighteen hours of the day sloths doze or sleep, being most active at night. For a sloth to cover a distance of four miles as it moves hand over hand, deliberately attaching each set of claws to tree limbs, may take more than a month and a half. On the ground the sloth’s movement is even slower, as it is mainly designed for an upside-down existence in the trees and not for walking. After getting a hold with its claws, the sloth drags itself forward. What may take seven seconds for the animal in the trees may take a whole minute on the ground. Amazingly, though, sloths are fastest in water. Bodies right side up, they swim by swinging their arms alternately. Sloths have been known to cross bodies of water a mile or more wide.
One might think that a creature as sluggish as the sloth could hardly have survived to the present time. But it is not helpless. The animal is able to defend itself with its long claws and its sharp teeth. Viewed from the ground, a sloth can easily be mistaken for a termite nest or a clump of dead leaves. So the animal may often escape detection by predators. Additionally, tough skin, a heavy coat of coarse, shaggy hair and twenty-three pairs of ribs contribute their part in protecting the animals vital organs. What is especially amazing about sloths is their ability to survive wounds, beatings and even doses of poison that would kill other mammals.
Two Basic Kinds
Why not take a closer look at the unusual sloth? Note the long arms. If each of the arms terminates in two long curved claws, you are examining a two-toed sloth. The longer arms of the three-toed sloth are equipped with three curved claws, as are each of the legs of both varieties.
There are yet a number of other features distinguishing the two basic kinds of sloths. “Two-toes” is larger and tailless. “Three-toes,” on the other hand, has a stumplike tail and is equipped with two or three more vertebrae in its long neck. The total number of vertebrae—nine—is unusual for mammals, nearly all of which have seven neck vertebrae. “Three-toes,” because of having more neck vertebrae, can hang upside down and yet keep its head nearly right side up. It is capable of turning its head through an arc of 270 degrees, almost full circle!
Commenting on a feature that is unique to the male of the three-toed sloth, the work The Animal Kingdom states: “An extremely odd thing about the males is the bright-yellow spot, about the size of a silver dollar, on the back. In this one spot the hair is short and glossy; so far no one has come up with an explanation for this strange feature.” Here, then, is another mystery about the sloth that is begging to be solved.
“Three-toes” has not fared well in zoos. This is mainly because its diet is confined to the buds, leaves and tender twigs of the Cecropia tree. Not as restrictive in its eating habits, “Two-toes” has adapted far better to captivity.
Of the two basic kinds, “Two-toes” is the more active. When threatened, it will quickly strike with its long arms, inflicting serious wounds with its curved claws. It can also bite viciously with its full set of eighteen teeth. Faced with similar danger, “Three-toes” swings its arms more slowly and seldom bites.
“Two-toes” is also less awkward than its relative. It makes its descent from a tree head first. But “Three-toes,” when moving from a limb to the tree trunk, first turns around and then proceeds backward down the tree.
Strange, yet fascinating, is the upside-down world of the sloth. Perhaps you have seen one or more of these creatures in a zoo. On the other hand, at some time in the future you may visit the tropics of Middle or South America. Should that be the case, do not be surprised if what appears to be a dead object up in a tree begins to stir. It may well be that slow-moving sloth enjoying life in his native upside-down world.