The Very Slow Sloths

       The famous French naturalist Buffon selected sloths as the very type of imperfection in nature when he said, “One more defect and they could not have existed.” When talking about sloths we should remember that there are two kinds: the ai or tordo having three toes on each fore foot, and the unau or two-toed form. Both inhabit the forested lowlands of tropical America.

       The more backward and clumsy are the three-toed sloths which may be fairly common although difficult to discover. For one thing they are sort of camouflaged. Except for the three orange-colored patches on the males, one around each ear and a third in the middle of the back, both sexes are a grayish color. This protective color is aided by the growth of a green algae on the hair of the animals. When rolled up in a ball asleep the coloring is so deceptive that the animals may be mistaken for plant parasites, ants' nests—anything but animals.

A two-toes sloth feeding in Manuel
Antonio National Park in Costa Rica.
What's the hurry? (San Diego Zoo)

       One of the most curious features of a sloth is its method of locomotion. When moving around the creature is sometimes actually hanging upside down from the branches. On the ground it is almost helpless, although it can creep slowly and painfully to the nearest tree. Curiously enough the sloth is a good swimmer, so during the early part of the wet season when migrations take place a view of one in the water is not unusual. During the remainder of the year each remains in a rather small area entirely alone except during a very brief mating period.

       Almost every sloth story tells us that the animal sleeps upside down as well as walking in that fashion. More recent studies, however, tell us that the three-toed sloth sleeps in a sitting posture on a branch. The legs encircle the trunk while the head is curled down on the breast so as to be entirely out of view. The short, stubby tail is remarkably strong and flexible; it is used as a prop, and also to sit on when sleeping.

       When danger threatens the sloth may try to bite or claw, or it may curl up into a ball and remain quiet. It can neither fight well nor run away. Some are killed by bird, snake, and mammal enemies, but many escape. The color of the animal seems to be its best protection; also its double coat of thick hair and very tough skin. In addition, it is able to recover from wounds that would kill most animals.

       Food consists entirely of vegetation and almost exclusively of the leaves, buds, and shoots of the cecropia palm. The sloths have never been seen to drink. Their lives are spent in leisure and speed is unknown even when danger is at hand. Sloths seem to have no intelligence whatsoever, and even their senses are poorly developed. Sight is so poor that a mother fails to see her young only a few feet away; hearing is worse, although for short, distances they can distinguish their own peculiarly tuned cries. The other senses are poorly developed also, even smell which is the best of all. Since the three-toed sloth will not adapt itself to a strange diet, it is unsuited for captivity in northern countries.

       The unau or two-toed sloth has a much better all around development. Perhaps the thinner coat of hair is responsible for this, because with a poorer protection the animal would have to be quicker and more alert, otherwise it would soon be killed off. Instead of half clinging, half sliding down a tree feet first, the two-toed sloth is able to descend head first.

       On the ground the two-toed ones can actually walk upright if there is short grass to clutch. Another difference is that this variety is absolutely tailless. When eating they can pull the leaves from the tree and hold them in their claws, whereas the three-toed sloths eat directly from the tree.

       Almost all known animals have seven vertebrae in the neck. The sloths are exceptions, however, the three-toed having nine such bones, and the two-toed possessing six.

       Some of the extinct ancestors of the sloths were enormous creatures. The gigantic Megatheria or ground sloths attained a size almost as great as that of modern elephants. In addition to feeding on leaves and shoots they utilized their long front claws in digging roots for food. These giants originated in South America, but before dying out they had reached North America also. Some of them lived so recently that in a Patagonian cave, in addition to a skull, some of the actual skin was discovered. In fact, a British expedition set out to discover if any of them were still alive.

       So although gigantic sloths have lived in the past, only the small sloths are in existence now. Potter.

• Concerning The Slowness of The Sloth Poem

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