Anteaters and sloths

Pilosa Facts

Classification:

• Kingdom: Animalia
• Subkingdom: Eumetazoa
• Phylum: Craniata
• Subphylum: Vertebrate
• Class: Mammalia
• Subclass: Theria
• Order: Pilosa
• Family: Myrmecophaga (anteaters), Cyclopedidae (silky anteater), Bradypodidae (three-toed sloths), Megalonychidae (two-toed sloths)
• Genus and species: Anteaters—three genera and four species; sloths—two genera and six species
• Geographical location: South and Central America, with only one species in North America
• Habitat: Anteaters—savanna, parkland, thorn scrub, and forest; armadillos—savanna, pampas, arid desert, thorn scrub, and deciduous, cloud, and rain forests; sloths—lowland and upland tropical forest
• Gestational period: Armadillos—60 to 120 days; sloths—6 to 11.5 months
• Life span: Anteaters—unknown in the wild, twenty-six years in captivity; sloths—twelve years in the wild, thirty-one in captivity
• Special anatomy: Anteaters have long sticky tongues and long tails; sloths have long tails and claws that enable them to hang from trees

Anteaters, sloths, and several extinct species make up an order of mammals called Pilosa (“hairy”), now found only in the Western Hemisphere and chiefly in South and Central America. One species of anteater, the northern tamandua, is found in Mexico as well. Armadillos were once considered part of the same order as anteaters and sloths, but this is no longer the case.

Pilosans live in a number of habitats, including subtropical and tropical environments. Giant anteaters live in grasslands but also can be found in western South American forests. They feed on termites and ants, either at night or during the day. Lesser anteaters live mostly in tropical rain forests and are nocturnal in their habits, preferring to hunt at night. Tree sloths live in trees in humid tropical forests, where they feed exclusively on leaves and plants.

Physical Characteristics of Pilosans

The four species of anteaters share several characteristics: They have long heads, long, tube-shaped mouths with long tongues, but no teeth. They are mammals and belong to the family Myrmecophagidae, except for the silky or pygmy anteater, which belongs to the family Cyclopedidae. The giant anteater, Myrmecophaga tridactyla, is sometimes called the ant bear. It can reach six feet in length and weigh up to eighty-six pounds and lives in swampy areas and open grasslands in South America. It is gray in color with a white-bordered black stripe on each shoulder. It has a long, bushy tail and sharp front claws used to tear open termite nests. The claws are so long that, in order to move, the ant bear must tuck its claws under its front feet and walk on its knuckles. The long, narrow tongue has a sticky surface; it flicks rapidly out of a small mouth and is perfectly suited for licking up termites and ants that adhere to its surface.

The pygmy anteater, Cyclopes didactylus, also called the two-toed anteater or silky anteater, is the smallest of the anteaters. It reaches about fifteen inches in length, but half of that is tail. The pygmy anteater weighs only four pounds on average. It has a small nose and silky golden fur that make it look like the seedpods of the main tree it inhabits, the silk cotton tree. It lives high up in the tree, where it feasts on termites and seldom comes to the ground. It uses its tail to help it jump from tree to tree.

There are two species of Tamandua, or lesser anteaters, Tamandua tetradactyla and T. mexicana. Both species have three toes, no teeth, and very sharp claws. They are about four feet long, short-sighted, and very hard of hearing. Their noses are much shorter than those of the giant anteaters. Both species are shorthaired and brownish, with a black area that looks like a vest on the front side. They live in trees and use their long, prehensile tails to help them hold onto branches. They sometimes come to the ground, where they walk extremely slowly. They do most of their feeding at night, eating ants, termites, and other small insects.

Sloths are arboreal (living in trees), with six species found in the rain forests of Central and South America. They are herbivorous, meaning they only eat plants. There are two main kinds of sloths: the three-toed sloth, called an ai, and the two-toed sloth, known as the unau. The ai got its common name from its cry of distress, “ai-ai.” It is about two feet long, slender, and has long legs. Its feet are armed with three long, hooklike claws, from which it hangs from branches. It has small ears, a tail, and a bullet-shaped head. One unusual feature is its long neck, which contains nine vertebrae, two more than is usual in mammals. Its coat of hair is dull gray and in another peculiar feature, an algae grows in the sloth’s hair that gives it a greenish color, making the animal difficult to see among the green leaves. Three-toed sloths eat only the leaves of the cecropia tree. There are four species of three-toed sloth: Bradypus pygmaeus (the pygmy three-toed sloth), B. variegatus (the brown-throated three-toed sloth), B. tridactylus (the pale-throated three-toed sloth), and B. torquatus (the maned three-toed sloth).

The two-toed unau is larger than the ai. Its neck has only seven vertebrae, and the animal has no tail. It has two claws on its front feet but three claws on its hind feet. Unlike the three-toed sloth, the unau can come down a tree headfirst and stand upright on all four feet. Its diet consists mainly of leaves, stems, and fruits. The eyesight and hearing of all sloths are not very well developed, and they usually find their way mainly by touch. There are two species of two-toed sloth, Choloepus hoffmanni (Hoffman's two-toed sloth) and C. didactylus (Linnaeus's two-toed sloth).

The Life Cycle and Habitat of Pilosa

Solitary habits and a low reproductive rate characterize all four species of anteaters. The young are born one at a time with a gestation period of approximately 190 days. A mother carries a single offspring on her back for most of its growth period, which can last up to a year in the case of the giant anteater. The giant anteater lives in the grassland and forest of South America; it is the only anteater that lives on the ground. It is an excellent swimmer, however, and is frequently seen in the Amazon River. When it lives near human populations, it is active only at night, but in the forest it can be found hunting ants and termites during the day. Its home is an old burrow abandoned by another animal, or a hollow log. The giant anteater is becoming rare due to the trade in exotic pets and through the destruction of its habitats.

The pygmy anteater rarely comes down from the tall trees it lives in, and is active only at night. It lives high up in trees in the rain forest and feeds on termites. Its breeding habits are not known. The lesser anteater lives in trees, hanging on to branches with its tail. It emerges at night to eat insects, ants, and termites. Its breeding habits also remain unknown. Lesser anteaters are hunted for their tails, which are used to make rope, and native Brazilians sometimes bring them into their homes to rid them of termites.

The tree sloth usually lives alone and spends most of its time sleeping. The brief time that remains, it spends eating leaves and moving about. It sleeps hanging by its tail from a branch, with its feet bunched together and head tucked into its chest. Its greenish color makes it look like a bunch of dead leaves, making it almost invisible to other animals. Even at night it moves slowly, so as not to attract the attention of its enemies.

Sloths do not make nests, and sleep wherever they happen to be. They are not aggressive, but if two males come together in the same area during mating season, they will fight until one is killed. Mothers give birth to single young during the summer. The baby lives with its mother, clinging tightly to her breasts for five weeks, and then begins to eat by itself.

Extinct Pilosans

The evolution of the anteater is not clear, but its oldest ancestor is believed to be some unknown form of insect. The three suborders of anteaters were separate for much of their history because they emerged long before North and South America were joined by the Isthmus of Panama, about 3.5 million years ago. All of the North American species died out before that contact was made.

In the past, many varieties of sloths roamed the Americas from New Mexico to the southern tip of South America. They ranged in size from small animals the size of a fox to a giant ground sloth, Megatherium, which was larger than a full-grown elephant. A bear sloth, Nothrotherium, and other extinct members of the sloth family lived in South America about one million years ago. A third family of extinct ground sloths, Mylodontidae, is particularly closely related to the modern two-toed sloth.

Principal Terms

arboreal: living in trees

herbivorous: plant-eating

nocturnal: active only at night

Bibliography

Anderson, S., and J. K. Jones, Jr., eds. Orders and Families of Recent Mammals of the World. New York: Wiley, 1984. Print.

Ceballos, Gerardo. Mammals of Mexico. Baltimore: Johns Hopkins UP, 2014. Print.

Dorst, J. South America and Central America: A Natural History. New York: Random House, 1967. Print.

Tudge, Colin. The Variety of Life: A Survey and a Celebration of All the Creatures That Ever Lived. New York: Oxford UP, 2000. Print.