Physical Characteristics of Edentates
The four genera 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. 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, 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, Tamanda tetradactyla and T. mexicana. Both species have three toes, no teeth, and very sharp claws. They are about four feet long, shortsighted, 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. The armadillo, Spanish for "little armored thing", originated in South America more than sixty million years ago. It is found as far south as Argentinean Patagonia, where the pichi, Zaedyus pichi, is very common. One species of armadillo, Dasypus novemcinctus (the nine-banded armadillo), is found as far north as northern Texas. The armadillo is not toothless, but its teeth are simple, rootless pegs at the back of its mouth. The shell covering most of the animal is made up of hundreds of bony plates that are fused together. Across the middle of its back, the armadillo has a hinge that joins together its front and rear sections, which allows the animal freedom of movement. Armadillos can contract and curl up into a ball to cover their unprotected underbellies. A full-sized adult weighs between eight and fifteen pounds. There are nine genera and twenty species of armadillos. The three-, six-, and nine-banded armadillos (the genera Tolypeutes, Euphractus, and Dasypus) get their names fromthe number of bands in their armor. The armor protects the animal from flesh-eating predators. 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, or Bradypus grisues, 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. The two-toed unau, Choloepus hoffmanni, 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.
The Life Cycle and Habitat of Edentata
Solitary habits and a low reproductive rate characterize all three species of anteaters. The young are born one at a time with a gestation period of approximately 190 days. Amother 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 armadillo lives alone, in pairs, or in small groups. It is primarily active at night, and lives in burrows. It is a strong digger, and also a good swimmer despite its heavy shell. If the animal encounters a small stream or water-filled ditch, it usually just walks right across the bottom, under the water. If an armadillo comes to a larger body of water, however, it will swallow enough air to double the size of its stomach. This increased buoyancy then allows the armadillo to swim across. Once across, it takes several hours for the animal to release all the extra air from its body. In some species of armadillo, the mother bears one to twelve identical young, all of which develop from a single egg. The gestation period for armadillos varies from sixty-five days to four months, depending on the species. Armadillos are found in tropical and subtropical regions, primarily in South America. Most species live in open areas, but some live in forests. They have a very good sense of smell that enables them to detect insects up to five inches below the surface of the earth. Armadillos are easily frightened and are very quick to run away from danger. The armadillo is the only animal, besides humans, known to carry leprosy. For that reason it is illegal to sell a live armadillo in Texas. 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 Edentata
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. The fossil record of armadillos includes groups that were about the same size as contemporary species, as well as a South American species, Macroeuphractus, that was at least 6.5 feet long. The skeleton of another ancestor, Pampatherium, found in a deposit in Texas, was as big as a rhinoceros. All of the ancestors of armadillos appear to have been plant eaters. 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.
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