Sloths, Anteaters, and Armadillos: Xenarthra

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SLOTHS, ANTEATERS, AND ARMADILLOS: Xenarthra

PHYSICAL CHARACTERISTICS

The order Xenarthra consists of sloths, anteaters, armadillos, and the extinct glyptodonts. The glyptodont, which became extinct 10,000 years ago, belonged to the armadillo family. It was 10 feet (3 meters) long. Modern-day xenarthrans (ZEN-arth-ranz) range from the pink fairy armadillo, which is 6 inches (15 centimeters) long, to the giant anteater, which is up to 7 feet (2.1 meters) long.

Sloths move slowly and spend most of their lives upside down in trees. They hold onto branches and trunks with their long limbs. Sloths have small heads, slim bodies, and tiny tails. Their hair is long and rough. Fur is mainly gray or brown, with green coloring in the outer hair. The green color is caused by algae (AL-jee), which are tiny water plants. Sloths aren't bothered by algae growing in their fur. They lick the algae when hungry, and the color helps sloths blend in with trees. This camouflage (KAM-uh-flaj) protects sloths from predators, animals that hunt them for food.

Two-toed tree sloths are up to 3 feet (0.9 meters) long and weigh 18 pounds (8 kilograms). There is a claw, approximately 3 inches (7.5 centimeters) long, on each of two digits (toes) of the sloth's front feet. Three-toed tree sloths are about 2 feet
(0.6 meters) long and weigh 11 pounds (5 kilograms). They have three digits with claws on the front feet.

In the anteater family, two species have tiny heads and long snouts. The giant anteater and tamandua (tuh-MAN-duh-wah) use their tube-shaped snouts to dig into ant nests, and lick up ants with their tongues. The giant anteater weighs up to 88 pounds (39 kilograms) and its tongue is 2 feet (0.6 meters) long. The anteater's long, coarse fur is black, white, gray, and brown. Because its claws are long, the anteater walks on the side of its feet.

Tamandua is the scientific and common name of the lesser anteater. Length ranges from 3 to 5 feet (0.9 to 1.5 meters), and weight ranges from 8 to 13 pounds (3.5 to 6 kilograms). The northern tamandua is brown with black fur on its back. Southern tamandua fur color ranges from blonde to brown.

Tamandua and the silky anteater have prehensile tails that they use to hold objects or hang onto trees. The silky anteater is up to 20 inches (50 centimeters) long and weighs 17 ounces (480 grams) and up. Its fur is soft, and colors range from gray to yellow. In comparison to its size, the silky anteater's mouth is larger than that of other anteaters.

Armadillos' size ranges from the tiny fairy armadillo to the giant armadillo, which is 4.9 feet (1.5 meters) long and weighs 66 pounds (30 kilograms). Armadillos have long tails, and their bodies are covered by shells, "armor" formed out of bony plates. Hair grows between the plates, and the number of these bands varies by species. Shell color includes brown, white, and yellow. Body color is usually gray or brown. However, the pink fairy armadillo has a pink shell and white body. The armadillo shell covers most of its body.

GEOGRAPHIC RANGE

Xenarthrans originated in the New World and live primarily in Central and South America. Sloths, anteaters, and armadillos live in Bolivia, Brazil, Colombia, Costa Rica, French Guiana, Guyana, Nicaragua, Panama, Peru, Suriname, and Venezuela. Sloths are also found in Ecuador and Honduras. Anteaters range in Belize, Guatemala, El Salvador, Honduras, Suriname, Paraguay, and Uruguay. Sloths and armadillos live in Mexico, and the nine-banded armadillo is the only xenarthran living in the United States.

HABITAT

Sloths live in trees in the rainforest, an area where there is much rain throughout the year. This rain leads to the growth of many trees and plants. Anteaters live in rainforests or in the savanna, an area of grassland with few trees. Giant anteaters live on the ground, and pygmy anteaters live in trees. Tamanduas live in trees or on the ground.

Armadillos live in the rainforest, grasslands, desert, and in deciduous forests where leaves fall off trees during a certain season. Most armadillos burrow, using their claws to dig holes or tunnels that serve as their homes.

DIET

Sloths are primarily herbivores, eating mostly leaves and twigs. Anteaters are insectivores, feeding mainly on insects. Armadillos are omnivores; their diet includes plants, insects, and other animals.

Sloths sleep most of the day and spend about seven hours eating. They develop a taste for the leaves that their mothers eat. This is because the mother sloth carries the cub with her. The young sloth feeds itself by reaching for leaves in the trees where its mother eats. The sloth diet includes leaves, flowers, buds, and twigs. Two-toed sloths may also eat bird eggs and insects.

The anteater's name describes its diet. A giant anteater must consume about 30,000 ants each day. The tamandua eats about 9,000 a day, and the silky anteater can eat 5,000 ants in a day. Giant anteaters and tamandua also consume termites. If tamandua can't locate ants and termites, they feed on bees, honey, and small fruit. The pygmy anteater eats beetles and fruit.

Armadillos eat plants and dig into the ground to find insects and worms to eat. They also eat small animals like snakes and frogs. Diet is based on habitat.

BEHAVIOR AND REPRODUCTION

Xenarthrans are usually solitary. However, armadillos sometimes travel in pairs or small groups. Sloths, anteaters, and armadillos are thought to be polygynous (puh-LIH-juh-nus), meaning males mate with more than one female. After mating, the males leave, and the females raise the young.

A female sloth bears one young that she carries with her for up to a year. A female anteater usually gives birth to one cub. Very rarely, twins are born. The cub stays on the mother's back for six to nine months. Females of most armadillo species bear a litter of one to three young. However, some species bear up to twelve cubs.

When the armadillo is faced by predators, it bends its head down to protect its flesh from attack. The three-banded armadillo rolls itself into a hard-shelled ball. Sloths and anteaters use claws as protection. Predators of xenarthrans include jaguars, lions, and humans.

SLOTHS, ANTEATERS, ARMADILLOS, AND PEOPLE

Humans have various relationships with sloths, anteaters, and armadillos. People hunt xenarthrans for food, and they make pets of some species. Sometimes people keep anteaters at home to help get rid of ants. People kill some sloths for their fur pelts. Tamandua is hunted for the tendon, a cord-like tissue that attaches muscle to bone, in its tail. The tendon is used to make rope.

In addition, medical researchers are studying armadillos. They are the only mammals besides humans that contract leprosy, a skin disease. Research on armadillos helps to develop treatment of this condition in people.

AN UNUSUAL ORDER

Sloths, anteaters, and armadillos were once thought to belong to the order Edentata, a word that means "toothless." Some xenarthrans have teeth, and they all have skeletons that are different from other mammals. "Xenarthra" is a combination of Greek words meaning "strange joints." In xenarthrans, three pairs of joints connect some vertebrae (backbone segments) in the backbone. In addition, xenarthrans don't have separate pelvic bones. Pelvic bones are unconnected in the hips of most mammals.

CONSERVATION STATUS

The three-toed sloth, giant armadillo, and pink fairy armadillo are considered Endangered, according to the World Conservation Union (IUCN). These mammals face a very high risk of extinction. Considered Vulnerable, facing a high risk of extinction, by the IUCN are the giant anteater and several species of armadillos in South America. Risk to these xenarthrans is caused mainly by loss of habitat as the rainforest is cleared of trees. Farming and hunting also threaten these populations.