Even-Toed Ungulates: Artiodactyla
EVEN-TOED UNGULATES: Artiodactyla
Because there are as many as 227 species of artiodactyls (ar-tee-oh-DACK-tuhlz), they vary greatly in physical characteristics. The smallest is the mouse deer, which weighs less than 2 pounds (1 kilogram) and stands up to 14 inches (35 centimeters) to the shoulder. The hippopotamus is the largest, weighing in at nearly 10,000 pounds (up to 4,500 kilograms). Head and ear sizes and shapes vary, as do neck lengths, but the eyes are usually big, with long lashes. Tail and leg lengths vary, and fur can be short or long.
Ungulates (UNG-gyuh-luhts) are hoofed mammals. What makes artiodactyls different from perissodactyls (puh-RIH-suh-dack-tuhlz), is the number of toes. With the exception of two species, all artiodactyls have an even number of toes (two or four) on each foot. The hooves are hard and ideal for fast running, though they vary in size depending on the size and mass of the animal. Almost all species have weapons, including horns, antlers, and tusks or canines (the four pointed teeth near the front of the mouth, two on each jaw).
Artiodactyls' coats have two layers: a short underfur and longer guard hairs on top. The top hairs repel water, and the two layers together help control body temperature. Most species have glands that are used for communication. These glands secrete strong-smelling chemicals and substances. The animals use these to mark territory. Animal behaviorists agree that the role of these glands in general is not completely clear.
Artiodactyls can be found on every continent except for Antarctica and Australia. They also do not inhabit oceanic islands.
Habitats vary greatly. Regardless of biome, though, every artiodactyl needs abundant vegetation in order to survive. These animals are found in valleys and on mountaintops, in deserts and tundras. Depending on the species, they will choose habitats that will protect them as they go about their daily activities. For example, bighorn sheep live in open grasslands and meadows near cliffs. The meadow allows them to feed while the cliffs provide security from predators, animals that hunt them for food.
Except for two species, artiodactyls are herbivores (plant eaters). This is probably one of the reasons the order has thrived—vegetation is an abundant food source in almost any ecosystem, and so these animals are able to live almost anywhere.
All artiodactyls have at least one "false stomach" located in front of the actual stomach. Some have three. These false stomachs aid digestion. Because mammals don't have the enzymes that make digestion of plants possible, they rely on microorganisms to help break down plant tissues. These microorganisms, in combination with the action of false stomachs, make for highly effective digestion. Artiodactyls are ruminants, meaning they chew their food, swallow it, then regurgitate (re-GER-jih-tate; vomit) it back into the mouth to be chewed another time.
BEHAVIOR AND REPRODUCTION
Though often seen in pairs or trios, artiodactyls are social and live in groups. Adult sexes live separately for most of the year (though they may share a range), and offspring live with females. Males tend to live where food is more plentiful because they require more energy due to their larger size. Females, on the other hand, tend to live in areas that are more protected from predators because they have the responsibility of raising the young, which are susceptible to predation during the first few months of life.
Artiodactyls are equipped with horns or antlers used for fighting, but physical confrontation is risky because it requires energy that could be used for mating or feeding. Because of this, many artiodactyls will use displays, or behaviors, such as vocalizations or postures, to force an opponent to withdraw. During these displays, the animals do their best to appear as big as possible by raising their fur or standing sideways. They seem to use color patterns in their communications as well, though to what degree we do not know. For example, white-tailed deer raise their tails as a warning signal to other deer that danger is near. This exposes the long white hairs on the rump
THE BUSHMEAT CRISIS
Many of the world's tropical forests are hunting zones for bushmeat (wild meat). Not only does the meat sustain people because it is a food source, but also because bushmeat hunting is the livelihood of local people. Where once bushmeat hunting was on a smaller scale, involving only low-impact technologies, it is now a booming international business, and one that can no longer be sustained.
According to the Overseas Development Institute (ODI), there are many reasons why bushmeat hunting is no longer a sustainable activity. Some of them are:
- Remote tropical forest areas are being opened up at an alarming rate through logging. Whereas inhabitants who live there once existed without interaction in the modern world, they are now being given access to a cash economy and modern consumer markets. No longer are inhabitants native to the area, but often landless migrants searching for work.
- Many forest people have lived in a trade economy one in which they bartered or traded goods and services. Now that they are being forced into a cash economy, there may be the tendency to over-exploit their natural resources so that they can participate in the economy. Bushmeat hunters may begin to overhunt so that they can provide large quantities of the wild meat to wholesale resources.
- New hunting technologies are killing bushmeat animals at a faster rate than they are able to reproduce, thus decimating the herd numbers. This is what leads to extinction.
The bushmeat crisis has become such a concern that in 2004, the ODI began a project titled "Wild Meat, Livelihoods Security and Conservation in the Tropics." The project's aim is to consider the bushmeat crisis in terms of livelihood for humans as well as conservation for the environment and animals.
and underside of the tail, so as it waves the tail from side to side, the stark white contrasts with the darker fur and surroundings, such as plants, trees, etc.
Most species give birth to one or two young at a time. The pig is the exception, with four to eight young born each pregnancy. Artiodactyls breed once a year, and babies are usually born just as plants start to bloom. This allows plentiful food for mother and baby, which ensures nutrient-rich milk for the mother and a long growing period for the newborn.
Babies are able to walk and even run within hours of birth, and they either hide when mother is away or stay close to her during the first few weeks of life. Those who hide include the smaller species. The larger species live in more open habitats and have fewer places in which to hide.
Male artiodactyls mate with several females each mating season, and they usually do not form bonds. Pregnancy lasts from five to eleven months, depending on the species. Artiodactyls are ready to breed at eighteen months of age, and females give birth for the first time around the age of two. Artiodactyls can live to be ten to thirty years old, but the average age of death is much lower. Because of their keen senses and ability to run fast, artiodactyls don't often fall prey to other animals.
ARTIODACTYLS AND PEOPLE
For as long as people have inhabited the earth, artiodactyls have been hunted for their meat and skins. Still today they are valued as a source of animal protein. Domestic livestock such as cattle, pigs, goats, and sheep are artiodactyls. Historians believe sheep and goats were the first artiodactyls species to be domesticated, around nine thousand years ago. Whether domesticated or wild, humans still rely on artiodactyls for meat, bones, horns, fertilizer, milk, and other byproducts.
One hundred sixty species of Ariodactyla are on the IUCN Red List of threatened mammals. Two are Extinct in the Wild; seven are Extinct; eleven are Critically Endangered, facing an extremely high risk of extinction; twenty-six are Endangered, facing a very high risk of extinction; thirty-five are Vulnerable, facing a high risk of extinction; sixty-six are not currently threatened, but could become so; and thirteen are Data Deficient, not enough information to make a determination.
Threats include poaching (illegal hunting), habitat loss from deforestation and agricultural conversion, and competition with livestock. Regardless of the threat, all are based on human demands for natural resources that are slowly disappearing.
FOR MORE INFORMATION
Nowak, Ronald M. Walker's Mammals of the World, 6th ed. Baltimore: Johns Hopkins University Press, 1999.
"Order Artiodactyla." Ultimate Ungulate. http://www.ultimateungulate.com/Artiodactyla.html (accessed on July 9, 2004).
"Artiodactyls." Enchanted Learning. http://www.enchantedlearning.com/subjects/mammals/classification/Artiodactyls.shtml (accessed on July 9, 2004).
"Artiodactyls." GeoZoo. http://www.geobop.com/mammals/art/index.php (accessed on July 9, 2004).
Myers, P. "Order Artiodactyla." Animal Diversity Web. http://animaldiversity .ummz.umich.edu/site/accounts/information/Artiodactyla.html (accessed on July 9, 2004).
The Nature Conservancy. http://nature.org (accessed on July 9, 2004).
"Wild Meat, Livelihoods Security and Conservation in the Tropics." Overseas Development Institute. http://www.odi-bushmeat.org (accessed on July 9, 2004).