Horses, Zebras, and Asses: Equidae

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HORSES, ZEBRAS, AND ASSES: Equidae

_GREVY'S ZEBRA (Equus grevyi): SPECIES ACCOUNTS
KIANG (Equus kiang): SPECIES ACCOUNTS
PRZEWALSKI'S HORSE (Equus caballus przewalskii): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

Equids (EH-qwidz; horses, zebras, and asses) are built for speed, with long legs that allow them to move efficiently. Their single stomachs allow them to eat foods high in fiber because digestion occurs rapidly, and their single-toed hooves make navigating over rocks and hard surfaces easy.

There are three species of zebra, and each has a different stripe pattern. All equids have short coats, though those living in higher altitudes may grow thicker coats. There is very little size difference between the sexes.

GEOGRAPHIC RANGE

Equids live in Africa below the Sahara Desert, in the Middle East, Arabia, Central Asia, and Mongolia.

HABITAT

Equids graze throughout the day, and various species live in deserts to grassland and shrubland (similar to grassland, only with small trees and shrubs as well).

DIET

Equids eat grasses high in fiber, which makes them more difficult to chew and digest. Their teeth are made for breaking down the reedy plants, however, and their single stomach allows for quick digestion.

BEHAVIOR AND REPRODUCTION

Equids are social mammals and form groups in which individual needs for feeding, reproduction, and survival are met. Females form especially strong bonds and maintain stable communities even without the presence of a territorial male. Usually, one male heads a group and mates with several of the females. He spends a good deal of his time defending the group against "bachelor" or roaming males who might try to mate with the females. Offspring also live with the group, usually until the age of two or three years.

Groups are in the best interests of equids as they provide greater defense against predators, animals that hunt them for food, like the lion. When in herds, it is more difficult for lions to determine which zebra or horse is young, weak, or lame. When threatened, equids will run away rather than fight, but if forced to fight, they'll kick with their hind feet and bite.

Equids communicate through vocalizations but also by changing the position of their tails, ears, and mouths.

The mating system varies, depending on environmental conditions. Pregnancy lasts from eleven to twelve months and usually results in the birth of one foal. And although equids are capable of producing one foal each year, it is more likely that a foal will be born every other year if nutritional food is readily available. Wild equids are ready to breed at the age of one or two years but don't normally produce a foal until the age of three to five. There is not enough data to determine how long wild equids live. Experts estimate that 90 percent of female plains zebras die by the age of sixteen years. Their main predators are the lion and hyena.

WHY ZEBRAS NEED STRIPES

Although humans think a zebra's stripes make the horse easy to find and identify, the stripes actually act as camouflage (KAM-uh-flaj). The wavy lines of a zebra blend in with the wavy-line patterns found in nature, such as blowing grasses among which the zebra lives. The fact that zebra stripes are black and white while the lines of grass are yellowish green and brown doesn't matter. The zebra's primary predator, the lion, is colorblind!

Those stripes serve another purpose, which is to help zebras identify and recognize each other. Stripes are to a zebra as fingerprints are to humans: no two are identical. Scientists believe this is how zebras identify one another in a herd. It's how mothers and babies recognize each other, and how a zebra knows which herd it belongs to.

EQUIDS AND PEOPLE

Domestic horses have played a significant role in the social and agricultural progress of humankind. Ironically, however, it has been humankind that has decimated the wild equid populations through hunting, habitat destruction, and the demand for livestock farming.

CONSERVATION STATUS

Of the seven species, one is Extinct, died out, in the Wild; one is Extinct altogether; one is Critically Endangered, facing an extremely high risk of extinction; two are Endangered, facing a very high risk of extinction; and one is Vulnerable, facing a high risk of extinction. Wild equids are threatened primarily by hunters, but also by livestock grazing in their habitat, and inter-breeding with domestic horses and donkeys.

GREVY'S ZEBRA (Equus grevyi): SPECIES ACCOUNTS

Physical characteristics: This zebra measures about 9.8 feet (3 meters) in length, with a shoulder height of 5.3 feet (1.6 meters). It weighs around 990 pounds (450 kilograms) and is the largest wild equid. The ears are large and round, and the short coat is black and white striped. The muzzle is white, and there is a dark stripe surrounded by white running down the length of the back.

Geographic range: Grevy's zebra inhabits parts of Kenya as well as southern Ethiopia. It is believed that a small population exists in southeastern Sudan.

Habitat: Grevy's zebras live in grassland, and must live near a permanent water source.

Diet: This zebra eats grasses, but will feed on shrubs and small trees or plants if drought conditions deplete the supply of grasses.

Behavior and reproduction: As with other equids, Grevy's zebra participates in a territorial mating system in which one male resides over a large herd consisting of numerous females and their offspring. Because pregnant and nursing females need water daily or every other day, they are usually located near a permanent water source. This species differs from other zebras in that it doesn't form lasting bonds. In fact, the composition of the herd can change on an hourly basis.

Pregnancy lasts for about thirteen months, and the foal is able to recognize its mother by smell and sight within an hour of its birth. This is also the time it begins to stand up and run with the herd.

Grevy's zebra and people: Grevy's zebra is killed for its meat and hide as well as for medicinal purposes. Although these zebras eat the coarse grasses that livestock cannot feed upon, their habitat continues to be threatened and depleted by domestic livestock, which competes for grazing land.

Conservation status: Grevy's zebra is considered Endangered due to overhunting as well as competition for water and food with people and domestic livestock. ∎

KIANG (Equus kiang): SPECIES ACCOUNTS

Physical characteristics: This medium-sized wild ass stands between 3.3 and 4.7 feet (1 and 1.4 meters) and has a coat that changes with the seasons. It is dark brown in winter and chestnut red in summer. To keep warm, the length of the hair doubles in winter. The belly is white, and there are patches of white on the neck, chest, and shoulder. The muzzle, too, is white.

Geographic range: The kiang (kee-YANG) lives in China, India, Nepal, and Pakistan.

Habitat: This wild ass is found in altitudes up to 16,500 feet (5,000 meters) in grasslands and steppes (regions characterized by grasses and shrubs, with few or no trees).

Diet: The kiang eats primarily grasses and low shrubs.

Behavior and reproduction: Kiang live in close-knit herds ranging from 5 to 400 individuals, which do not scatter. The herd, composed of females and offspring, is led by an older female, and they travel in single file. The herd seems to move in unison (as one), whether they're drinking, eating, or running. Unlike other horse species, kiang do not physically touch one another. They are strong swimmers and enjoy spending hot summer days in water.

Male kiang begin following the female herds in July, and breeding takes place in August. After a year-long gestation (pregnancy) period, females form breakaway herds of two to five and retreat to nearby rocky areas to give birth to single foals. The foals thrive on mother's milk for the first year, after which time they become independent. Kiang live to be around twenty years of age; the main predator is the wolf.

Kiang and people: Kiang are hunted for their meat in some areas.

Conservation status: The kiang is listed as threatened by the IUCN. Kiang populations are most threatened by commercial hunting, habitat destruction, and competition for food and water. ∎

PRZEWALSKI'S HORSE (Equus caballus przewalskii): SPECIES ACCOUNTS

Physical characteristics: This horse stands 4 to 4.8 feet (1.2 to 1.5 meters) tall and weighs around 772 pounds (350 kilograms). Its legs are rather short while the head is large. During summertime, the coat is short and reddish brown, a color also known as "dun." The hairs grow thicker and longer during the winter to provide insulation from the cold. The mane is short and stands straight up, and the top of the tail has short hairs. The muzzle is white with gray around the nostrils.

Geographic range: Przewalski's horse is considered Extinct in the Wild, but has been reintroduced in certain areas of Mongolia.

Habitat: Like the kiang, this horse lives in grassland and steppe regions. It was last seen in the steppes of the Gobi desert.

Diet: Przewalski's horse eats whatever grasses are available.

Behavior and reproduction: These horses form a stable family composed of one male, numerous females, and their offspring. Other males form what is called "bachelor" groups.

After 340 days of pregnancy, females deliver a single foal, usually in April, May, or June. Foals are weaned (removed from mothers' milk) around six to eight months and are ready to breed around the age of two years. Wolves are the primary predators of Przewalski's horse, and it is believed they live to an average age of twenty years.

Przewalski's horse and people: This horse is of great significance to the people of Mongolia as it is their national symbol.

Conservation status: Listed as Extinct in the Wild, though reintroduction into Mongolia has begun. They became extinct due to overhunting, capture by zoos, and loss of habitat. Today, reintroduction is difficult because there are so few left that genetic diversity (variation of genes that create distinct differences within a species) is nearly gone. ∎

FOR MORE INFORMATION

Books:

Dines, Lisa. American Mustang Guidebook: History, Behavior, and State-by-State Directions on Where to Best View America's Wild Horses. Minocqua, WI: Willow Creek Press, Inc., 2001.

Draper, Judith. The Book of Horses and Horse Care. New York: Barnes & Noble, 2003.

Shah, Anup. The Circle of Life: Wildlife on the African Savannah. New York: Harry N. Abrams, Inc., 2003.

Periodicals:

Meadows, Robin. "An Equid Primer." Zoogoer (September/October 1997). Online at http://natzoo.si.edu/Publications/ZooGoer/1997/5/equidprimer.cfm (accessed July 9, 2004).

Moretti, Laura. "Mestengo. Mustang. Misfit." Animals' Voice Online at http://www.animalsvoice.com/PAGES/features/horses1.html (accessed July 9, 2004).