The Purpose of the Zebra's Coloring

The purpose of zebra stripes may have evolved over time.

The zebra's distinct black and white stripes are a well-known pattern throughout much of the world. The exact reason for the stripes is not certain and has been a topic of debate among scientists for years. There are several leading theories, and it is possible that the zebra's unique coloring fulfills more than one purpose.

Zebra Species

There are three species of zebras. Burchell's zebras are the most widespread and numerous. The northern border of their native habitat stretches between the African countries Somalia and Sudan. In the south, their natural range ends between Namibia and Zululand. The mountain zebra, which is the smallest type of zebra, lives in southern Africa. Grevy's zebra is the largest of the three species, standing approximately 4.5 feet tall at the shoulder and have a larger head than any other equine animal. They can weigh up to 1,000 lbs.

Stripe Differences

The pattern, placement and thickness of a zebra's stripes vary by species. Burchell's zebras' stripes form a Y-shaped pattern on the back half of the zebra as they thicken and bend toward the rump. Their stripes continue underneath along their underbelly. The mountain zebra's stripes do not cross their underbelly. Grevy's zebras' stripes are the narrowest of all zebras and they have a black dorsal stripe along the length of their back. The narrow stripes of Grevy's zebras may be caused by the genes that create the stripes not becoming active until later in the growth of the zebra fetus.

Protection From Predators

One popular theory on why zebra's have black and white stripes is the idea that it protects them from predators. In the dark, and at dusk or dawn, it may be harder to pick out zebras from the background because of their stripes. Also when zebras flee together, it may be difficult for a predator that usually follows one particular animal in the herd to do so because of the moving stripes. It would be hard for a lion to determine what direction that zebras were running and to truly key in on one weak zebra.

Tsetse Fly

The tsetse fly is native to Africa and spreads disease. It avoids landing on striped patterns, which has led to the belief that zebra stripes may protect them from the tsetse fly. The tsetse fly seems most adverse to a horizontal stripe, which is found on Grevy's zebras' underbelly.

Spacing and Socialization

According to Jonathon Kingdon, author of "East African Mammals," zebra stripes may have evolved from providing assistance with social grooming to creating positive visual stimuli in foals that allow the zebras to function in a tight group. He suggests that the thickness of the stripes helps to regulate how closely the zebras function, and that groups of horses do not form such tight-knit units.

References

• Davidson College Department of Biology: Why Are Zebra's Striped?
• "East African Mammals: An Atlas of Evolution in Africa, Volume 3, Part B: Large Mammals"; Jonathon Kingdon; 1988
• "The Kingfisher Illustrated Encyclopedia of Animals"; Edited by Michael Chinery; 1992
• University of Miami Department of Biology: How Did The Zebra Get Those Stripes