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Zebra - Pyjamas and other theories

Avatar of inke inke - 19. mai 2017 - Discover Namibia

Stripes merge individuals into a group. Photo: Ron Swilling

White stripes on a black background or black stripes on white? Although our perceptions may differ, we can all agree that the zebra has one of the most striking coats seen in the animal kingdom. 

Two species of zebra occur in southern Africa: Burchell's (or plains) zebra Equus burchellii and mountain zebra Equus zebra. Both Burchell's or plains zebra and the mountain zebra subspecies, Hartmann's mountain zebra Equus zebra hartmannae, which is listed as vulnerable on the IUCN (International Union for Conservation of Nature and Natural Resources) Red List of Threatened Species, are found in Namibia. (The Cape mountain zebra is restricted to reserves in South Africa.) 

Although the pied colouring serves to camouflage Hartmann's zebra in mountainous areas, they are clearly visible in grasslands, accentuated against the tawny shades of other antelope species, bringing into question the evolutionary purpose of the stripes. Many hypotheses have been put forward over the years. Children are often told that zebras are horses wearing pyjamas, while African legends tell of Zebra falling into a fire while challenging Baboon, burning the well-known stripes onto his skin. 

From a scientific point of view, zebra stripes have the more practical and life-affirming purpose of deterring predators. When viewed from a distance stripes merge, making it difficult for a predator to distinguish a single animal from the group. This is a definite advantage for herd animals. Because predators will always try and single out an individual animal, a zebra's safety depends on tight bunching. This trait can be seen in breeding groups when the mares and foals keep to the front and the stallion takes the rear. 

Stripes may also serve to confuse a predator as they narrow towards the head, neck and shoulders, widen towards the rump and break the outline of the animal, presenting a distorted image, making it difficult for the predator to judge the size, distance and direction in which the zebra is moving. The stripes also enable zebras to follow one another at night in poor visibility and amidst dust thrown up by their hooves when the big cats are out on the prowl. 

Zebras are preyed upon by lion, leopard, cheetah, hyaena and wild dog, animals that hunt using different methods and at different times of the day and night, making overall protection important at all times. 

Experiments reveal that zebras are attracted to stripes and find them visually stimulating. They are thus genetically programmed to ensure that as herd animals they remain together. Some scientists also believe that because colours absorb or reflect heat at different rates, black and white stripes may create a convection current, having a cooling effect. 

An interesting evolutionary hypothesis suggests that the zebra developed stripes over time to allow it safe passage down the African continent through tsetse fly areas. Stripes deter the blood-sucking pest that targets large surfaces. This may explain why the predecessors of the zebra managed to survive in Africa, unlike those of other Equus groups. (Domesticated horses were introduced much later by early settlers.) 

In the wild, survival tactics take all forms and shapes and animals have perfected methods to ensure their survival. If solitary - camouflage, stealth and silence provide protection, and if sociable, safety is often found in numbers. In addition, some animals have built-in weapons such as horns, and others, like zebras, depend on their colouration and patterning - their dazzling black and white pyjamas - to baffle the enemy.

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