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Posts Tagged ‘equus zebra’

Striking, with their distinctive black and white stripes, zebras form part of the wonderful array of African wildlife that makes a visit to a national park or a hike through the mountains so fulfilling. A visit to an Etosha waterhole wouldn’t be the same without our attractive equine friends, nor would a walk through the Fish River canyon be as wild or wonderful without the clattering sound of hooves on rock as a zebra group escapes to the safety of a lofty vantage point.

Although a zebra has a unique pattern of stripes as each person has his/her own individual fingerprints, it is possible to distinguish between the two southern African species at a glance. (The third zebra species, the larger and more mule-like Grévy’s zebra, inhabits the semi-arid grasslands of Ethiopia and northern Kenya.) Burchell’s or plains zebra and mountain zebra have more than their environments to separate them.

Equus zebra hartmannae (7 Cent), issued in 1980, artist: Paul Bosman

Equus zebra hartmannae (7 Cent), issued in 1980, artist: Paul Bosman

The most obvious way to tell the difference between the two is by their stripes. The mountain zebra subspecies, Hartmann’s zebra, like the Cape mountain zebra of South Africa, has solid stripes while Burchell’s zebra, seen in abundance on the grasslands of Etosha National Park, has additional faint stripes superimposed on the white and referred to as shadow stripes. On closer observation, it will be noticed that the Hartmann’s zebra stripes don’t join on its stomach and continue down to its hooves, whereas Burchell’s stripes extend onto its underparts and often fade towards its hooves.

There are two more obvious differences. Hartmann’s zebra Equus zebra hartmannae has a grid-iron pattern across the top of its rump and a prominent dewlap on its throat. Equus burchellii lacks both of these features.

The stripes tell the difference between Hartmann's and Burchell's zebra (below). Photo: Ron Swilling

The stripes tell the difference between Hartmann's and Burchell's zebra (below). Photo: Ron Swilling

Sometimes overlapping, the two species favour different habitats. Burchell’s zebra prefers arid savannah with access to water, while Hartmann’s is found in central and southern Namibia in the rugged terrain of the mountain escarpment and adjacent flats.

Hartmann’s zebra live in small breeding groups of four to five animals comprising one stallion with his mares and foals. They are difficult to spot against their mountain terrain but evidence of their presence is seen in their kidney-shaped droppings, the zebra paths that meander up mountains and their rounded tracks that are etched into the dusty soil. A barking ‘kwa-ah’ alarm signal can sometimes be heard as a group agilely negotiates a koppie. The stallion stands for a few moments behind his family as the rear-guard before trotting off with the others.

Burchell's zebra. Photo: Ron Swilling

Burchell's zebra. Photo: Ron Swilling

The better known species, Burchell’s zebra, is more social than its shyer cousin, congregating in large groups where there is good grazing and often grazing alongside other species like blue wildebeest. Being habituated to people in Etosha, the herds provide ample opportunities for photographs and to observe wild equine behaviour.

These odd-toed ungulates are the quintessential African animal. Their apparent healthy plumpness even during drought, partly caused by the fermentation of bacteria in their gut, adds to our glimpses of an Eden from long ago. The feisty equids are hardy survivors in the fluctuations of the natural world where the eyes of predators are never far away. A new-born foal can stand within fifteen minutes and can run with the herd within hours of its birth. In addition to the protection that their striped patterning may allow, their powerful kick can deter a lion, break a jaw or kill a spotted hyena.

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White stripes on black 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 zebra and the mountain zebra sub-species, Hartmann’s mountain zebra Equus zebra hartmannae, which is listed as vulnerable on the IUCN Red List of Threatened Species, are found in Namibia. (The Cape mountain zebra is restricted to reserves in South Africa.)

Although zebras’ pied colouring serves to camouflage Hartmann’s zebra in mountainous areas, it often seems to be clearly visible in grassland, accentuated against the tawny shades of the antelope species, posing the question as to the evolutionary purpose for zebra stripes. Many hypotheses have been voiced over the years. One of the more naive explanations we receive as children simply describes zebras as horses wearing pyjamas, while the African legends have a tale about Zebra falling into the fire while challenging Baboon, burning the well-known stripes onto his skin.

Stripes merge individuals to a group.  Photo: Ron Swilling

Stripes merge individuals to a group. Photo: Ron Swilling

It has been suggested, however, by those with more of a scientific bent that zebra stripes have a more practical and life-affirming purpose, to deter predators. Stripes merge when seen from a distance, making it more difficult for a predator to distinguish a single animal from the group, a definite advantage for herd animals. Because predators will always try and single out an individual animal, zebras’ 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 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, finding them visually stimulating, another mechanism programmed into their genes to ensure the herd animals 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, keeping them cool.

Zebras (10 Cent), issued in 1983, artist: Jacobus Johannes 'Koos' van Ellinckhuijzen

Zebras (10 Cent), issued in 1983, artist: Jacobus Johannes 'Koos' van Ellinckhuijzen

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 the 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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