Distinguishing stripes

Kruger National Park | November 2018

The zebra is one of the iconic animals of Africa and is one of the creatures that people on safari are keen to see. They are extremely beautiful animals, with their black and white striped patterns. Zebras belong to the family Equidae and the plains zebra, which we find in our area, falls in the genus Equus. They are diurnal, black and white, striped, plains-loving, grass-munching horses of the African savannas!

Zebras and horses belong to the order Perissodactyla (odd-toed ungulates). Perissodactyls all share hooved feet and an odd number of toes on each foot, as well as mobile upper lips and a similar tooth structure. This means that zebras and horses share a common ancestry with tapirs and rhinos.

Today there are three species of zebras in Africa. These are the plains zebras (Equus quagga), the mountain zebras (Equus zebra) and the Grevy’s zebra (Equus grevyi). In southern Africa we only find plains zebras and mountain zebras. Grevy’s zebras are found in East Africa (Kenya and Ethiopia).

The plains zebra found in the Kruger National Park is considered a subspecies called a Burchell’s zebra. Its scientific name is Equus quagga burchellii and the word quagga refers to the zebras’ distinctive ‘kwa-ha’ call (the word quagga also refers to a distinctly coloured subspecies of plains zebra that was found in the Cape region but was hunted to extinction in the late 1800’s), while the word burchellii is a reference to John Burchell, the naturalist and collector who explored the interior of South Africa between the years 1810 and 1815. The subspecies of plains zebra known as the Burchell’s zebra is easily identified by the brown “shadow-stripes” that can be seen, particularly on the rump area.

In southern Africa there are two sub-species of mountain zebra. These are the Cape mountain zebra (Equus zebra zebra) and the Hartmann’s mountain zebra (Equus zebra hartmannae). Cape mountain zebras were formerly widely distributed in the mountain ranges of the Eastern and Western Cape. Due to hunting pressure this species was almost extinct in the mid-1930’s, and was saved by the proclamation of the Mountain Zebra National Park, in the Cradock district of the Eastern Cape Province, in 1937. Today only three naturally occurring populations of Cape mountain zebras still exist, namely in the Kamanassie mountains, the Gamka mountains and the Mountain Zebra National Park. The Hartmann’s Mountain Zebra is predominantly found in dry semi-desert areas of Namibia.

The big differences between the plains zebras and the mountain zebras are: the stripes of the plains zebras stretch all the way to the belly, whereas the mountain zebras have white bellies. Mountain zebras also have a flap of skin on the throat known as a “dewlap”, which plains zebras do not have. The stripes of the mountain zebras go all the way down the leg to the hoof, whereas the lower part of the leg of the plains zebra is much paler. Another big difference is that the mountain zebras have a grid-iron pattern across the top of their rumps, whereas the plains zebras do not. In the southern African population of plains zebra there are usually brown “shadow stripes” on the rump area i.e. on the rump the stripes follow a black, white, brown, white, black… pattern. Mountain zebras only have black and white stripes.

The Grevy’s zebra, compared with other zebras, is taller, has larger ears, and its stripes are narrower. The stripes of the Grevy’s zebra, like the mountain zebra, do not extend onto the belly and are black and white.
One of the most noticeable things about zebras are the black and white stripes, which do not seemingly blend into the environment. Guests often asks why the zebras have this coloration and patterning and this is not an easy question to answer. In fact, most researchers and biologists cannot give a definite answer to this question. Some of the theories of why stripes evolved in zebras are the following:

  • Zebras find the stripe patterning attractive and are easily able to identify other zebras from the stripe patterns. The stripe-pattern of a zebra is individual to that zebra (very much like a fingerprint) and can be used to identify specific animals. It is thought that a mother zebra will position herself between her newborn foal and the rest of the herd so that the foal can imprint on her pattern.
  • The stripes of a zebra form disruptive patterning, which breaks the outline of the animal. This can be used to deter predators, particularly when the zebras band together when chased by lions. In this case, with all the stripes blending with those of the other zebras who are close by, it could be difficult for a lion to separate each individual from the mass, causing it to be more difficult to visually isolate one zebra in order to leap on it.
  • There is a theory that the stripes could have a cooling effect on the zebras. Black colouration tends to attract heat, whereas white reflects heat and light. The juxtaposition of the stripes is thought to cause air movement around the zebra, which could help to cool the zebra down.
  • It is thought that the stripe patterns confuse the compound eyes of biting flies, such as tsetse fly, and studies have shown that flies do not like to land on stripy surfaces.
  • Since zebras are usually found in grasslands where heat-mirages and heat-hazes often occur, it is thought that the stripe-patterns of zebras tend to cause them to become almost invisible at a distance.

Another interesting titbit of information about the stripes is that although most people tend to think that zebras are white animals with black stripes (since some zebras have white underbellies) embryological evidence shows that the animal’s background colour is black and the white stripes and white bellies are additions.

The social system of plains zebras is very interesting and reads like a bit of a soap opera. Zebras are gregarious animals and live in small family groups, or harems, consisting of one stallion and his mares (sometimes up to six mares). Male zebras are slightly larger than females, weighing up to 350 kg and can be identified by their much thicker necks and a thin black stripe between the buttocks (the females have a thicker black stripe under the tail). In the wild, zebras usually live to be between 20 to 30 years old, although they can get up to 40 years in captivity.

When resources are good in a particular area different family groups may join up with other family groups and are then referred to as a “dazzle of zebras”. Even within the dazzles one can easily differentiate between each of the various family groups, who tend to stick together. In each harem the lead mare generally leads the family and decides where they go (although the stallion may direct her if he decides that they need to go elsewhere). The stallion usually follows on behind the harem and protects them from predator attacks (a good kick from a zebra could possibly break the jaw or other bones of an attacking lion), or advances and attentions of other male zebras. Bachelor males either live alone or with groups of other bachelors until they are old enough to challenge a breeding stallion and elope with one of his fillies. These fights can be quite vicious and involve a lot of rearing, kicking and biting. Zebras have powerful jaws and sharp incisor teeth and the results of bites can be seen on the numerous male zebras that have no tails anymore.

It is not an easy task to steal a young filly away and it can thus take a young male quite a while to build up his own harem. If, for some or other reason, another male does get to mate with one of the stallion’s mares and gets her pregnant the stallion will often kill the foal after birth by biting and kicking it. Studies in captivity have shown that mares who are impregnated by other stallions and then returned to the original stallion’s harem may self-abort the embryo, rather than give birth and have the foal killed by the resident stallion.

Female zebras mature earlier than the males, and a mare may have her first foal by the age of three. Males are not able to breed until the age of five or six. Mares may give birth to one foal every twelve months. She nurses the foal for up to a year. Like horses, zebras are able to stand, walk and suckle shortly (often within twenty minutes) after they are born. The stripes of a zebra foal are often brown and white instead of black and white and the black gets darker as they age. The coat of young foals is often fluffier than that of the adults.

Zebras do not have territories and will wander long distances to find good grazing or water. In East-Africa they may join up with the great wildebeest migration. Plains zebra tend to integrate well with other grazers, and can often be seen coexisting peacefully with other animals such as wildebeest, kudu, and impala, while some birds, such as the red-billed oxpecker, often eat the ticks and insects off the hides of zebras.

Zebras communicate with each other with high-pitched barks, whinnying and body language. A zebra’s ears signify its mood. When a zebra is in a calm, tense or friendly mood, its ears stand erect. When it is frightened, its ears are pushed forward. When angry, the ears are pulled backward. When surveying an area for predators, zebras will stand in an alert posture with ears erect, head held high, and staring. When tense, they will also snort. When a predator is spotted or sensed, a zebra will bark loudly, stare at the predator and then run away. They do not usually hide.

Zebras mainly feed on grass and their stomachs always look full. This is not necessarily the case, and the stomach is rounded or bloated because it is filled with gas. Zebras are known as hind-gut fermenters. This digestive system allows them to subsist on diets of lower nutritional quality than that necessary for other herbivores. In hind-gut fermenters the stomach has a single chamber which is connected to an organ called the caecum. This organ is found between the two intestines and is filled with a digestive fluid which helps to break down the food and cellulose found in grass. This form of digestion tends to produce a lot of gas, which does not escape out of the mouth as is the case with ruminants. This is the reason that horses and zebras tend to pass wind a lot. Due to the stomach always looking fat it can be quite difficult to visually ascertain the health of the individual. One of the easier and simpler methods of figuring out whether a zebra is sick or healthy is to look at the mane. Healthy zebras tend to have erect manes, whereas those who are sick often have manes that droop.

Historically, attempts were made to train zebras for riding or carrying since they have better resistance than horses to African diseases. While occasionally successful, most of these attempts failed due to the zebra’s more unpredictable nature, their stubbornness and their tendency to panic under stress. It has also been said that they do not have strong backs for carrying loads.

It is always a pleasure to see these unique and interesting equids in their natural environment. Zebras are truly iconic African animals. One of those amazing creatures that represent savanna systems.