zebra

Plains Zebra | Equus quagga

Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Equidae
Species:	Equus quagga

facts

Shoulder Height:	1,35 m
Tail Length:	0,46 – 0,56 m
Mass:	227 – 325 kg
Teeth:	36 - 42
Speed:	60 km/h
Gestation:	365 days
Litter size:	1
Breeding Season:	Breed throughout the year
(Peak):	August / September
Life span:	35 years

Zebras possess good eyesight. They have a high-pitched bark, neigh and squeal. They can weigh up to 325 kilograms and a shoulder height of 1,35 meters. Zebras are frequently preyed upon by lion. Water dependent, they will travel many kilometres when this is lacking and when necessary will dig for water. Highly sociable, zebra herds may number from five to thirty and are often associated with blue wildebeest.

There are three species of zebras: the plains zebra, the Grévy's zebra and the mountain zebra. The plains zebra and the mountain zebra belong to the subgenus Hippotigris, but Grevy's zebra is the sole species of subgenus Dolichohippus. The latter resembles an ass, to which it is closely related, while the former two are more horse-like. All three belong to the genus Equus, along with other living equids.

Zebra prefer shorter, green grass such as that which flushes after a fire or the first rains but they do also graze upon tall, coarse growth.  Taller grass is cropped and made more suitable for the foraging habits of blue wildebeest and other antelope in a process known as grassland succession.

Wildebeest prefer very short grass and are often found in association with zebra for this reason and to benefit from their excellent vigilance.

Even though zebra are strictly grazers, they have been known to browse occasionally, most probably at the hardest time of the year when there is little else available.  They also dig up the rhizomes (underground stems) of grasses that are often more succulent than the above ground parts, particularly in winter.

Zebra are hind-gut fermenters.  Lacking the four-chambered stomach of a ruminant, zebra pile all their often fibrous food into one gut which digests via fermentation.  The breakdown of cellulose is less effective than with a ruminant but they can digest larger amounts of food faster.

Large quantities of gas are released as a by-product and this inflates their bellies so that they always look fat and healthy.  It is also the cause of the flatulence experienced when zebra take fright and run away.

Zebra are unselective bulk feeders.  Eating a lot of fibre means that they require a regular supply of water to facilitate digestion.  Zebra must drink daily and are seldom further than 10 km from water.

They are fussy drinkers preferring clean water and in this regard they may scrape a hole next to a waterhole and allow clean water to filter through before they drink or they may carefully skim cleaner water off the surface.

Zebra do not have territories, instead, the defended resource of a stallion in his four to six mares and their foals.  A stallion practises a true harem system (one male with a number of females), which is bought at an incredible price.

Colts leave the natal herd of their own accord at 2 years of age but between 4.5 and 12 years of age, they will approach other herds with the intention of abducting fillies, one by one, to form their own harems. 

This is no easy feat as each existing harem is defended valiantly by the stallion, which will not let the young bachelor merely lure his fillies away – through a protracted period of sometimes a year, he is forced to prove himself.

Often this is done through vicious fighting between the contender and the filly’s father as well as other suitors.  If the young stallion can get it right to mount and impregnate a filly during her annual five day oestrus period the filly will become his and she will remain faithful to him. 

He will then pursue another.  This protracted courtship ensures that only the fittest stallions prevail.

Amongst the mares there is a strict rank hierarchy, which is linked to age abut initially also to the “first wife, second wife” arrangement.  Whichever filly was abducted first, becomes the dominant mare.  The groups bond through allo-grooming (mutual grooming).

Males practise flehmen to check the reproductive status of the mares.  This is the process whereby liquid or air-borne chemicals from the mare’s urine are pumped into an organ on the roof of the mouth known as the organ of Jacobson or vomeronasal organ.

A facial grimace whereby the upper lip is pulled back, relaxes the opening of the glands allowing the chemicals to enter.  The hormonal content of the urine is thus evaluated and the stallion consequently determines whether a mare is ready to mate or not.

The foal of a zebra is remarkably precocial, standing on its own after just 10 minutes of its birth.  It can walk within 30 minutes and runs within the hour.  The protracted year-long gestation ensures the foal is born well developed since it must be able to run to escape danger almost immediately in order to survive.

Depending on nutritional value of available forage, foals will suckle for almost a year.  During weaning, they consume some adult dung to get micro-fauna to aid their own digestion.

The Burchell’s zebra has characteristic “shadow stripes” between the black and white stripes of the rump which gives the body a dirty chestnut colour.

Each zebra has a unique stripe pattern.  When young zebra are born, the mare will screen her foal from any other zebra until her own stripe pattern has imprinted on the youngster, ensuring recognition.

One theory regarding why zebra have stripes suggests that the confusion caused by a group of zebra fleeing simultaneously creates a screen for the individuals’ escape.  The blur of black and white supposedly makes it difficult for predators to separate out an individual target.

The weaker, older or slower members of the group may lag behind and generally it is the isolated members of the population that are picked off by predators first.  Zebra are however group-orientated animals and will attempt to rally around their weaker individuals during times of threat.

There is also a greater concentration of capillaries below the black stripes than the white stripes, the function of which is thought to be an aid in dissipating heat.

The black stripes get hotter than the white, resulting in a lower pressure above these stripes than the white, resulting in a lower pressure above these stripes than the white.  The pressure gradient causes cooler air to flow from the white stripes to the black stripes.

These “breezes” help to cool the blood and to dissipate heat from the black stripes.  A big negative of stripes is that they are more attractive to flies for some reason. 

Although they have good eyesight, it is not better than that of humans during the day.  Although Zebras lack in human colour vision, their night sight is better than ours owing to the higher concentration of rod cells in the retina.

Smell plays an important role; the mother and foal recognise each other by body scent, thus forming the initial parent/ offspring bond. Flehmen is well developed with a very pronounced lip-curl.

The ears are relatively small compared to those of many other herbivores, possibly indicating that sight and maybe even smell, are more important for survival and social well-being in the open habitat they prefer.

Modern man has had great impact on the zebra population. Zebras were, and still are, hunted for their skins, and for meat. They also compete with livestock for forage, and sometimes culled.

The Cape mountain zebra was hunted to near extinction, with less than 100 individuals by the 1930s. The population has increased to about 700 due to conservation efforts and even though both mountain zebra subspecies are currently protected in national parks, they are still endangered.

The Grevy's zebra is also endangered. Hunting and competition from livestock have greatly decreased their population. Because of the population's small size, environmental hazards, such as drought, are capable of affecting the entire species. Plains zebras are much more numerous and have a healthy population. Nevertheless, they too have been reduced by hunting and loss of habitat to farming. One subspecies, the quagga, is now extinct.

Zebras are often seen nodding their heads and curling their lips and this is most probably due to parasitism by a type of fly called a botfly.  Dependent upon the species, these flies lay their eggs around the nasal or oral cavities or around the eyes.

The eggs hatch to reveal maggots that immediately start to feed on the membranes in these areas.  With regard to those that move up the nostrils, the feeding activity becomes very irritable and the zebra (or other host species) tries to get rid of the nuisance by either nodding the head or snorting (this is rare and is more common in mammals such as wildebeest). 
This hopefully results in the maggots becoming dislodged and being dropped to the ground where they pupate into flies within the soil.  The lip curling up in conjunction with the head being nodded is simply a local reflex response to the irritation in that area.

How the Zebra got his Stripes
A Zulu story

One day long ago, a very big, very fierce baboon came down from the trees to live on the banks of the great Umfolozi river. 

Here he made his home and declared to all the other animals that the land all around belonged to him and they were not to use the water in the river. He alone was to be allowed to drink.

There was one among the animals who decided to stand up to fearful Baboon. This was a proud young zebra stallion, Dube.

In those days, zebras were pure white, like the fabled unicorn. Dube was brave and he challenged Baboon to a fight. Baboon, a fierce veteran of many battles, agreed. He knew all about fighting.

“The loser of the fight,” he said, “will be banished forever to the barren kopje across the river.” And he told the zebra to come to his kraal the next morning. The fight was long and terrible. Both animals fought with all their strength, using the weapons the Creator had given them. Dube used his sharp hooves and teeth. Baboon used his long fangs and his agility.
Eventually, Baboon gained the upper hand and poor Dube was thrown backwards into the blazing logs of the kraal fire. The cruel flames licked all over his body, searing his fine white coat. The dreadful pain gave Dube a surge of new strength and with a mighty kick he sent Baboon flying.

Over the river sailed Baboon, right onto the rocks of the kopje on the other side. Baboon landed with such force that a bald patch remains on his behind to this day.

But Dube too was marked for life. The burns form the blazing logs in Baboon’s fire left black stripes all over his snow-white coat. But at least he had won and from that day on, the water was free to all the animals.

Since then, zebras wear their stripes with pride and while baboons are banished to stony kopjes, the zebras dwell on the open plains, coming and going to the river just as they please.