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Trophic Level II - The Herbivores |
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Trophic Level II - The Herbivores |
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Equus quagga
Length: 217-246 cm (85-97")
Height: 127-140 cm (50-55")
Tail: 47-57 cm (19-22")
Weight: 175-250 kg (385-550 lb.) female, 220-322 kg (485-710 lb.) male
Status: Common in national reserves and parks.
Habitat: Common zebras are found on grasslands, savannas and in open woodlands.
Their habitat must include permanent water. They prefer areas where there is firm footing
and will move off floodplains during the rainy season.
Food: Zebras eat grass. They are grazers. On short grass plains they will mow the lawn almost down to the roots. They will also eat the flower heads of taller grasses. Zebras are capable of feeding on a wide variety of grasses.
In the Serengeti-Mara, zebras are often seen with wildebeest. The grass species here are more suited to wildebeest than zebra, but across Africa, zebra are the more widely distributed species. Zebras can digest coarser grasses more readily than wildebeest and they can exist with poorer quality food (see Hindgut Fermenters and Ruminants). They are also more comfortable in the woodlands than wildebeest.
Zebras are the first to enter tall or wet pastures. Wildebeest follow after the zebras have trampled down the grass. They are, in turn, followed by gazelles. Gazelles are able to feed on the shorter shoots left behind by the other two species. (This is an example of rotational grazing. This practice has evolved in nature so that several different species can graze in the same pasture. Each species utilizes a different part of the food resource available.)
Social System: Common zebra stallions gather a harem of mares.
The mares are very loyal to the male and will stay with him until he or they die.
A young, mature stallion begins a harem by courting a young estrus mare. She will move away from her mother and father's group and this behavior attracts the attention of unattached males. There may be as many as 15 males courting her. Her father will try to herd her back into the harem and will inevitably meet up with the suitors. A fight usually ensues. Suitors must fight each other to determine who is the most fit.
The winner(s) must also fight the filly's father. The intruder is not out to defeat the harem master. This fight is one that allows the mare's father to assess the strength and vigor of the bachelor. If the suitor holds his own, the harem master will allow his daughter to join him and a new harem has begun.
It may be a year until she is finally bred and for five days of every month when she is in estrus her stallion must fight off rival males. She may actually "belong" to several different males during this period. Once she has a foal, she stays with the foal’s father. Should another stallion intrude, the harem stallion will be assisted in chasing him away by the other mares.
Harem Life
Eventually, a stallion will have anywhere from two to six females in his harem. These other females are taken from their father's herd in the same way. The females organize themselves into a strict dominance order. Each one knows its place and when the herd moves, they follow along in a line that seldom changes its order. The first mare and foal comes first. The second is second in line and so on.
The stallion is free to move wherever he wants.
When danger threatens, he will linger behind the mares and foals. 
He
will try to protect them as they make their escape. When a female is separated, he calls
to her and becomes very agitated in his behavior,
running back and forth and braying until she is once again safe with him.
If a herd member is injured or sick, the entire group will adjust their pace to accommodate the hurt animal.
Male offspring, called colts, are allowed to stay with their father's harem and are not chased away. They leave on their own when they are two or three years old to join a bachelor herd. These herds consist of young males and are led by the oldest among them. Rank order is based solely on age.
Daughters leave when they have a mate. Daughters will move with their stallions some distance from their mother’s harem-group. Such long distance moves by daughters are rare among the region’s grazers. Among these other species, the female calves usually remain in or near their mother’s herd. Scientists believe that the reason zebra mares move far away has to do with the lengthy period of time the male remains with his harem. By moving away from her father’s harem she helps ensure that he will not mate with his future granddaughters. This is not a problem for antelope because males maintain breeding rights for only a short period of time.
Unless the male is hurt, sick or killed, he will likely have his harem for up to 15
years.
Behavior: During her first courting stage with a new stallion, the young female displays behaviors that make it obvious to other males that she is in estrus. This attracts them to her and her stallion must constantly defend his breeding rights. If he is successful and she is bred by him, her future estrus periods are kept discreetly quiet. Only he knows when she is in breeding condition because he is constantly around her.
Zebras give birth all year round although there are seasonal peaks. In East Africa, most are born in December and January. This is also when most mating takes place. A newborn weighs between 31 and 35 kilograms (68-77 lb.). They stand within 15 minutes and will nurse within the hour.
The foal will imprint on the first zebra it sees and the mother will keep all other zebras away including last year’s foal. This will go on for several days until the mare is confident her baby recognizes her distinctive pattern. She then takes it into the herd. Among the grazers, the zebra mother is unique. When a foal lies down to sleep its mother will stand patiently over it, nose down, until it awakes. Cow wildebeest and other antelope will graze and wander away from their resting calves.
The reaction of zebras to danger is quite different from that of wildebeest. When an enemy is spotted, the zebra form a semicircle, facing the hunter. They stare, with heads raised and ears pointed forward. Other zebras notice this and turn to face the threat. They may even move towards the danger.
Zebras like to keep a distance of about 100 meters (100 yards) from danger. This is their flight distance. Any closer and the predator might be able to make a dash and grab one of them.
Anti-predator Adaptations
Should a predator close on the fleeing
herd, the stallion will bite and kick at it. 
Zebras are fighters and have been known to fight off attacks
by crocodiles, spotted hyenas and wild dogs.
Despite their defense, zebras are a favorite prey of lions and spotted hyenas and many fall victim. Most hunts take place at night when the advantage lies with the predator. Zebras will seek an open area to spend the dark hours but lions are adept at exploiting even the smallest amount of cover. Foals are especially vulnerable. An attack in darkness will spook the herd and in the panic, the babies are often separated from their parents. They are then easy victims.
Hyenas can chase a herd for long distances and if they can isolate a mare or foal there may be little a stallion can do to save her.
Several years ago in the Serengeti, a pack of wild dogs learned to hunt zebras. They would chase the harem and separate a likely victim. One would grab its tail and another its upper lip. This effectively pinned the zebra so that other members could kill it. There was only one pack that did this on a regular basis and when the pack contracted a disease and died out, the behavior died with them.
The zebra migration is one of the Serengeti-Mara ecosystem spectacular sights. Thousands of zebra groups join together and form huge herds numbering in the tens of thousands. These big herds are usually found moving to and from good grazing. When they reach a feeding spot and are relaxed, the many harems are easily identified. They form small groups that dot the plains.
The common zebra is not territorial. Each harem group uses a home range that overlaps that of several other groups. In the Serengeti, territories range in size from 260 to almost 400 square kilometers (100-154 square miles) in the wet season on the plains. In the dry season, the size of a territory increases and may be up to 650 square kilometers (1430 square miles) in the woodlands. Migration routes between one location and the other can be 100 to 160 kilometers long (62-100 miles).
Zebra territories in the richer environment of Ngorongoro Crater are much smaller. Zebras there uses ranges between 75 and 260 square kilometers (29-100 square miles).
A Zebra’s Stripes
Why does the zebra have stripes? Several possible explanations have been put forth. One holds that the stripes confuse a predator when it is chasing them. Another suggests that the stripes are good camouflage, although anyone who has ever been on the plains of Africa knows that zebras are by far the easiest of the plain’s game to spot. Another suggests that the alternate black and white striping helps maintain a constant heat.
Perhaps closest to the truth are these two possibilities:
In order to have sharply defined stripes, an animal’s coat must be short. Wild horses that are found in the far north have shaggy coats that are too long for stripes. Their coats are solid colors. None have stripes. By this same logic one would predict that the finest striping would be found on zebras that live in the warmest climates where a short coat would be an advantage. The zebras found in the Serengeti-Mara do exhibit much clearer, finer stripes than those found further south.
Predators: Lions and
spotted hyenas are the main predators on all
classes of zebra; young, adult and aged. Wild dogs will take foals. Leopards will also
take foals when the herds are in the woodlands. 
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CDROM Index | Title Page | Contents | Index | Glossary | Bibliography | Appendices | LifeStories Online
Dave Taylor's African Safari - Book 3: Trophic
Level II - The Herbivores (Standard
Version)
Copyright © 1999 Dave Taylor & James Cash