Grant’s zebra is a subspecies of the plains zebra, and rangers aver the dry grasslands of east Africa from Zambia to Ethiopia. It is one of the best-documented species, thanks mainly to the work of Hans Klingel who made a close study of over five 500 specimens over a number of years.
In general, Grant’s zebras live in family groups that consist of a male (stallion), a harem of females (mares) and their young foals. Young stallions remain with the group until they are four years old, when they leave to form bachelor herds. They are not chased off, but leave of their own accord, and the head stallion will often go in search of them if they wander away from the family group prematurely. Young mares will stay with the group for longer, and may even mate with the dominant stallion to produce zebra foals of their own.
By the age of five or six, a stallion is ready to leave his bachelor herd and collect a harem. Inevitably there is intense competition for mares in breeding condition, and even when the harem has to be on constant guard against other stallions who try to lure mares away. He helped somewhat by the fact that the mares do not all come into season at the same time, so he does not have to guard them all.
Occasionally an intruder will fight with the dominant stallion is busy elsewhere, will often suffice. In some cases the head stallion of a large herd may not be in full control, and another male may come to share his position. Eventually the younger animal will oust his senior altogether, often without a struggle. Old stallions invariably lose control of their harems at some stage, and go off to join bachelor herds.
This type of social organization means that young males who have left their mothers cannot occupy permanent position in the hierarchy until they have gathered their own harem. The dominant position in each herd is always occupied by a stallion, but despite this, he does not generally lead the herd as they travel between grazing sites.
This role is usually carried out by a senior mare. The other mares recognize a strict subordinate hierarchy that is maintained at all times, and which is evident whenever the herds is on the move. Each mare travels with her foals, which are accorded honorary rank immediately below that of their mother and can share in her advantages. These may include being near the front of the queue at the waterhole, or gaining access to better grazing.
The group is very close-knit, and one result of this is that young foals will attach themselves to other mares if they get the chance. To prevent this, each mare tries to stay apart from the rest of ‘imprinted’ in her foal’s memory. They will not allow other mares to approach their offspring during this critical period. As with all the horse family, the pregnancy is long-and only one foal is born at a time.