When sexually mature, stallions leave their birth group to start their own breeding group. Fully mature mares leave their breeding group by the invitation of a nonrelated mare. All zebras in a breeding group are nonrelated. Mountain and plains stallions establish their breeding groups by collecting four to five females to form his harem. Stallions from these two zebra species are aggressively territorial towards other males. Some Grevy's zebra stallions aren't territorial and travel in breeding groups of two to six stallions or foals. Breeding groups migrate constantly in search for adequate food and water.
Mating season varies between each zebra species. Grevy's and common zebras strictly mate from August through October, while mountain zebras breed throughout the year, although the peak season is December to February. Adult stallions mate with all the mares in his breeding group. Mares are usually two to three years old when they're ready to mate; stallions are four to five years old when they're fully mature. After mating, the gestation period of zebras usually lasts 11 to 13 months. Zebra mares are only able to produce one foal per year.
When foals are born, they're able to walk within 20 minutes of birth. After an hour of their birth, young foals can run with the group. Mares usually nurse their foals for approximately eight to 13 months. Also, mares don't allow other members of the group to approach the foal until she and her offspring imprint one another--the act of the foal recognizing the mare as its mother. After 13 months pass, mares wean foals from nursing so that their offspring can find food on their own. Foals leave their group once they've reached full maturity.
The mating and reproduction process is the same for zebras in zoological park captivity as it is in the wild. In captivity, though, zookeepers keep young zebras in climate-controlled areas during the winter. Also, zoos use the stallions to mate with mares from other zoos. Most animals species don't breed in captivity. However, zebra breeding occurs through the Species Survival Plan, a program operated by the Association for Zoos and Aquariums, or AZA. Zebras qualify for this program due to their endangerment in the wild. The Grevy's zebra is endangered, according to the International Union for Conservation of Nature. Mountain zebras have a Vulnerable status.