page_title: Equus (genus)
section_title: Reproduction and parenting
hierarchical_section_title: Equus (genus) / Biology / Reproduction and parenting
caption_attribution_description: English: Grevy's Zebra
context_page_description: Equus is a genus of mammals in the family Equidae, which includes horses, donkeys, and zebras. Within Equidae, Equus is the only recognized extant genus, comprising seven living species. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. The genus most likely originated in North America and spread quickly to the Old World. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes, and long tails. All species are herbivorous, and mostly grazers, with simpler digestive systems than ruminants but able to subsist on lower-quality vegetation.
  While the domestic horse and donkey exist worldwide, wild equine populations are limited to Africa and Asia. Wild equine social systems are in two forms; a harem system with tight-knit groups consisting of one adult male or stallion, several females or mares, and their young or foals; and a territorial system where males establish territories with resources that attract females, which associate very fluidly. In both systems, females take care of their offspring, but males may play a role as well. Equines communicate with each other both visually and vocally.
context_section_description: Among harem-holding species, the adult females mate only with their harem stallion, while in other species, mating is more promiscuous and the males have larger testes for sperm competition. Estrus in female equines lasts 5–10 days; physical signs include frequent urination, flowing muscus, and swollen, everted labia. In addition, estrous females will stand with their hind legs spread and raise their tails when in the presence of a male. Males assess the female's reproductive state with the flehmen response and the female will solicit mating by backing in. Length of gestation varies by species; it is roughly 11–13 months, and most mares come into estrus again within a few days after foaling, depending on conditions. Usually, only a single foal is born, which is capable of running within an hour. Within a few weeks, foals attempt to graze, but may continue to nurse for 8–13 months. Species in arid habitats, like Grévy's zebra, have longer nursing intervals and do not drink water until they are three months old.
  Among harem-holding species, foals are cared for mostly by their mothers, but if threatened by predators, the entire group works together to protect all the young. The group forms a protective front with the foals in the center and the stallion will rush at predators that come too close. In territory-holding species, mothers may gather into small groups and leave their young in "kindergartens" under the guard of a territorial male while searching for water. Grévy's zebra stallions may look after a foal in his territory to ensure that the mother stays, though it may not be his.
caption: Grévy's zebra foal
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