Editing Plains zebra (section)

===Social structure===
[[File:Zebra Botswana edit02.jpg|thumb|A zebra harem within a herd]]
The plains zebra is highly social and usually forms small family groups called [[Harem (zoology)|harem]]s, which consist of a single stallion, several mares and their recent offspring. The adult membership of a harem is highly stable, typically remaining together for months to years. Groups of all-male "[[Bachelor herd|bachelors]]" also exist. These are stable groups of up to 15 males with an age-based hierarchy, led by a young male. These males stay in their groups until they are ready to start a harem. The bachelors prepare for their adult roles with play fights and greeting/challenge rituals, which take up most of their activities.<ref name="Estes 1991"/>

Multiple harems and bachelor groups come together to form larger herds of hundreds of animals, especially during migrations. Plains zebras are unusual among harem-holding species in forming these groups. In addition, pairs of harems may create temporarily stable subgroups within a herd, allowing individuals to interact with those outside their group. Among harem-holding species, this has only been observed in primates such as the [[gelada]] and the [[hamadryas baboon]].<ref name="Rubenstein and Hack 2004">{{cite book|author=Rubenstein, D. I.; Hack, M.|year=2004|contribution=Natural and sexual selection and the evolution of multi-level societies: insights from zebras with comparisons to primates|pages=266–279|title=Sexual Selection in Primates: New and Comparative Perspectives|editor=Kappeler, P.; van Schaik, C. P.|publisher=Cambridge University Press|isbn=978-0521537384}}</ref> Bachelor groups tend to be at the periphery of herds and when the herd moves, the bachelors trail behind.<ref name="Skinner"/>

Stallions form and expand their harems by abducting young mares from their natal harems.<ref name="Estes 1991"/> When a mare reaches sexual maturity and has her first [[oestrous]] cycle, she attracts the attention of nearby stallions, both bachelors and harem leaders. Her family stallion (likely her father) chases off or fights stallions attempting to abduct her. Even after a young mare is isolated from her natal harem, the fight over her continues until her oestrous cycle is over and it starts again with the next oestrous cycle. It is rare that the mare's original abductor keeps her for long.<ref name="Klingel 1969">{{cite journal | last1 = Klingel | first1 = H. | year = 1969 | title = Reproduction in the plains zebra ''Equus burchelli boehmi'': behaviour and ecological factors | journal = J. Reprod. Fertil. Suppl. | volume = 6 | pages = 339–345 }}</ref> When the mare finally [[Ovulation|ovulates]], the male that impregnates her keeps her for good. Thus, the mare becomes a permanent member of a new harem.<ref name="Klingel 1969"/><ref name="Adlen et al. 1995">{{cite book|author=Alden, P. C., Estes, R. D., Schlitter, D., McBride, B.|year=1995|title=National Audubon Society Field Guide to African Wildlife|publisher=Chanticleer Press, Inc|page=151|isbn=978-0679432340}}</ref> Oestrus in a female becomes less noticeable to outside males as she gets older, hence competition for older females is virtually nonexistent.<ref name="Grub 1981"/>

[[File:Fighting Burchell's Zebras in Addo National Elephant Park.JPG|thumb|left|Two male zebras fighting in the [[Addo Elephant National Park]], South Africa]]
Mares exist in a hierarchy, with the alpha female being the first to mate with the harem stallion and being the one to lead the group. When new mares are added to the group, they are met with hostility by the other mares. Thus, the harem stallion must shield the new mares until the aggression subsides.<ref name="Estes 1991"/><ref name="Adlen et al. 1995"/> The most recently added females rank lowest. Females that become unfit or weak may drop in their rank, though. The female membership of a harem stays intact, even if a new stallion takes over. During herd gatherings, family stallions may be cordial towards each other, while the mares are less tolerant.<ref name="Grub 1981"/>

A stallion defends his harem from other males. When challenged, the stallion issues a warning to the invader by rubbing nose or shoulder with him. If the warning is not heeded, a fight breaks out. Zebra fights often become very violent, with the animals biting at each other's necks, heads, or legs, wrestling to the ground and occasional kicking. Sometimes, a stallion lies still on the ground as if surrendering, but once the other male lets up, he strikes and continues the fight. Most fighting occurs over young mares in oestrus and as long as a harem stallion is healthy, he usually is not challenged. Only unhealthy stallions have their harems taken over and even then, the new stallion gradually takes over, pushing the old one out without a fight.<ref name="Estes 1991"/>