Plains Zebra (Equus burchelli)
Social System
The social organization of the Plains Zebra is divided into two groups: harem and bachelor. Bachelor groups average three males without a dominance hierarchy. The harem group is made up of unrelated individuals and averages seven members with strong personal bonds existing among members. The alpha male is the most dominant member then descending to the newest acquired female at the bottom of the hierarchy. Mutual grooming among members helps strengthen the bonds in the group (Moss, 1982). The most dominant female, generally the oldest, leads the family to different areas to graze and obtain water (Ciszek, 1996). Males without a harem group live in bachelor herds or in solitary, although very infrequently (Klingel, 1969). The harem is the only group to have a dominance hierarchy, as there is no evidence of a dominance hierarchy among stallions. Stallions will fight when one comes too close to the harem of another. The harem is a strong motivating factor in an aggressive encounter and a stallion will generally win a fight when his harem is in jeopardy (Schilder, 1988)
The zebras in a harem group recognize one another by voice, stripe pattern, and scent. The members of this group remain together for years and when the stallion is replaced by another due to old age or sickness the females remain together in their original group (Klingel, 1969)
pictures courtesy of Darren New
More Information
| The permanent harem society benefits the Plains Zebra because the male defends the females while they obtain the nutrients they require through grazing. The reproductive success of the female depends on long periods of interrupted grazing. The stallion defends the female from advances of other males, which normally would interrupt her grazing. The stallion is also guaranteed reproductive success (Rubenstein, 1993). The female zebra must travel a fair amount to acquire all the resources needed, making it more beneficial for a stallion to defend a group of females rather than a territory to attract females (Hack & Rubenstein, 1998). |
Comments/Questions?