*Rothstein, A., and J. G. Griswold (1991) “Age and Sex Preferences for Social Partners by Juvenile Bison Bulls.”
*Sinclair, A. R. E. (1977)
*Tulloch, D. G. (1979) “The Water Buffalo,
OTHER HOOFED MAMMALS
MOUNTAIN, PLAINS ZEBRAS
IDENTIFICATION: The familiar wild horse with a black-and-white-striped pattern; Mountain Zebras usually have a distinctive dewlap. DISTRIBUTION: Southern and eastern Africa; Mountain species is endangered. HABITAT: Mountainous slopes and plateaus; grassland, desert, semidesert. STUDY AREAS: Mountain Zebra National Park, South Africa, subspecies
TAKHI
IDENTIFICATION: The wild ancestor of domestic horses; coat usually tan or chestnut colored, with an erect mane, black tail and lower legs, white muzzle, and thin black stripe along back and several on upper forelegs. DISTRIBUTION: Formerly in central Asia (Mongolia, Kazakhstan, Sinkiang, Transbaikal); now extinct in the wild. HABITAT: Steppes. STUDY AREA: Bronx Zoo, New York.
Social Organization
Mountain and Plains Zebras have two main social units: breeding groups containing a herd stallion and three to five females with their offspring, and nonbreeding or “bachelor” groups. Groups combine to form herds numbering in the tens of thousands in Plains Zebras. Little is known of Takhi social organization in the wild, where the species is extinct (although it is beginning to be reintroduced from cap-418 tive populations). It is likely that they have a system similar to that of Mountain and Plains Zebras, including both bachelor and “harem” herds.
Description
Takhi mares occasionally mount each other; in some cases, pregnant females perform this sexual behavior with other females. Mares may mount each other from a sideways position in addition to from behind (the usual position for heterosexual mounting, although younger males also sometimes use a lateral mounting position). Such females may be among the highest-ranking mares in the herd and can also be noticeably aggressive toward males, kicking or biting them when the latter try to court other females.
Nonreproductive and Alternative Heterosexualities
As noted above, a large proportion of the male population in Zebras, as well as in Takhi, are nonbreeding bachelors. Some female Zebras also join the bachelor herds and do not participate in heterosexual activity while there (they remain for just under a year, on average). Wild equids also engage in an assortment of nonprocreative heterosexual activities. Males of all three species sometimes perform heterosexual mounts without an erection or penetration, while Takhi mares sometimes REVERSE mount stallions. Male Mountain Zebras and Takhi also frequently masturbate by erecting the penis and flipping it against the belly. Female equids sometimes also engage in an activity known as CLITORAL WINKING as part of courtship, in which the clitoris is rhythmically erected and wetted against the labia (often in conjunction with urination). Mountain Zebras occasionally participate in incestuous copulations: both father-daughter and brother-sister matings have been documented, although generally such pairings are avoided because females leave their family’s herd before they reach sexual maturity. In addition, male Plains Zebras often try to mate with unrelated juvenile females that are not yet sexually mature. In fact, stallions—alone or in groups of up to 18 at a time—may “abduct” adolescent females by separating and chasing them from their family groups, after which they will try to copulate with the young mares. Interestingly, the female shows the behavioral signs of being “in heat” before she reaches the age when she can actually conceive; usually an “abducted” mare returns to her family group after her period of “heat” is finished. In contrast, in Takhi it is often the females who behave aggressively toward males (as mentioned above).
In these equids, a number of violent behaviors are also directed toward young foals. Mountain Zebra and Takhi stallions occasionally kill foals; in the latter species, infanticide occurs when the male grabs the youngster by its neck, shaking it and tossing it into the air. Female Mountain Zebras also sometimes accidentally kill their foals by kicking them; ironically, this may occur when they are trying to defend them from other mares, who are often aggressive toward unrelated foals. However, in a few cases females have adopted an unrelated foal, and in one instance a female even rejected her own offspring and adopted another. A Plains Zebra mare may also allow another mare’s foal to suckle from her. Although Takhi males are not as involved in parenting as mares, a stallion may act as a “surrogate mother” to his own foal if it has lost its mother, even allowing the foal to “suckle” on his penis sheath.