رفتار جنسی مادیان

The mare is seasonally polyestrus, having an anovulatory period during the short light days of late fall and early winter, and beginning to ovulate as the days become longer during the winter. The complete estrus cycle is typically about 3 weeks, with 5 to 7 days of estrus and approximately 2 weeks of diestrus. When a mare lives within the natural social structure of the horse, i.e. a family band with several adult mares and one or more stallions, estrus is characterized by repeatedly approaching the stallion, frequent urination, deviating the tail away from the perineum, and standing still with the hind limbs spread apart. Diestrus is characterized by avoidance of an approaching stallion, and aggression toward the stallion, such as squealing, striking, and kicking, if he persists in attempting to court the diestrus mare. However, mares and stallions with long-term social relationships will often rest together, graze together and groom each other, all without sexual interactions. Hormonally, estrous behavior in the mare is initiated by estradiol that is secreted by the follicle, while estrous behavior is suppressed by progesterone, secreted by the corpus luteum. Mares are unusual among the ungulates in that they periodically exhibit estrous behavior during the anovulatory period. This is probably due to the release of estrogenic steroids secreted by the adrenal cortex. The display of sexual behavior by the mare throughout the year is thought to facilitate maintenance of the horse's social structure, in which the male remains with a group of females year round, in contrast with most ungulates in which the females and males only come together during the mating season.

The sexual behavior of the mare has evolved in the social context of family groups that typically consist of multiple adult mares and their young offspring, plus one or more adult stallions. This long-term cohesive family structure is probably an important factor in the evolution of the unusually long period of estrus in the mare, i.e. 5–7 days versus 1–2 days for other female ungulates. The long period of estrus in all the mares of the herd would facilitate maintenance of proximity to the mares by the herd's stallion. While strong social bonds develop between the mares and the stallion(s), the social core of the group is formed by the mares, and it is not necessary for the stallion to be present for the mares to remain as a cohesive group. Nevertheless, the stability of a mare's consort relationship with a given stallion significantly correlates with her lifetime reproductive success (Kaseda et al., 1995). In the context of sexual interactions with the stallion, however, the mares may become very competitive, and if more than one mare is in estrus at one time, the higher ranking mare will actively disrupt interactions between the subordinate mare and the stallion and drive the subordinate away from proximity to the stallion (Asa et al., 1979).