(1) Women's sexuality is not limited to a specific period of estrus , as it is in almost all other mammals.(2) The number of males and the number of females in estrus within a 10-mile radius of the male was recorded at each location.(3) A beef cow has a 21-day estrous cycle, the period from one estrus , or heat, to the next.(4) Females breed when they are in estrus - a brief period of ovulation that only occurs every two years and lasts just a few days.(5) In adult females, social rank modulates the length of behavioral estrus , with high ranked females mating for longer periods of time prior to ovulation than lowed rank females.(6) However, it is also possible that in years of late snow-melt, pikas may lose litters or reabsorb litters and then breed again in post-partum estrus .(7) Two trials in Texas demonstrated a dramatic drop in pregnancy rates for females displaying estrus during June through September compared with earlier months.(8) a mare in estrus(9) However, existing evidence suggests that family breakups, onset of estrus , and breeding opportunities are linked.(10) Around 18 hours after giving birth, females experience postpartum estrus , and mate again.(11) Fillies began ovulating and advertising estrus by adopting a distinctive posture between one and two years of age.(12) The estrous cycle is 28 days with a 3 day period of estrus .(13) A female may come into her brief period of estrus at any time during the mating season, which runs from late November through mid-January.(14) u2018When the female is in estrus , breeding bulls that are 35 to 55 years old and in their prime can be many miles away,u2019 Garstang said.(15) After producing a foal, her periods of estrus are more difficult to detect, and she remains with the father of her offspring.(16) Therefore, if high population density results in increased contact between individuals, this may stimulate ovarian activity and synchronize estrus between females.