Estrous, << EHS truhs, >> cycle is the process that prepares the females of most species of mammals for mating and bearing young. It is also called the breeding cycle. Among many mammals, the estrous cycle occurs during a certain period, called the breeding season. The cycle is timed so that the young are born at the time of year when they have the best chance of survival.
During the estrous cycle, a period called estrus, or heat, occurs. The female is sexually excited throughout estrus and, among most species of mammals, will mate only during this period. The length of both the estrous cycle and estrus varies among the species. In most rats, the cycle lasts about 4 days, and estrus lasts about 14 hours. Among most breeds of dogs, the cycle lasts about six months and estrus lasts about three weeks.
Some mammals, including human beings and most apes, do not have such an estrous cycle. The females of these species have a menstrual cycle, which prepares them to bear young (see Menstruation).
