The estrous cycle is a natural reproductive cycle in female mammals, characterized by a series of hormonal changes that prepare the body for potential pregnancy. It typically includes several stages: proestrus, estrus, metestrus, and diestrus. During the estrus phase, females are receptive to mating, which is often referred to as being "in heat." The length and characteristics of the estrous cycle can vary significantly among species. For example, in dogs, the cycle lasts about six months, while in cows, it occurs approximately every 21 days. Understanding the estrous cycle is essential for effective breeding and animal management practices.