Estrus is a recurring period in the reproductive cycle of many female mammals, during which they are fertile and receptive to mating. This phase is often referred to as "heat" and is characterized by specific behavioral and physiological changes, such as increased vocalization, restlessness, and a heightened interest in males. During estrus, the ovaries release eggs, and hormonal changes prepare the body for potential pregnancy. The length and frequency of estrus can vary significantly among species, with some animals experiencing it seasonally, while others may have multiple cycles throughout the year.