Extrous

Extrous refers to a period of sexual receptivity in female mammals. This phase, also known as estrus or "heat," is a specific part of the reproductive cycle during which a female is fertile and willing to mate with a male. The duration and signs of estrus vary significantly across different species.

The onset of estrus is typically triggered by hormonal changes, primarily involving estrogen and luteinizing hormone (LH). These hormones prepare the female's reproductive tract for potential pregnancy and influence her behavior, making her more attractive and receptive to males. Common behavioral signs can include restlessness, increased vocalization, mounting behavior, and seeking out males. Physical signs may involve swelling or changes in the appearance of the external genitalia.

Following estrus, if mating does not occur or fertilization is unsuccessful, the female will typically enter a period of anestrus, during which she is not sexually receptive. The reproductive cycle, including estrus, can be influenced by factors such as season, age, nutrition, and social cues. Understanding estrus is crucial in animal husbandry and wildlife management for breeding programs and population control.