What term describes the stage when an animal is not within an estrus cycle?

The term "anestrus" refers to the stage of the reproductive cycle in animals when they are not experiencing any signs of heat or estrus behavior. During anestrus, the body is in a resting phase, and there is no ovarian activity taking place. This period can vary in length depending on the species and individual factors, such as age and health, but it is essentially a time when the reproductive system is inactive.

Proestrus, metestrus, and estrus are all active reproductive phases. In proestrus, the follicles in the ovaries begin to mature, which prepares the body for the possibility of mating. Estrus, or heat, is the stage where the female is receptive to mating. Metestrus follows estrus and involves the changes that occur after the female has been in heat, which includes hormonal changes and preparation for potential pregnancy. Since anestrus is defined specifically as the absence of these activities, it clearly distinguishes itself from the other phases of the estrous cycle where reproductive processes are actively occurring.