What Is an Estrus Cycle?


Quick Answer

The estrus cycle is the sexual cycle in female mammals during which they are in heat and ready to mate. The estrus cycle has been observed in all mammals, except the higher primates, and some animals are capable of having multiple estrus cycles during the course of their breeding season, states the Encyclopaedia Britannica.

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Full Answer

The estrus cycle consists of four stages: the proestrus, estrus, metestrus and diestrus. During the first stage, the corpus luteum regresses, progesterone declines and the preovulatory follicle undergoes its final growth phase. Ovulation usually occurs during estrus, although some animals, such as cows, ovulate during the metestrus stage. Corpora lutea begin to develop during the metestrus stage, and they begin to function properly during the diestrus stage. The proestrus and estrus stages make up the follicular phase, and the metestrus and diestrus stages make up the luteal phase, states the University of Wyoming.

The interval between estrus cycles varies greatly between animals, and animals with long periods between estrus cycles, such as the elephant or rhino, are at greater risk of extinction, states the University of Wyoming. During the estrus cycle, many female mammals give off pheromones, allowing males to smell when they are in heat, states the Encyclopaedia Britannica.

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