Britannica Sources used in this answer

How do spontaneous ovulation and reflex ovulation differ in mammals?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Detailed cross-sectional illustration of a human ovary showing the stages of follicle development, ovulation, and corpus luteum formation, with labeled structures including primordial, primary, secondary, and mature follicles, a ruptured follicle releasing an ovum, and corpus luteum and albicans. An inset at the bottom shows the ovary's location in the female reproductive system. — ovary The steps of ovulation, beginning with a dormant primordial follicle that grows and matures and is eventually released from the ovary into the fallopian tube.

In mammals, the primary difference between spontaneous and reflex ovulation lies in the stimulus required to trigger the release of ovulatory hormones from the pituitary gland.12

Spontaneous Ovulation: In most mammals, ovulation occurs cyclically as a result of the spontaneous, rhythmic release of ovulatory hormones. This process is often regulated by environmental factors, such as photoperiods (cycles of light and dark), which establish an intrinsic brain rhythm that dictates reproductive activity. Because of these environmental cues, spontaneous ovulation often occurs at a predictable time of day or night within a species.12
Reflex Ovulation: In reflex ovulators—which include some species of cats, rodents, weasels, shrews, and rabbits—the act of copulation is essential to trigger the release of ovulatory hormones. In these animals, mating substitutes for the environmental stimuli that drive the hormonal release in spontaneous ovulators.123

Both processes ultimately serve the same biological function: the release of a mature egg from the ovary to enable fertilization.4