Detailed Explanation of the Dog Estrus Cycle and Behavioral Signs

Normal dogs go into estrus twice a year, generally once in spring from March to May and once in autumn from September to November. When a female dog is in estrus, her body and behavior show characteristic signs. These mainly manifest in the following stages.

① Proestrus. This is the preparatory stage for estrus, lasting about 7-10 days. The reproductive system begins preparing for ovulation. The eggs are nearing maturity, the epithelium of the reproductive tract begins to proliferate, glandular activity begins to intensify, secretions increase, the vulva becomes congested, the vulvar opening swells, turns red and moist and smooth, and a mucus mixed with blood is discharged. Male dogs often come over attracted by the scent, but the female dog does not allow mating.

② Estrus. This is the period when the signs of estrus are most obvious and mating is accepted, lasting about 6-14 days. The vulva continues to swell and becomes softer, the discharged mucus becomes lighter in color, and the bleeding decreases or stops. The female dog actively or stops. The female dog actively approaches the male dog, and when the male dog mounts, she actively lowers her waist, turns her hindquarters toward the male dog, deflects her tail to one side, and opens and closes the vulvar opening, allowing mating. Two to three days after the start of estrus, the female dog begins to ovulate, which is the best time for mating.

③ Metestrus. The swelling of the vulva subsides and gradually returns to normal, the temperament becomes quiet, and she does not allow, becomes quiet, and does not allow the male dog to approach. This generally lasts two months, after which she enters anestrus. If she has become pregnant, the period after estrus is the gestation period.

④ Anestrus. The reproductive organs enter an inactive state. This generally lasts about 3 months, after which the next proestrus begins.

Male dogs have no regular estrus. During the breeding season when female dogs are in estrus en masse, the testes enter a functionally active state. When approaching a female dog in estrus, upon smelling the special odor of the female dog in estrus, the male dog can become aroused and complete mating.