do dogs have periods

Dogs do not have periods like humans do, but female dogs do go through a heat cycle (estrus) during which they can have some vaginal bleeding or discharge. This bleeding is part of their reproductive cycle and typically lasts from about 3 to 12 days within a heat cycle that spans around 2 to 4 weeks. Female dogs usually reach sexual maturity and start having heat cycles around 6 to 12 months of age, depending on breed and size. Unlike humans, female dogs do not have monthly menstruation; their heat cycles typically occur every 6 to 12 months, or a few times a year depending on the dog. Also, the bleeding in dogs is not caused by shedding the uterine lining as in humans, but rather by hormonal changes associated with the preparation for potential pregnancy. Spaying a dog stops the heat cycles, but some bleeding might occur briefly after the surgery due to hormonal changes.