A female dog’s season, also referred to as estrus or heat cycle, is the time where she is receptive to mating. During this time, estrogen levels increase and then decrease before eggs release from the ovaries. Unlike human females who undergo menstruation every 28 days on average, the average female dog goes into heat twice a year. Knowing the signs of estrus lets you know when your dog is in heat and enables you to avoid unwanted pregnancies.
Signs of Estrus
Your puppy’s first estrus typically occurs between 6 and 24 months of age. You may notice that your dog appears nervous and more alert. Frequent urination is common, as is apparent marking with urine. The external vulva may appear swollen. During the first 7 to 10 days of the heat cycle, you may notice a bloody discharge. How much blood appears varies by dog and their grooming behavior. After this point, the discharge changes to watery, yellowish color. At this point, she is receptive to mating. A typical heat cycle lasts 18 days.