Your dog can come into her first heat any time between 6 and 24 months. According to Webvet.com, small dogs come into heat sooner than larger breeds. Typically she will have two estrus cycles, or heats, a year, and each one lasts for between 18 to 24 days. read more
Dog menstruation is a misnomer, since dogs do not menstruate. The estrous cycle in dogs consists of four major phases: proestrus, estrus, diestrus, and anestrus. A dog’s vagina discharges blood and other fluids during the first two of these phases, most heavily during proestrus. read more
The season in a female (dog!), which happens, on average, 6 monthly (some bitches cycle with longer intervals) lasts 21 days, again on average. They are normally ready to be mated at around day 10 to 13. read more