The proestrus averages nine days, though anything between 1 to 17 days is still normal. The estrus lasts an average of nine days also, with 3 to 21 days still being normal. B****es often have a blood-tinged discharge beginning in proestrus and it will become straw colored during estrus. Unlike the human female cycle, this is when the b**** is fertile. In humans, the menstruation is after the fertile phase.
You need to keep your b**** away from other dogs, take her outside on a leash, and don't leave her anywhere an intact male could climb, dig, or chew his way in.