Although cycles vary, female cats will usually go into heat for 4-5 days every 3 weeks during breeding season. As an effort to call their mates, they will yowl miserably and pee more often, and may spray urine all over the house. Unspayed female dogs will generally have a bloody discharge for about a week, and can conceive for another week or so after that. While a female is in heat, males in the area will go to great lengths to seek her out, and the female will try equally hard to escape.