To quote Dog Fancy magazine, Feb 2000 issue:
"An unspayed female dog and her mate, and all their puppies if none are ever nuetered or spayed, add up to:
1 year -- 16 dogs
2 years -- 128 dogs
3 years -- 512 dogs
4 years -- 2,048 dogs
5 years -- 12,288 dogs
6 years -- 67,000 dogs."
Think about that!!! wow! I would never have a dog that wasn't spayed or neutered, I just don't want to deal with the heat and etc.