Cats, on average, have somewhere between three to five kittens per litter. Their gestation period is somewhere around sixty-four to sixty-six days, a little over two months. Kittens are usually weaned anywhere from eight to twelve weeks, or when they are eating solid food and can be removed from their mother. A typical female cat is capable of having two to three litters of kittens per year. An average breeding life for an adult female cat is around ten years. This would put the maximum amount of kittens produced by a cat at around sixty to one hundred and fifty kittens over a ten year period. This high rate of kitten production is usually controlled by cat owners by spaying and neutering, where the female and male of the species are rendered incapable of kitten production. There are an estimated sixty million feral cats in the United States alone, the former pets of American cat owners that were either neglected or thrown out of their homes. Female cats typically will come into a period of heat every two weeks, with the period of heat lasting four to seven days.