420,000 Kittens? The Unspayed Cat To Kitten Calculator

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No matter how you do the math, there are too many cats/kittens and too few homes. This calculator attempts to (loosely) apply math calculations to scientific principles as they relate to cat reproduction. Taken into consideration are factors such as a high percentage of owned cats are neutered and a small percentage of feral cats are neutered. Also factored in are annual mortality rates as well as post-weaning survival rates of kittens.

At seven years, the calculator shows 2905 kittens at 7 years (versus 420,000) and 49,000 at 10 years. But no rationale person would think that 2905 kittens produced by one cat and her offspring in 7 years is acceptable. Responsible pet owners should spay or neuter their pets.

Factors:

  • The average mature cat can have 3 litters with a total of 12 kittens per year; 10.2 surviving kittens of which 4.7 are female
  • The average litter size is 4 kittens with 15% loss before reaching weaning age (3.4 kittens per litter)
  • Gender ratio per litter averages of males to females is roughly 46.5% female (of 3.4 kittens = 1.8 males and 1.6 females)
  • 35% spay ratio allowance for offspring (unscientific factor balancing owned and stray cats)
  • 20% annual mortality ratio

    Not factored into this equation:

  • An immature cat's first litter usually consists of 2 kittens versus 4.
  • Unspayed female cats can begin reproducing at 6 months of age and can produce a litter during the same year of birth.
  • 30% feral mortality
    • YearFemale CatsMinus Died1
    (@ 20% mortality)    		Minus Spayed2
    (@ 35% spayed)    		Breeding Female Cats# Kittens Born# Surviving Post Weaning3Surviving Female Kittens4
    Year 10 - 0 - 01 female cat will have 12 kittens 10 will survive and 5 will be females
    Year 26 - 1 - 23 female cats will have 31 kittens 26 will survive and 12 will be females
    Year 315 - 3 - 57 female cats will have 79 kittens 67 will survive and 31 will be females
    Year 438 - 8 - 1317 female cats will have 203 kittens 172 will survive and 80 will be females
    Year 596 - 19 - 3443 female cats will have 519 kittens 442 will survive and 205 will be females
    Year 6247 - 49 - 86111 female cats will have 1332 kittens 1132 will survive and 527 will be females
    Year 7633 - 127 - 222285 female cats will have 3417 kittens 2905 will survive and 1351 will be females
    Year 81623 - 325 - 568730 female cats will have 8766 kittens 7451 will survive and 3465 will be females
    Year 94164 - 833 - 14571874 female cats will have 22484 kittens 19112 will survive and 8887 will be females
    Year 1010680 - 2136 - 37384806 female cats will have 57672 kittens 49021 will survive and 22795 will be females
    1http://www.animalsandsociety.org/assets/library/199_s15327604jaws07041.pdf
    2http://catvet.homestead.com/devon_rex_project_report_1st_year.doc
    3http://la.rsmjournals.com/content/4/1/99.full.pdf
    4http://www.royalcanin.us/library/catlittersize.aspx

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