Can one female cat and her offspring produce 420,000 cats in 7 years? Although dramatic, formulas predicting that the progeny of a single female cat can reach astronomical levels within a few years are not credible.
Theoretical Maximums Don’t Occur in Nature
These projections are calculated based on the theoretical maximal reproductive capacity of cats if they breed year-round, have unusually large litters and 100% survival, none of which occurs in nature.
In three different studies of more than 100,000 community cats, it was determined that individual female cats averaged 0.9-1.4 litters per year (Wallace 2006, Nutter 2004, Scott 2002). The average litter size was 3-4 kittens with a kitten mortality rate of 75% before maturity (Nutter 2004). This is similar to that of other small carnivores but higher than the 26% mortality reported in pet kittens.
Unaltered Community Cats Overwhelm Shelters
Cat reproduction is controlled by day length and is strongly seasonal. Most cats become pregnant as days get longer in February to April, delivering their kittens 2 months later. Unlike puppies, which arrive in shelters at a relatively constant rate throughout the year, kitten intake is clustered in the late spring and summer months in a phenomenon known as kitten season. This sudden increase in cat admissions commonly overwhelms shelter capacities, leading to crowding, disease, and high euthanasia rates.
Although reproduction and survival statistics vary greatly among colonies and geographic regions, the impact of unaltered community cats on the domestic cat population and intake of cats in shelters remains impressive. Cat owner surveys consistently reveal that 80-85% of pet cats are surgically sterilized compared to only 2% of community cats (Chu 2007, Wallace 2006, Levy 2003). Using these figures, community cats likely represent the single most important source of cat overpopulation, shelter intake, and kitten deaths.
Spring Pregnancy Spike Leads to Kitten Season
Pregnancy data from more than 100,000 community cats being sterilized at Trap-Neuter-Return clinics in the U.S. shows how a spike in pregnancy in the spring leads to “kitten season” a few months later.