These free roaming, unaltered cats are very prolific. Feral kittens have a high mortality rate. Those kittens who survive can begin to reproduce as young as four months of age and will continue the cycle of producing more unwanted litters. This proven effective worldwide method of population control DOES NOT depend on ethically questionable euthanasia.
Cats DO perform a valuable function in a community by effectively controlling the rodent population.
It is a well known fact that the European bubonic plague epidemic of medieval times was largely due to the HUGE rat population. Rats were the carriers of the plague. Because cats were associated with witchcraft during that time, and killed in vast numbers, rat overpopulation was the result. Cats are fastidious by nature. They groom themselves meticulously, and most cats prefer to bury their waste.