Feral cats are a integral part of the ecosystem in many communities. These cats are not pet cats that are allowed outdoors for part of the day. These are cats that are much different from the pet cat that may be sharing your home.
Commonly also referred to as community cats or free-roaming cats, feral cats are accustomed to living outdoors and fending for themselves. Though it is possible to remove kittens from a feral cat colony, socialize them, and successfully rehome them, this is usually not a possibility for the majority of the adult cats. These adults do not do well in a home situation. They are not typically terribly trusting and are difficult to keep indoors. Worse, when these cats end up in shelters or rescues, they are most often euthanized as being unadoptable.
However, allowing them to remain in their colonies while continuing to reproduce is not a desirable option either. Cats reproduce very quickly, with a female cat easily capable of becoming pregnant with a new litter while still nursing her last litter. These cats simply produce too many kittens to allow rescues and shelters to capture and rehome all of them. During periods of increased breeding activity, an influx of kittens can easily overrun a shelter facility, contributing to crowding in the facility that in turn leads to increased stress and higher disease rates. This is not an acceptable situation.
Trap-neuter-release (TNR) programs though are an option for controlling these populations, an option that can be very successful if managed correctly. In order to make a difference in the effort to control the homeless cat population, at least 70% of the breeding animals need to be altered. Ideally, all individuals within the colony will be spayed or neutered. Control of food resources is also mandatory for a well-controlled TNR colony.
Essentially, in a TNR program, cats are trapped, examined for signs of disease, neutered or spayed, ear notched or otherwise marked for identification purposes, vaccinated, and then returned to the colony. Kittens and adult cats that can be socialized are removed from the colony and rehomed. These TNR colonies become relatively stable populations. They are normally relatively successful in running off newcomers to the area. However, every effort should be made to discourage the public from "dumping" other unwanted cats into the colony's territory.
In an effort to increase public awareness about feral cats and to help establish a safe place for these cats, October 16, 2013 has been declared as National Feral Cat Day. There are a host of events being planned in communities nationwide, including fundraisers, spay/neuter clinics, public education outreach events, and more. Find an event near you or register your own event by visiting the National Feral Cat Day website.