Most estimates place the number of feral cats in the country at around 60 million. While basically self-sufficient, feral cats still tend to congregate near human habitation. They know they can find food here. Where the food supply is adequate, cats gather in numbers creating colonies. The size of the colonies varies depending on food supply, but some may reach upwards of 50 animals.
Cats procreate exponentially.
An intact female may have multiple litters in a year's time. Humane organizations, wildlife biologists, veterinary associations, local governments and concerned citizens all agree that something needs to be done to curtail the population of feral cats. Until recently, most agreed that the best that could be done was to trap feral cats, try and adopt the ones that could be socialized and euthanize the rest. In the late 1970s, however, researchers in Great Britain began to experiment with other alternatives. One program that began to garner support entailed trapping feral cats, spaying or neutering them, vaccinating them and releasing them back into the colony from which they came.