A cat colony is a population (or "clowder") of feral domestic cats (not to be confused with wild cats). Members of a feral cat colony can include cats that have strayed after living with human caretakers as well as their offspring, which have had little human contact or none at all. Established feral colonies are located worldwide.
The term is used primarily when a noticeable population of feral cats live together in a specific location and utilize a common food source—such as food scavenged from refuse bins, dumpsters or supplementary feeding by humans—and reach a population density which might be regarded to be undesirable. However, some who work with feral cats will refer to a smaller population of cats (even as few as a single cat) as a colony if the cats are regularly present at a specific location, especially if they receive care by a human. The term is not typically applied to solitary cats passing through an area.
Feral colonies occur when unsterilized domesticated cats become, intentionally or otherwise, disconnected from their respective human owners and managed domestic environment. They quickly have to learn to fend for themselves and form the breeding communities subject to this article. Feral cat colonies typically arise when changes in human activity create an opportunity for existing baseline feral cat populations to form a locally concentrated group. For example, the opening of a new restaurant can allow for easily gained food via unprotected garbage cans. The greater the food source, the larger a feral colony will become. Feral cat population expansion can be quite rapid.
The multiple, managed, feral colonies at the Colosseum in Rome exceed 250 cats, and have achieved considerable notoriety.
Although cats are traditionally believed to be loners, even despising the company of other cats, these colonies can actually increase the chances of survival with multiple cats to look after kittens. In addition, some cats seem to enjoy the company of others, especially those born as domestic.
When a feral colony grows to a large size, those living or working nearby might consider the presence of a locally concentrated cat population to be a nuisance. Complaints made include:
- Urine spraying to mark territory
- Digging in gardens and feces left by the cats
- Noise made by fighting and mating cats
- Predation upon wildlife
- Diseases transmissible to humans (zoonoses)
- Diseases transmissible to pets
- The poor state of health of the cats in the clowder
- The likelihood of population growth
- Being preyed by larger, more dangerous wildlife like feral dogs,coyotes, wolves or bears.
Those who consider these cat colonies to be a nuisance traditionally have attempted to eliminate them by requesting that municipal or private pest control services trap the cats and remove them (typically to be euthanised). In rural areas, some complainants will attempt to exterminate the cats themselves (typically with firearms). However, if the factors that allowed the colony population to grow in the first place are not addressed as well, a new clowder can form in the same location when cats that escaped trapping and those moving in from surrounding areas continue to breed. This is referred to as the "vacuum effect".
More recently, a number of animal welfare organizations have begun to employ the "Trap-Neuter-Return" (TNR) method to deal with the issue of feral clowders, sometimes with the support of local municipalities. This approach includes sterilization of the cats to prevent breeding, removal (and euthanasia) of sick or injured cats (this part of the TNR method does not always take place), vaccination, marking, and return of healthy cats to the site, and rescue of kittens and other tame cats to adoptive homes. Groups promoting this approach believe that it addresses many of the concerns of those who might otherwise consider the colony a nuisance, and provides a palatable alternative for cat lovers who might otherwise take no action to prevent the population from growing.
Unlike wild predators, feral cats in managed colonies are not affected by food pressures, and usually exist in population densities far higher than is the case with animals that will starve or fall prey to diseases if their numbers outstrip the available supply of prey.
A colony in which the TNR method is being used to sterilize the cats and that is under the regular care and observation of a caretaker is referred to as being managed.