Feral cats are controlled or managed by various agencies to manage disease, Control of feral cats can be managed through trapping and euthanasia or other forms of lethal control, or, some claim, through
trap-neuter-return (TNR). Literature reviews have found that, in the instances where studies documented TNR colonies that declined in population, those declines were being driven primarily by substantial percentages of colony cats being permanently removed from colonies by some combination of re-homing and euthanasia on an ongoing basis. The population of TNR colonies may not decrease significantly because reproduction and immigration can outpace sterilization rates. Trap-neuter-return involves trapping feral cats, vaccinating, spaying or neutering them, and then returning them to the place where they were originally trapped. TNR programs are prevalent in several countries, including England, and are supported by many local and state governments. Proponents of TNR argue that it is effective in stopping reproduction and
reducing the population over time. TNR results in fewer complaints, as nuisance behaviors diminish following neutering, TNR is popular, but there's little evidence that TNR by itself can control the growing population of free roaming cats. The International Companion Animal Management Coalition advocates for TNR as a humane method of controlling feral cat populations. In the U.S., the practice is endorsed by the
Humane Society of the United States. and the National Animal Control Association, TNR is opposed by the
Australian Veterinary Association, the
National Audubon Society, the
National Wildlife Federation, the
Cornell Lab of Ornithology, the
American Association of Wildlife Veterinarians, the
Wildlife Society, the
American Bird Conservancy, and
PETA. Some
U.S. military bases have TNR programs, but the
United States Navy prohibits such programs on Navy land. In the US, the
American Veterinary Medical Association (AVMA), in 2016, adopted a resolution that "encourages collaborative efforts to identify humane and effective alternatives to the destruction of healthy cats for animal control purposes, while minimizing their negative impact on native wildlife and public health." The AVMA voiced support for "properly managed [feral cat] colonies" outside "wildlife-sensitive ecosystems" but stated that "[t]he goal of colony management should be continual reduction and eventual elimination of the colony through
attrition." In contrast, the number of pet cats in the US stands at approximately 76 million. The effectiveness of both trap-and-euthanise and TNR programmes is largely dependent upon controlling immigration of cats into cleared or controlled areas; where immigration of new cats is controlled, both techniques can be effective. However, where immigration is not controlled, culling is more effective. Comparisons of different techniques have also found that trap-and-euthanise programmes are half the cost of TNR ones. An analysis of both techniques in Hawaii suggested they are less effective when new cats were introduced by the abandonment of pets. The usefulness of TNR is disputed by some scientists and conservation specialists, who argue that TNR is only concerned with cat welfare and ignores the ongoing damage caused by feeding outdoor populations of neutered cats, including the depredation of wildlife, transmission of diseases, and the accumulation of cat faeces in the environment. Conservation scientists also question the effectiveness of TNR at controlling numbers of feral cats. Some studies that have supported TNR have also been criticised for using anecdotal data to evaluate their effectiveness. In order for TNR to reduce the cat population, sterilisation rates of at least 75% must be maintained at all times, particularly because TNR practitioners providing cats with food makes the problem worse by increasing the survival rate of feral kittens. Also, this food source causes other cats to be drawn into the colony from outside. Members of the public often begin dumping unwanted pet cats at TNR sites, increasing the rate of recruitment. And neutered cats are less territorial, allowing for higher populations. TNR programs are sometimes able to attain local reductions in the numbers of cats at specific colony locations, but it has never been demonstrated to meaningfully impact cat populations over large areas or regions, because the effort necessary to maintain sufficient sterilisation rates means that systemic TNR will never be a credible option. For example, to reduce a typical Australian city's population of 700,000 feral cats through TNR would require sterilising at least 500,000 of them initially, and then continuing to sterilise more than 75% of the kittens that the other 200,000 would continue to produce each year indefinitely, along with all the new recruits from other cat populations drawn by the food supply. TNR is backed by well-funded advocacy organizations: in 2010,
Alley Cat Allies spent
US$3 million advocating to legalise TNR throughout the United States, while the
Best Friends Animal Society spent $11 million on a "Focus on Felines" initiative that included TNR advocacy. Promoters of TNR are often funded by big businesses with a commercial interest in selling cat food, While TNR is a popular approach to resolving the over population problem, it is not a ubiquitously accepted method. Another perspective emphasizes the poor outdoor living conditions of feral cats and advocates for rehoming, adoption, or euthanasia as a more ethical response. This perspective centers the pressure feral cats place on the ecosystem, which is alternative to the popular position that centers the value of each cat's life.
TNR and wildlife De-sexing cats, as in TNR programs, does nothing to prevent them from continuing to destroy wildlife. In
Mandurah, Western Australia, a single, neutered, semi-feral cat raided a protected
fairy tern colony on at least six nights in November 2018. It killed at least six breeding adult fairy terns; directly or indirectly killed at least 40 nestlings, and caused enough stress on the fairy tern colony that all 111 nests were abandoned; resulting in a complete breeding failure for the entire colony of threatened seabirds. The predation was documented by wildlife cameras, as well as by the presence of cat tracks, cat scat, decapitated fairy terns, and injured and missing fairy tern nestlings. Though the colony was surrounded by ultrasound generators intended to deter cats, the fairy tern colony might have been an irresistible target, and this particular cat was white and had a blue eye, traits commonly associated with deafness.
Management in sensitive environments In sensitive environments, such as delicate ecosystems that have been degraded by feral cats, population management can be quite difficult. On isolated Pacific islands, trapping and removing the feral population too quickly can have adverse effects including booms in rodent and small reptile populations previously checked by the feral cat population. This new dynamic may prove to be more harmful, with further upstream effects on the ecosystem that were not predicted before removal of the feral cat population. With such a sensitive system to account for, solutions for population control will likely differ from case to case, and especially in different ecosystems where feral cats are to be controlled. == Effects on wildlife ==