Critical Assessment of Claims Regarding Management of Feral Cats by Trap–Neuter–Return

Abstract

Many jurisdictions have adopted programs to manage feral cats by trap-neuter-return (TNR), in which cats are trapped and sterilized, then returned to the environment to be fed and cared for by volunteer caretakers. Most conservation biologists probably do not realize the extent and growth of this practice and that the goal of some leading TNR advocates is that cats ultimately be recognized and treated as "protected wildlife." We compared the arguments put forth in support of TNR by many feral cat advocates with the scientific literature. Advocates promoting TNR often claim that feral cats harm wildlife only on islands and not on continents; fill a natural or realized niche; do not contribute to the decline of native species; and are insignificant vectors or reservoirs of disease. Advocates also frequently make claims about the effectiveness of TNR, including claims that colonies of feral cats are eventually eliminated by TNR and that managed colonies resist invasion by other cats. The scientific literature contradicts each of these claims. TNR of feral cats is primarily viewed and regulated as an animal welfare issue, but it should be seen as an environmental issue, and decisions to implement it should receive formal environmental assessment. Conservation scientists have a role to play by conducting additional research on the effects of feral cats on wildlife and by communicating sound scientific information about this problem to policy makers.

The impact of free-ranging domestic cats on wildlife of the United States

“…Threatened species in close proximity to cat colonies-including managed TNR colonies 11,12 -face an especially high level of risk; therefore, cat colonies in such locations comprise a wildlife management priority. Claims that TNR colonies are effective in reducing cat populations, and, therefore, wildlife mortality, are not supported by peer-reviewed scientific studies 11 .…”

“…Mounting evidence from three continents indicates that cats can also locally reduce mainland bird and mammal populations [5][6][7] and cause a substantial proportion of total wildlife mortality [8][9][10] . Despite these harmful effects, policies for management of free-ranging cat populations and regulation of pet ownership behaviours are dictated by animal welfare issues rather than ecological impacts 11 . Projects to manage free-ranging cats, such as Trap-Neuter-Return (TNR) colonies, are potentially harmful to wildlife populations, but are implemented across the United States without widespread public knowledge, consideration of scientific evidence or the environmental review processes typically required for actions with harmful environmental consequences 11,12 .…”

Distribution characteristics of unmanaged cat colonies over a 20 year period in Auckland, New Zealand

“…However research indicates that public support for TNR is less strong in New Zealand (Farnworth et al, 2011) when compared to other countries (Natoli et al, 2006). A recent review of TNR has also concluded that many of the claims made in its support are either not broadly applicable, demonstrably false or unquantifiable (Longcore, Rich, & Sullivan, 2009). Whether or not this is the case, there is little evidence that on-going TNR programs result in extinction of colonies (Slater et al, 2008b).…”

Bartonella and Toxoplasma Infections in Stray Cats from Iraq

“…3 During Operation Iraqi Freedom, the US military occupation of Army bases provided new sources of food and water for stray dogs and cats, 3 which elevated the concern that stray animals in close contact with military troops could serve as a reservoir for zoonotic agents, because high densities of feral cats have been shown to increase the incidence of such pathogens. 4,5 Studies have also shown that deployed military personnel in enzootic environments have a higher risk of contracting zoonotic diseases because of increased animal contact or associated animal exposure. 6 Therefore, the US Department of Defense established an animal control program early in the Iraqi campaign that involved the trapping and euthanasia of feral cats and dogs in Baghdad's Green Zone and on US military installations.…”