Depending on your perspective, you may or may not be surprised to learn that one of the most controversial issues we cover here at Faunalytics is the issue of feral cats — and more specifically, what to do about them. It’s a controversial topic because it’s complicated: you have cats, a domesticated species that is beloved by millions, living in the wild and in conflict with wild bird and mammal populations, species who are beloved by conservationists and many others. It’s especially volatile because animal lovers are passionate people, and when animal lives are at stake, tempers can flare.

It’s important to note that, in practice, both groups agree on the most fundamental point: we need to reduce (or eliminate, where possible) feral cat populations, both for the quality of life of cats, and to mitigate their impact on the environment. The discussion gets divisive when it comes to how to achieve that goal. Opinions on how to deal with feral cats range from promoting capture-and-kill, to a complete laissez-faire approach, to Trap-Neuter-Return (TNR) programs, and every possible gradient of idea in between. The debate gets further enflamed because some on the wildlife conservation side are staunchly opposed to allowing any cats, even cats with guardians, outdoors, which many cat guardians see as obstinate, unrealistic, and cruel.

In this blog, we’ll look more closely at why this isssue is so important, the mechanics of this debate, and what the data says we can do about it.

Why The Issue Matters

The issue matters because feral cats’ impact on the environment is undeniable. Though there is certainly a debate about the extent of the impact, we can be sure that the millions of cats living in the wild around the world and hunting wildlife do have an effect of some kind.

The two main factors to consider when thinking about feral cats’ impact is their population size, and how many animals each one kills. We know that unfixed cats can reproduce exponentially up to a point, meaning their population can increase very much in a very short amount of time. At a certain point, however, their population reaches a carrying capacity where there simply aren’t enough resources in the local environment to support a larger population. Carrying capacity is something that varies depending on local ecology, and is not an easy thing to generalize across an entire continent or country, for example.

The International Union for Conservation of Nature (IUCN) — one of the world’s foremost conservation organizations — lists domesticated cats as among the 100 “worst invasive species.” Meanwhile, an analysis of IUCN data suggests that feral cats have contributed to at least 14% of the 238 global vertebrate extinctions that the IUCN has recorded, and currently threaten 8% of the 464 species that the IUCN lists as critically endangered. On the other hand, some have argued that the idea that cats are threatening global biodiversity constitutes a “moral panic,” citing studies that show that feral cats can have an impact on wildlife populations, but far from the extent that would suggest an emergency.

Most of the estimates of the populations of feral cats around the world are just that: estimates. This is exacerbated by the fact that feral cats are generally cagey and good at hiding, making their numbers hard to pin down. While estimates and models are not problematic in and of themselves, it’s important to note that estimates aren’t statistics. In North America, some estimates of cat populations range from 50-150 million individuals, while others estimate 30-80 million feral cats with another 40 million household cats with outdoor access. In either case, these estimates are broad-ranging and reflect the inherent difficulty of gathering the data.

Meanwhile, estimating the impact of feral cats depends at least in part on population estimates, as fraught as they may be. One of the most often-cited estimates of feral cat impact comes from a 2013 study that concludes that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3–22.3 billion mammals annually, and that feral and stray cats account for the majority of that impact. Again, the range represented above is enormous, but it’s easy to see that even at the low range, the problem is a significant one. Even if the impact of free-ranging cats is half of the lowest estimate — even if the alarming impact of feral cats is a “moral panic” — it’s a problem that begs for a solution.

The Debate: A Masterclass In Ethics

There are three primary ethical dimensions to the debate about feral cats: the first dimension, which most people agree on, is that feral cats hunt, maim, and kill local wildlife, and because cats are domesticated and have no ecological “place” per se, this is an ethical wrong; the second dimension encompasses the ethics of how to reduce or eliminate feral cat populations, and whether that can be done humanely, or whether it must be done lethally (and whether that’s even effective); the third dimension brings in the broader issue of the impact of outdoor cats with guardians, and whether keeping them away from the outdoors constitutes deprivation or cruelty.

When discussing ethical tradeoffs like the ones outlined above, there are rarely easy answers, as they often come down to valuing certain lives more than others. It’s worth noting here that people have written articles that truly run the gamut, from strong ethical defenses of TNR, to stringent defenses of the rights of all cats to enjoy at least some of their lives outdoors. There are also those who have noted the effectivness of TNR, but argue that the quality of life of cats neutered and returned to the wild represents an ethical dilemma in and of itself.

You may have noticed that in the above, we haven’t included justifications for lethal management, despite the existence of literature which advocates strongly for such an approach. While lethal programs clearly can reduce cat populations, they do so through death and suffering, and it is hard to imagine an “ethical” program for what amounts to mass culling. Furthermore, lethal management does not actively address the possibility of exponential reproduction, and, considering that cats are crafty and good at hiding, it may be virtually impossible to implement a lethal control program that can “solve” the issue in a comprehensive way. Sterilization must be a component of a longer-term solution.

When it comes to the will of the people, public opinion is generally supportive of ethical and humane approaches, with lethal options being the least desirable. This is no doubt bolstered by the fact that many people have cats as companion animals and likely do not want to see the suffer needlessly. A recent review of public opinion found that, depending on the survey, support for capture and kill methods ranges from about 15-25%, while support for humane methods like TNR are generally in the majority, ranging from 68-72%. The same review noted that this support seems to be trickling up institutionally as well: the American Public Health Association’s Veterinary Public Health Special Primary Interest Group has deemed TNR to be “the preferred method of management wherever feasible,” while the American Veterinary Medical Association officially changed its position on community cat control in 2016 to be more supportive of TNR efforts.  

Evaluating The Strategies

Fortunately, animal advocates who recognize the complicated ethics of this issue have been working hard to analyze possible solutions that will satisfy as many of the ethical dimensions of the issue as possible. As we look at effectiveness, keep in mind that if we want to value animal life equally, the best solution will empirically decrease feral cat numbers, and by extension wildlife deaths, in the most humane way possible. For that reason, lethal control methods are off the table.

A second approach that some advocate for is a kind of “Trap-Neuter-Adopt” approach, or Trap-Remove, the purpose of which is to take feral cats out of the community, help them to become adoptable, and essentially take them out of the equation by transforming them to indoor cats. This approach is attractive because it seems to address all of the ethical concerns we have: it can lower free-roaming cat populations, and it takes them out of the context where they can kill wildlife immediately. However, there is little data that speaks to the effectiveness of Trap-Neuter-Adopt, and these programs generally also include euthanizing / killing the cats who are not adoptable. This is a major problem, because feral cats are, quite simply, often terrible candidates for adoption. Taking them out of the wild context where they have grown and formed bonds away from humans is a high-effort endeavor with low return on the investment of time and energy.

Finally, we come to Trap-Neuter-Return (sometimes also implemented as Trap-Neuter-Vaccinate-Return, or Trap-Neuter-Return-Monitor) programs. The TNR approach is generally satisfactory from an ethical standpoint: it involves some disruption of cat lives but it is not lethal; its primary purpose is to suppress feral cat populations, which reduces the overall suffering of feral cats; and, in doing so, it reduces the suffering and death that feral cats inflict on local wildlife. But is it effective?

A quick scan of the Faunalytics library shows a range of articles about TNR, and the data they reveal is encouraging. Among the highlights:

• An “iconic” TNR program that was carried out in Newburyport, Massachusetts beginning in 1992 helped to shrink a thriving and long-standing feral cat population from 300 in its heyday to, ultimately, zero.
• Citizen scientists reviewing a TNR program in Chicago found that colony populations declined by 54% from entry and 82% from peak levels, consistent with findings from other local programs.
• A TNR study on the University Of Central Florida campus found the campus community cat population had declined by a total of 85% from 1996-2002, with continuous reduction year after year. What’s more, the initial reduction persisted into the future. From 2002 to 2019, the number of stray and feral cats declined an additional 57%.
• A review of 13 different cat management programs found that four long-term TNR programs, which lasted from 9 to 20 years, met with great success: cat populations decreased by between 54% and 100%.
• A review of comprehensive data from six municipal TNR programs in the U.S. found that overall cat euthanasia at all shelters decreased by a median rate of 83%, with kitten euthanasia decreasing by a median of 87%. Cat intake dropped by a median of 32% and kitten intake a median of 40%.

Moving Forward

In any passionate debate, there will always be a certain constituency of people who simply will not change their opinions, regardless of the data. While there has been some research on the attitudes of community cat caretakers and bird conservationists and how we might bring them together, more coalition-building clearly needs to be done.

Whether we’re engaged with this issue on the frontlines or the sidelines, keeping our eye on the data and not getting sidelined by division and emotions is crucial, as animal lives hang in the balance. As we can see above, data is increasingly pointing to the positive outcomes that well-implemented TNR programs can provide. As data-driven advocates, we should be paying attention and moving forward accordingly, always being open to data that shows how we can adjust and improve. While we can embrace TNR for its effectiveness, it’s important we take some of the ethical concerns around TNR and feral cats’ quality of life seriously, and continually work to improve such programs.

TNR is increasingly emerging as an ethical and effective solution to a fraught problem, and it’s one where animal advocates and citizens alike can get actively involved. It’s important to note that TNR advocates face immense pressure and high degrees of stress. As animal advocates, it’s important to take care of ourselves if we’re engaged in this kind of work to avoid burnout, and if we’re not engaged in this work, we need to do what we can to support our friends on the frontlines. Reducing free-roaming cat populations worldwide is going to be a long struggle, one that may never truly be “won,” but instead fought back to a low simmer. Fortunately, data on TNR is helping to provide a roadmap for how we might do so. Being prepared (and supported) emotionally will help us continue to see the work through.