In a new article published in Conservation Science and Practice, Michael Calver and a host of his fellow TNR opponents claim to “present unequivocal evidence” that TNR “harms cat welfare… threaten[s] wildlife and public health, and exacerbates rather than controls rodent problems” [1]. It’s not every day you hear scientists use the term unequivocal evidence, unless maybe it’s Andrew Wakefield or Elizabeth Holmes. Still, the basic proposal here is straightforward enough: compared to at least one other method for managing free-roaming cats, TNR performs worse on the measures in question.

So, do the authors deliver on their promise?

They don’t even bother to try. Instead, Calver and his co-authors resort to the kind of misrepresentation, misdirection, and outright gaslighting we’ve come to expect.

Unequivocally equivocal

Despite the lofty ambitions of the paper’s abstract, it doesn’t take a reader very long to see just how wobbly the evidence presented is. As to “whether TNR programs improve cat health,” for example, the “research varies” [1]. The authors also admit that “less is known of declines in wildlife populations following infection” with Toxoplasma gondii, and that at least some researchers “regarded it as a hypothesis for wildlife decline in Australia rather than an established cause” [1]. And the authors of one study cited by Calver et al. as evidence of “poor health outcomes” associated with TNR admitted that “providing disease diagnostics was beyond the scope of our study” [2].

What about the “studies correlating cat density with prey density”? Calver et al. [1] admit they’re  “often inconclusive because of confounding variables such as other threats or habitat variation, not to mention analytical challenges.”

Unfazed by their own doubts, though, Calver et al. press on.

Among the studies cited as evidence of “high predation pressure” are one in which predation levels were simply exaggerated beyond levels supported by the data, another in which no predation was observed at all, and still another in which the researchers employed taxidermied wildlife and a plush cat toy to examine the “sub-lethal impacts” of cats. (More troubling is the fact that their results are contradicted by empirical evidence gathered over more than 50 years.) Predation levels are further exaggerated by citing studies in which prey tally details were deliberately obfuscated or for which the cats recruited were “confirmed by their owners as being active hunters.”

Calver et al. [1] complain that “health checks are declining among [TNR] practitioners.” But the one study cited to support the claim was a snapshot in time, with no way to determine any such trend (Aeluro et al., 2021).

It goes on and on and on. So much for the “unequivocal evidence” we were promised.

(Mis)management Implications

Naturally, the evidence isn’t an end in itself; it’s being used to lobby for the authors’ preferred management method: more killing. They don’t come right out and say that, of course, but that’s where they’re going with all this. We’ve seen this movie before.

Although Calver et al. argue that “management implications are context-specific,” the examples they cite come from all over the place—parts of Rome, for example, where cats are found at high densities [3]; the Australian outback, where densities are very low [4]; and Washington, DC, where the population of free-roaming cats is a fraction [5] of what had been suggested a year earlier. Nowhere do they address the important differences in context—or the associated management implications.

Here again, they don’t even make an attempt. Indeed, their proposed management option is very much one-size-fits-all: “intensive adoption programs” with “responsible euthanasia” for cats who aren’t adopted [1].

Of course, as almost anybody familiar with the issue will readily attest, we’ve been trying to adopt our way out of “the feral cat problem” for generations now. But there’s no evidence that the “traditional” approach to managing free-roaming cats has done anything to reduce their numbers; it’s the poster child for failed public policy.

Filling shelters with cats—as Calver et al. propose—would almost certainly result in millions of cats being killed as they await adopters unlikely to materialize.

It would be a return to the mid-80s, when 7.8–12.9 million of the 10.7–17.8 million cats entering U.S. shelters were killed [6]. Or the mid-90s, when 70 percent of the estimated 1.4–1.6 million cats brought to shelters were killed there [7].

An again, there’s no reason to think that the number of free-roaming cats would be reduced.

Incredibly, Calver et al. [1] arrived at their management recommendation “based on [their] collective experience.” Exactly what experience this is remains an open question. I don’t know that any of the paper’s authors have worked a day in a shelter* or engaged in any meaningful way with the staff they expect to do the dirty work. It’s no secret that the stresses associated with shelter work causes well-being to suffer [see, for example, 8–10].

At best, it’s magical thinking. I suspect it’s worse than that, though: shelter staff are merely collateral damage in their Campaign of Killing.

Why Bother?

Again, the basic proposal put forward by Calver et al. is that TNR doesn’t perform as well as other methods of managing free-roaming cats. But they fail to provide the comparison(s) necessary to draw such a conclusion. The paper’s section on  cat welfare, for example, begins with a comparison of “cats contained on their owner’s property” to “cats ranging unrestricted” [1]. The section on public health, too, focuses on outdoor cats broadly rather than on TNR. And the section on predation doesn’t refer to TNR at all.

I’m not sure what the authors are hoping to accomplish with an article like this—maybe just give like-minded individuals some “unequivocal evidence” to point to (without the burden of having to do their own homework). In any case, there doesn’t seem to be any downside.

After all, an essay that fails to provide support for its central thesis—something that wouldn’t pass muster in a decent middle school writing course—was published. No doubt there are more to come. Meanwhile, the authors continue to receive grants (often courtesy of taxpayers) and train future generations of researchers. All without the slightest criticism (at least publicly) from their colleagues in the conservation community.

So, why bother? Why not?

* If I’m wrong about this, somebody please feel free to correct the record in the comments.



  1. Calver, M.C.; Cherkassky, L.; Cove, M.V.; Fleming, P.A.; Lepczyk, C.A.; Longcore, T.; Marzluff, J.; Rich, C.; Sizemore, G. The Animal Welfare, Environmental Impact, Pest Control Functions, and Disease Effects of Free-Ranging Cats Can Be Generalized and All Are Grounds for Humanely Reducing Their Numbers. Conservation Science and Practice 2023, n/a, e13018, doi:10.1111/csp2.13018.
  2. Castro-Prieto, J.; Andrade-Núñez, M.J. Health and Ecological Aspects of Stray Cats in Old San Juan, Puerto Rico: Baseline Information to Develop an Effective Control Program. P R Health Sci J 2018, 37, 110–114.
  3. Natoli, E.; Maragliano, L.; Cariola, G.; Faini, A.; Bonanni, R.; Cafazzo, S.; Fantini, C. Management of Feral Domestic Cats in the Urban Environment of Rome (Italy). Prev Vet Med 2006, 77, 180–185.
  4. Doherty, T.S.; Dickman, C.R.; Johnson, C.N.; Legge, S.M.; Ritchie, E.G.; Woinarski, J.C.Z. Impacts and Management of Feral Cats Felis Catus in Australia. Mammal Review 2017, 47, 83–97, doi:10.1111/mam.12080.
  5. Cove, M.V.; Herrmann, V.; Herrera, D.J.; Augustine, B.C.; Flockhart, D.T.T.; McShea, W.J. Counting the Capital’s Cats: Estimating Drivers of Abundance of Free-Roaming Cats with a Novel Hierarchical Model. Ecological Applications 2023, 33, e2790, doi:10.1002/eap.2790.
  6. Moulton, C.; Wright, P.; Rindy, K. The Role of Animal Shelters in Controlling Pet Overpopulation. J Am Vet Med Assoc 1991, 198, 1172–1176.
  7. Zawistowski, S.; Morris, J.; Salman, M.D.; Ruch-Gallie, R. Population Dynamics, Overpopulation, and the Welfare of Companion Animals: New Insights on Old and New Data. J Appl Anim Welf Sci 1998, 1, 193–206, doi:10.1207/s15327604jaws0103_1.
  8. Andrukonis, A.; Hall, N.J.; Protopopova, A. The Impact of Caring and Killing on Physiological and Psychometric Measures of Stress in Animal Shelter Employees: A Pilot Study. Int J Environ Res Public Health 2020, 17, doi:10.3390/ijerph17249196.
  9. Andrukonis, A.; Protopopova, A. Occupational Health of Animal Shelter Employees by Live Release Rate, Shelter Type, and Euthanasia-Related Decision. null 2020, 33, 119–131, doi:10.1080/08927936.2020.1694316.
  10. Scotney, R.L.; McLaughlin, D.; Keates, H.L. A Systematic Review of the Effects of Euthanasia and Occupational Stress in Personnel Working with Animals in Animal Shelters, Veterinary Clinics, and Biomedical Research Facilities. J Am Vet Med Assoc 2015, 247, 1121–1130, doi:10.2460/javma.247.10.1121.

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