And yet.

If all the “birds” are real, how do we account for there being more dead birds than live ones in the U.S.? And why isn’t anybody talking about that?

Based on the best available evidence, researchers estimate there about 7 billion birds in North America during the pre-breeding season (i.e., adults), with roughly 5.7 billion (excluding coastal and wetland species) found in the Lower 48 [2]. It’s quite difficult to reconcile such a figure with the “conservative” estimate, made six years earlier, that “free-ranging domestic cats kill 1.3–4.0 billion birds” year in and year out in the contiguous U.S. [3].¹ That’s in addition to the mortalities attributable to building collisions (365–988 million birds [4]), collisions with vehicles (89–340 million birds [5]), power lines (8.9­–68.6 million birds [6]), and wind turbines (140,000–328,000 birds [7]). And if we take into account the research suggesting that wind turbine estimates might be four times greater than previously suggested [8], total U.S. bird mortalities from collisions with buildings, vehicles, power lines, and wind turbines could be as high as 1.4 billion annually.²

But that doesn’t account for a study published last year that adjusted upward—and considerably—the number of bird deaths caused by building collisions: “minimally” 1.3–3.5 billion, but perhaps as many as 5.2 billion annually [9].

For those keeping track at home, these sources of bird mortality (including the inflated, agenda-driven “estimate” for free-roaming cats) total at least 2.8 billion—and up to 9.6 billion on the high end.³ Not all of these birds are adults, of course. Still, reconciling these figures with an adult population estimated to be just 5.7 billion requires the kind of creative accounting that would put Lehman Brothers to shame.

You know who’s not keeping track at home? The usual suspects eager to see more cats killed—the American Bird Conservancy, Audubon Society, The Wildlife Society, and Smithsonian Institution among them. When the “estimates” for free-roaming cats were published, in 2013, these organizations went out of their way to ensure that the media lost their collective minds.⁴ So where were they last April, when the estimated bird deaths attributed to building collisions surpassed those attributed to cats?

[Cue the chirping crickets…]

Literature cited

1. Lorenz, T. Birds Aren’t Real, or Are They? Inside a Gen Z Conspiracy Theory. The New York Times 2021.
2. Rosenberg, K.V.; Dokter, A.M.; Blancher, P.J.; Sauer, J.R.; Smith, A.C.; Smith, P.A.; Stanton, J.C.; Panjabi, A.; Helft, L.; Parr, M.; et al. Decline of the North American Avifauna. Science 2019, eaaw1313, doi:10.1126/science.aaw1313.
3. Loss, S.R.; Will, T.; Marra, P.P. The Impact of Free-Ranging Domestic Cats on Wildlife of the United States. Nature Communications 2013, 4.
4. Loss, S.R.; Will, T.; Loss, S.S.; Marra, P.P. Bird-Building Collisions in the United States: Estimates of Annual Mortality and Species Vulnerability. The Condor 2014, 116, 8–23, doi:10.1650/CONDOR-13-090.1.
5. Loss, S.; Will, T.; Marra, P. Estimation of Bird-Vehicle Collision Mortality on U.S. Roads. The Journal of Wildlife Management 2014, 78, 763–771, doi:10.1002/jwmg.721.
6. Loss, S.R.; Will, T.; Marra, P.P. Refining Estimates of Bird Collision and Electrocution Mortality at Power Lines in the United States. PLOS ONE 2014, 9, e101565, doi:10.1371/journal.pone.0101565.
7. Loss, S.R.; Will, T.; Marra, P.P. Estimates of Bird Collision Mortality at Wind Facilities in the Contiguous United States. Biological Conservation 2013, 168, 201–209, doi:10.1016/j.biocon.2013.10.007.
8. Smallwood, K.S.; Bell, D.A.; Standish, S. Dogs Detect Larger Wind Energy Effects on Bats and Birds. The Journal of Wildlife Management 2020, 84, 852–864, doi:10.1002/jwmg.21863.
9. Klem, D., Jr.; Saenger, P.G.; Brogle, B.P. Evidence, Consequences, and Angle of Strike of Bird–Window Collisions. The Wilson Journal of Ornithology 2024, 136, 113–119, doi:10.1676/23-00045.
10. NABCI The State of the Birds, United States of America, 2022; North American Bird Conservation Initiative., 2022.

1. The studies used to derive these mortality estimates suggest that roughly 25% of mortalities are nestlings or juveniles; even so, an estimate of 3 billion mortalities is still nearly impossible to reconcile with bird population estimates. ︎
2. It’s worth noting that the mortality estimates attributable to collisions with buildings, vehicles, and power lines seem to include all 50 states and are therefore not directly comparable. ︎
3. Of course, this accounting still does not include other well-known sources of mortality, such as pesticides or habitat loss [10]. ︎
4. So eager to jump on the story that reporters couldn’t be bothered to ask even the most obvious question: How many birds are there? ︎

—Cat Wars: The Devastating Consequences of a Cuddly Killer

Hunters using 12-gauge shotguns killed 809 cats over three “hunting seasons” in 1986–1989 (photo by Kevin Language).

Roughly the size of Tampa, Florida, or Salt Lake City, Utah, Marion Island lies approximately 1,325 miles southeast of Cape Town, in the Indian Ocean. It is the largest island from which cats have been successfully eradicated, a campaign spanning more than 19 years during which an estimated 4,000–5,000 cats were killed. No cat has been seen there since July 1991 [1].

Nearly 33 years later, plans are underway for a new eradication campaign—this time to exterminate the island’s mice.

According to recent news accounts (warning: graphic images), the mice, whose numbers increased dramatically after the cats were exterminated, are literally eating seabirds alive. As a result, seabird recovery hasn’t been nearly as successful as had been hoped [2–4].

So, how did we get here? It wasn’t easy.

During the second phase of the seven-phase campaign, for example, the disease panleukopenia was introduced as this was deemed to be “the most efficient and cost-effective method” for quickly bringing down the island’s cat population [5].

“From July 1975, cats, which up to this point had been live trapped and then killed to obtain samples and measurements, were held captive in custom-made cages on the island to serve as future carriers for the establishment of the disease” [1].

It’s estimated that nearly 2,800 cats were killed over a five-year span from panleukopenia alone [5].

During the final phase of the campaign, 30,000 day-old chicken carcasses were injected with the toxin sodium fluoroacetate and distributed across the island [6].

Despite all the reports associated with the eradication campaign, little has been published regarding its economic costs. The only report I’ve found that mentions cost at all refers vaguely to “millions” having been spent during the first six phases with “more millions” required for the “the final, and most expensive, seventh phase” [4].

And eradication of the mice is expected to cost more than $20 million [4].

Given all this, it’s hardly surprising that TNR opponents never mention Marion Island. Pressed for an alternative, they instead resort to the vague arm waving, clumsy euphemisms, and tired dog whistles we’re all familiar with. Marion Island’s 19-year slog—quite literally, the removal of “all free-ranging cats from the landscape by any means necessary” [7]—is the best example they can point to.

Literature Cited

1. Bester, M.N.; Bloomer, J.P.; van Aarde, R.J.; Erasmus, B.H.; van Rensburg, P.J.J.; Skinner, J.D.; Howell, P.G.; Naude, T.W. A Review of the Successful Eradication of Feral Cats from Sub-Antarctic Marion Island, Southern Indian Ocean. South African Journal of Wildlife Research 2002, 32, 65–73.
2. Dilley, B.J.; Schramm, M.; Ryan, P.G. Modest Increases in Densities of Burrow-Nesting Petrels Following the Removal of Cats (Felis Catus) from Marion Island. Polar Biology 2017, 40, 625–637, doi:10.1007/s00300-016-1985-z.
3. Preston, G.R.; Dilley, B.J.; Cooper, J.; Beaumont, J.; Chauke, L.F.; Chown, S.L.; Devanunthan, N.; Dopolo, M.; Fikizolo, L.; Heine, J.; et al. South Africa Works towards Eradicating Introduced House Mice from Sub-Antarctic Marion Island: The Largest Island yet Attempted for Mice. In Island invasives: Scaling up to meet the challenge: Proceedings of the international conference on island invasives; Veitch, C.R., Clout, M.N., Martin, A.R., Russell, J.C., West, C.J., Eds.; IUCN: Gland, Switzerland, 2019; pp. 40–46.
4. Huntley, B.J. Marion Island: Birds, Cats, Mice and Men. In Strategic Opportunism: What Works in Africa : Twelve Fundamentals for Conservation Success; Huntley, B.J., Ed.; Springer Nature Switzerland: Cham, 2023; pp. 21–37 ISBN 978-3-031-24880-1.
5. Bloomer, J.P.; Bester, M.N. Control of Feral Cats on Sub-Antarctic Marion Island, Indian Ocean. Biological Conservation 1992, 60, 211–219.
6. Bester, M.N.; Bloomer, J.P.; Bartlett, P.A.; Muller, D.D.; Van Rooyen, M.; Buchner, H. Final Eradication of Feral Cats from Sub-Antarctic Marion Island, Southern Indian Ocean. South African Journal of Wildlife Research 2000, 30, 53–57.
7. Marra, P.P.; Santella, C. Cat Wars: The Devastating Consequences of a Cuddly Killer; Princeton University Press: Princeton, N.J., 2016; ISBN 978-0-691-16741-1.

His article in the most recent issue of The New Yorker suggests that those other forms of life do not include cats. In Franzen’s telling, cats, however affectionate they might be at times, “have a savage side as well, sharp of tooth and keen of claw,” and a “penchant for disembowelling wildlife.” Worse, they’re “non-native”—simply not a part of Franzen’s “natural world.”

This is nothing new for Franzen, a long-time member of ABC’s board, who’s gone out of his way to vilify cats for years now. In fact, the New Yorker piece is little more than a rehashing of the usual talking points deployed by the conservation community and PETA’s better-off-dead evangelists (for whom Franzen narrated a graphic PSA earlier this year).

TNR “doesn’t work”?

Check. (It’s “a strategy with no firm basis in science,” and “the handful of studies reporting success with TNR have been seriously flawed in one or more ways.”)

Cats as murderous super-predators?

Check. (Not only “sharp of tooth and keen of claw,” but more than likely having a “negative effect on American ecosystems.”)

Community cats as public health threat?

Check. (Cats “represent a significant source of human exposure” to rabies, and “fleas were a suspected vector in one of several typhus deaths reported in [Los Angeles] in 2022.”)

Community cats in poor health?

Check. (“A tabby with a huge tumor-like growth on its side. Two sway-backed, deformed looking cats.”)

Expressed empathy for community cats?

Check. (“The cats were skittish and hungry, endearing. It wasn’t their fault that they were on the street.”)

Exaggerated community cat numbers?

Check. (Neighborhoods “overrun with cats.”)

Comparison to hoarding?

Check. (“Feeder-breeders… are effectively outdoor-cat hoarders, akin to the people who hoard cats in their dwellings.”)

Xenophobic dog whistles?

Check. (As “non-native predatory species,” cats are “depriving native predators of meals they might have had.”)

On and on it goes, for more than 8,500 words.

SUSPENSION OF DISBELIEF

It’s not difficult to understand how Franzen got so much of this so wrong, given his sources. Take those public health threats, for example. “Rabies is relatively rare in cats,” explains Franzen, “but more cats than dogs are infected with it, and they represent a significant source of human exposure.”

While it’s true that more cats than dogs test positive for the virus (216 cats vs. 36 dogs during 2021, the most recent year for which data are available [2]), CDC reports challenge the idea that cats are a “significant source of human exposure.” Indeed, the last time a cat transmitted rabies to a human in this country was 1975 [3]. Since that time, 26 cases have been attributed to dogs (mostly among military personnel serving overseas), 32 cases have been attributed to wildlife, and another 54 to unknown causes (many of which are assumed to be associated with bat bites, which can be difficult to detect).

That leaves seven cases, all traced to arterial and organ transplants [4]. Again, there was just one instance of transmission from a cat over this same period.

And what about the risk of typhus? “Flea-borne typhus has been steeply on the rise in Los Angeles,” writes Franzen, “and cat fleas were a suspected vector in one of several typhus deaths reported in the city in 2022.”

Again, a CDC reports provides some important context, painting a rather different picture. During 2022, there were three deaths related to flea-borne typhus in all of Los Angeles County (population 9.8 million). And before 2022, “the most recent flea-borne typhus-associated death in [the county] was reported in 1993” [5]. The report notes that, in the case of one patient, “potential flea exposure included stray kittens living in the patient’s backyard.” However, “all three patients had comorbidities that might have placed them at increased risk for severe disease” [5].

I guess it makes for a better story the way Franzen tells it.

He takes a similar approach to the impact of predation. Franzen notes—correctly—that some of us “point to studies that have shown that birds killed by cats are less fit, on average, than birds killed in other ways, such as collisions with buildings.” He then goes on to hypothesize that perhaps “birds killed by cats are less fit because they were already stressed from living near them” (likely a reference to a dubious 2013 study of blackbird parents).

The problem with Franzen’s hypothesis is the empirical evidence to the contrary.

The studies in question used sampling techniques to ensure, as much as possible, that the birds examined came from the same population [6,7]. There’s simply no evidence that those killed in collisions with buildings or cars were any different in terms of their proximity to cats. And a similar pattern has been observed among other predator-prey dynamics [8,9].

Why this is such a tough pill to swallow is a mystery. Those of us who grew up watching Wild Kingdom learned that predators tend to catch “less fit” individuals. This is Predation 101.

JONATHAN FRANZEN’S BIG IDEA

So, what should we go about outdoor cats? Owned cats should be kept indoors, argues Franzen. To “humanely reduce the unowned-cat population,” though, is tricker:

“It might include TNR, provided that the cats are registered, microchipped for identification, and released to safe and confined locations. Since TNR will never be enough, there would also need to be ongoing efforts to remove cats from the environment, partly through adoption, partly through placement in sanctuaries, and partly through euthanasia.”

Again, more of the same tired talking points we’ve heard for years. There’s nothing new or different—or even interesting here. There’s no reason to think registration and microchipping would contribute to reduced community cat numbers. If anything, registration is likely to backfire, deterring caregivers from participating in TNR programs. And Franzen’s vague reference to “safe and confined locations” seems like nothing more than a feel-good way of distracting us from all the “euthanasia” he’s got in mind.

Even die-hard TNR opponent Peter Marra recognized the futility of sanctuaries, at least on any large scale [10]. Which leaves TNR, adoption, and, of course, “euthanasia”—a combination that describes the current situation in communities across the country. If that were effective, wouldn’t we know by now?

References

1. Lebbin, D.J.; Parr, M.J.; Fenwick, G.H. The American Bird Conservancy Guide to Bird Conservation; University of Chicago Press: London, 2010; ISBN 0-226-64727-7.
2. Ma, X.; Bonaparte, S.; Corbett, P.; Orciari, L.A.; Gigante, C.M.; Kirby, J.D.; Chipman, R.B.; Fehlner-Gardiner, C.; Thang, C.; Cedillo, V.G.; et al. Rabies Surveillance in the United States during 2021. J Am Vet Med Assoc 2023, 1–9, doi:10.2460/javma.23.02.0081.
3. Sung, J.H.; Hayano, M.; Okagaki, T.; Mastri, A. A Case of Human Rabies and Ultrastructure of the Negri Body. Journal of Neuropathology & Experimental Neurology 1976, 35, 541–559.
4. Dyer, J.L.; Yager, P.; Orciari, L.; Greenberg, L.; Wallace, R.; Hanlon, C.A.; Blanton, J.D. Rabies Surveillance in the United States during 2013. Journal of the American Veterinary Medical Association 2014, 245, 1111–1123.
5. Alarcón, J.; Sanosyan, A.; Contreras, Z.A.; Ngo, V.P.; Carpenter, A.; Hacker, J.K.; Probert, W.S.; Terashita, D.; Balter, S.; Halai, U.-A. Fleaborne Typhus–Associated Deaths — Los Angeles County, California, 2022. MMWR Morb. Mortal. Wkly. Rep. 2023, 72, 838–843, doi:10.15585/mmwr.mm7231a1.
6. Møller, A.P.; Erritzøe, J. Predation against Birds with Low Immunocompetence. Oecologia 2000, 122, 500–504, doi:10.1007/s004420050972.
7. Baker, P.J.; Molony, S.E.; Stone, E.; Cuthill, I.C.; Harris, S. Cats about Town: Is Predation by Free-Ranging Pet Cats Felis Catus Likely to Affect Urban Bird Populations? Ibis 2008, 150, 86–99, doi:10.1111/j.1474-919X.2008.00836.x.
8. Møller, A.P.; Nielsen, J.T. Genetic Variation in Birds in Relation to Predation Risk by Hawks: A Comparative Analysis. Current Zoology 2015, 61, 1–9, doi:10.1093/czoolo/61.1.1.
9. Temple, S.A. Do Predators Always Capture Substandard Individuals Disproportionately from Prey Populations? Ecology 1987, 68, 669–674, doi:10.2307/1938472.
10. Marra, P.P.; Santella, C. Cat Wars: The Devastating Consequences of a Cuddly Killer; Princeton University Press: Princeton, N.J., 2016; ISBN 978-0-691-16741-1.

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.

References

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.

This story falls into the latter category.

Using a network of wildlife cameras at 15 locations across Stillwater, Oklahoma, graduate student Seraiah Coe and her colleagues identified individual cats over a five-year period. At the end of the study period, they reported that the number of cats they could identify had dropped from 47 to 35 cats (a 25.5 percent reduction) or, “after correcting for detectability,” from 62 cats to 48 cats (a 22.6 percent reduction). Nevertheless, their statistical analysis found the decrease to be insignificant, leading the authors to conclude that “TNR conducted at its current intensity is unlikely to reduce Stillwater’s cat population… add[ing] further evidence to the growing body of scientific literature indicating that TNR is ineffective in reducing cat populations” [1].

In fact, their results are pretty impressive. To produce such results and then insist that they show TNR to be ineffective betrays a rather profound ignorance about the practice of TNR.

Sure, Coe and her co-authors found the reduction of cats to be statistically insignificant—but that probably has more to do with their choice of statistical tools than anything else. As it happens, their results compare quite favorably with what some very sophisticated computer modeling has predicted. Those results show that sterilizing 40 percent of the intact population every six months reduced the population from 200 to 169 cats (15.5 percent) in five years [2].

And, as with an earlier study the authors used as a baseline for their five-year-follow-up [3], no kittens were observed at any of the camera locations. This is Oklahoma in April—and no kittens.

Contrary to what Coe and her co-authors suggest, then, their results provide considerable support for TNR’s effectiveness across a large geographical area. And yet, they go out of their way to suggest just the opposite. How does this happen?

BLISSFUL IGNORANCE I

Coe and her authors observed that 6 of 35 cats they identified were ear-tipped, leading them to calculate a sterilization rate of 17.1 percent. This is based on the dubious assumptions that (1) all cats lacking collars and ear-tips are unsterilized community cats, and (2) only cats wearing collars (8 of 35 in this case) are owned. But a 2009 survey of Oklahoma City spay-neuter facilities and veterinary hospitals found that only 12 percent of cats brought to such clinics were wearing collars, and owners reported that only 11 percent of their cats always wore collars [4].

All of which will come as no surprise to anybody familiar with TNR. Or cat ownership, for that matter. After all, how many indoor-outdoor cats wear collars?

If the results from that 2009 survey are comparable to collar-wearing rates in Stillwater 10 years later, then it’s entirely possible that every one of the 21 cats identified by Coe and her co-authors without a collar or ear-tip was in fact owned—in which case, the true sterilization rate for community cats was 100 percent.* It’s likely, too, that a significant portion of the owned cats were also sterilized. Indeed, this would help explain the fact that no kittens were spotted at the 15 camera stations—despite there being no ear-tipped cats five years earlier [3].

BLISSFUL IGNORANCE II

There are a lot of holes in this study—the result being conclusions that simply aren’t supported by its findings. Again—how does this happen?

Well, three of the four authors were students at the time of the research—but I don’t think that explains it. The most likely explanation has to do with the fourth co-author, Scott Loss, in whose lab all three students have worked. This is the same Scott Loss whose flawed mortality estimates received so much media attention in 2013 (and have been cited frequently ever since).

The same Scott Loss who—along with frequent collaborator and Cat Wars author Peter Marra—has dismissed any research finding TNR to be effective (including my own) as “organized misinformation [that] has clouded consensus and misled policies affecting human health and biodiversity conservation” [5].

The same Scott Loss who’s complained repeatedly of the “population impacts” caused by free-roaming cats—while providing very little in the way of evidence [see, for example, 6,7].

So, how does a study demonstrating some pretty impressive results of community-wide TNR efforts become “further evidence to the growing body of scientific literature indicating that TNR is ineffective in reducing cat populations” [1]? Well, I can’t be certain—but I’ve got a pretty good idea.

*Admittedly, there is a complicating factor: Stillwater’s municipal code requires cats to wear collars and rabies tags. I don’t know that this explains the authors’ assumption, though, as there is no mention of it in either their paper or the one describing the baseline study. And I have no idea what such a provision would do for compliance—I suspect many cat owners have no idea such a law even exists. In any case, I can’t imagine the law drives compliance to the 100 percent level apparently assumed by Coe and her co-authors.

References

1. Coe, S.T.; Elmore, J.A.; Elizondo, E.C.; Loss, S.R. Free-Ranging Domestic Cat Abundance and Sterilization Percentage Following Five Years of a Trap–Neuter–Return Program. Wildlife Biology 2021, 2021, doi:10.2981/wlb.00799.
2. Miller, P.S.; Boone, J.D.; Briggs, J.R.; Lawler, D.F.; Levy, J.K.; Nutter, F.B.; Slater, M.; Zawistowski, S. Simulating Free-Roaming Cat Population Management Options in Open Demographic Environments. PLOS ONE 2014, 9, e113553, doi:10.1371/journal.pone.0113553.
3. Elizondo, E.C.; Loss, S.R. Using Trail Cameras to Estimate Free-Ranging Domestic Cat Abundance in Urban Areas. Wildlife Biology 2016, 22, 246–252, doi:10.2981/wlb.00237.
4. Slater, M.; Weiss, E.; Lord, L. Current Use of and Attitudes towards Identification in Cats and Dogs in Veterinary Clinics in Oklahoma City, USA. Animal Welfare 2012, 21, 51–57.
5. Loss, S.R.; Marra, P.P. Merchants of Doubt in the Free‐ranging Cat Conflict. Conservation Biology 2018, 32, 265–266, doi:10.1111/cobi.13085.
6. Loss, S.R.; Marra, P.P. Population Impacts of Free‐ranging Domestic Cats on Mainland Vertebrates. Frontiers in Ecology and the Environment 2017, 15, 502–509, doi:10.1002/fee.1633.
7. Loss, S.R.; Will, T.; Marra, P.P. The Impact of Free-Ranging Domestic Cats on Wildlife of the United States. Nature Communications 2013, 4.

A careful look at the authors’ analysis, though, raises serious doubts about their sweeping conclusions.

Home range estimates

In developing their “cat exclusionary buffer zones around urban forests,” Herrera et al. rely heavily on previous research (which has its own issues) documenting the home range of pet cats. They argue that using only average home range is insufficient, since, “in urban areas, many native species are found beyond the borders of green spaces… and variation in cat roaming behavior can be substantial” [1]. So instead, they use “the upper estimate of the average home range size of an urban cat” from a previous study: 0.092 square km, or about 22.7 acres [2].

It’s important to note that distributions of home range data are highly skewed (as illustrated in the figure below, taken from the very study Herrera et al. relied on for their analysis). For this reason, it’s much more appropriate to use the median rather than the mean, since the mean significantly over-estimates how far the “average” cat roams. This is readily apparent in Figure 2(a): the average is 0.036 square km—but approximately 488 of the 875 cats tracked (55.8%) had home ranges on the order of 0.025 square km. The median is more like 0.02 square km.

From Kays et al. [2]

This is a relatively minor discrepancy, however, in light of the fact that Herrera et al. studied cats in Washington, DC. The home range data they relied on from Kays et al. [2] included lots of cats from rural areas as well, where cats roam farther—sometime much farther [see 3 for a summary]. Indeed, the dataset used by Kays et al. included very few cats from areas as densely populated as Washington, DC.

Herrera claim that they used “the upper estimate of the average home range size of an urban cat” for their analysis, but this is incorrect. The number they used is the upper end of an average of both rural and urban cats—including very few who were “as urban” as those in the District. Again, it’s well known that cats in densely populated areas roam less. And sterilized cats tend to roam less than intact cats do [2]. Even in more rural areas, well-managed community cats typically stick close to “home.” For her PhD work, Felicia Nutter monitored cats in Randolph County, NC, for several years, concluding: “The home ranges of the managed feral cats were small, usually less than 1 hectare [the equivalent of 0.01 square km, or 2.5 acres], regardless of sex or reproductive status… the sizes of intact and castrated male cat home ranges were similar, as were the home ranges of intact and spayed female cats” [4].

Here’s why this matters: the larger an urban cat’s home range, the more likely they’ll encounter natural areas. This is especially true in a place like Washington, DC, which is a patchwork of “disturbed” areas and natural areas (e.g., dense residential areas adjacent to parks). Make the home range large enough, and the whole place is a no-go zone. Indeed, this is precisely what Herrera et al. conclude:

“The near-zero probability that a cat preys upon a native species… would require excluding cats from 91.7% of the study area” [1].

Not surprisingly, they don’t go into details about what this would entail.

TNR cats and feeding locations

Herrera et al. [1] seem to suggest that community cats are even more of a problem than other outdoor cats: “The total number of cat predation events at a site was best predicted by a cat’s prior participation in a TNR program… and local feeding location density.” Perhaps I’m missing something, but it seems like they’re overlooking an obvious point: there are generally more TNR cats in areas with more cats overall—and those parts of a community tend to be in densely populated urban areas, further from natural areas.

In addition, the authors note: “our analyses reveal that predation by cats is greatest where supplemental food is most abundant,” and therefore recommend that “management policies explicitly consider the spatial location of cat-feeding sites” [1]. Again, I might be missing something, but if predation “is greatest where supplemental food is most abundant,” that’s probably because that’s where the cats are. And, of course, the feeding is a response to the presence of cats. So, building on the previous point, (1) the TNR cats are where the rest of the cats are, and (2) all the cats are where the food is.

The claim that predation “is greatest where supplemental food is most abundant,” contradicts the findings of an earlier study led by co-author Michael Cove. In that study, conducted in the Florida Keys, Cove and his co-authors [5] reported that cats living farther away from human settlements (e.g., more than 1.9 miles) were more likely to prey on wildlife, and that more than 81% of the free-roaming cats tested “consumed mostly anthropogenic foods.”

In other words, the predation was greatest where supplemental food was least abundant. These findings correspond reasonably well with those of a study in Chile, where researchers concluded that “underfed” cats are nearly five times as likely to prey on wildlife, compared to adequately fed cats [6]. In fact, Herrera et al. [1] documented remarkably little predation overall: just 75 instances in 33,134 observations of cats (0.23%).

Although Cove’s earlier study is referred to repeatedly by Herrera et al. [1], the authors never acknowledge these important findings from the earlier study. Instead, they argue that, because “predation by cats is greatest where supplemental food is most abundant… management policies [should] explicitly consider the spatial location of cat-feeding sites.”

Native and non-native species

Herrera et al. [1] place a great deal of emphasis on the apparent risk to native species. However, their own research documented predation of just six different native species across eight (presumed) predation events:

• white-footed mouse (3)
• eastern gray squirrel (1)
• southern flying squirrel (1)
• Northern cardinal (1)
• mourning dove (1)
• yellow-throated warbler (1)

By comparison, three non-native species were documented across 44 (presumed) predation events:

• brown rat (34)
• house mouse (9)
• European starling (1)

To draw any meaningful conclusions on such a small sample is at best questionable.

If one can accept the small sample size, then why not focus on the fact that non-native species were predated at a rate of more than seven times that of native species? Readers could be forgiven for missing this point, given how little attention the authors give it.

It’s worth pointing out that all of the native species identified are common ones, too. The mourning dove, for example, is, according to the International Union for Conservation of Nature, “common across the continent and generally have prospered as people settled the landscape,” although “populations declined by about 15% between 1966 and 2015, according to the North American Breeding Bird Survey.” The Northern cardinal is “abundant in eastern and central North America… their numbers have increased by an estimated 0.32% per year since 1966.” And the yellow-throated warbler population has “increased by 50% between 1966 and 2014.” This species “appear[s]to be expanding northward and are recovering from population losses at the northern edge of their range in southern Michigan and northern Ohio, the causes of which are unknown.”

The fact that these species are common would seem to be an important point, but the authors seem more interested in focusing on their “nativeness.” (The native/non-native classification seems more useful for scaremongering and demonstrating tribal allegiance than for any legitimate conservation work, but that’s another conversation.)

Herrera et al. [1] acknowledge that “cats are opportunistic generalists, and their prey composition is generally proportionate to local prey availability,” but fail to consider the implications of this. Even the paper’s title—“prey selection” implies a preference for native species. I’m unaware of any cats using DoorDash or Uber Eats to have their preferred prey delivered; if cats caught more native prey near natural areas, it’s because the prey was both nearby and plentiful. Sweeping claims about the risk these cats pose to native species—presumably all of them—are simply not supported by the evidence presented.

Literature Cited

1. Herrera, D.J.; Cove, M.V.; McShea, W.J.; Flockhart, D.T.; Decker, S.; Moore, S.M.; Gallo, T. Prey Selection and Predation Behavior of Free-Roaming Domestic Cats (Felis Catus) in an Urban Ecosystem: Implications for Urban Cat Management. Biological Conservation 2022, 268, 109503, doi:10.1016/j.biocon.2022.109503.
2. Kays, R.; Dunn, R.R.; Parsons, A.W.; McDonald, B.; Perkins, T.; Powers, S.A.; Shell, L.; McDonald, J.L.; Cole, H.; Kikillus, H.; et al. The Small Home Ranges and Large Local Ecological Impacts of Pet Cats. Animal Conservation 2020, n/a, doi:10.1111/acv.12563.
3. Liberg, O.; Sandell, M.; Pontier, D.; Natoli, E. Density, Spatial Organisation and Reproductive Tactics in the Domestic Cat and Other Felids. In The Domestic Cat: The biology of its behaviour; Turner, D.C., Bateson, P.P.G., Eds.; Cambridge University Press: Cambridge, 2000; pp. 119–147.
4. Nutter, F.B. Evaluation of a Trap-Neuter-Return Management Program for Feral Cat Colonies: Population Dynamics, Home Ranges, and Potentially Zoonotic Diseases, North Carolina State University: Raleigh, NC, 2005.
5. Cove, M.V.; Gardner, B.; Simons, T.R.; Kays, R.; O’Connell, A.F. Free-Ranging Domestic Cats (Felis Catus) on Public Lands: Estimating Density, Activity, and Diet in the Florida Keys. Biological Invasions 2018, 20, 333–344, doi:10.1007/s10530-017-1534-x.
6. Silva-Rodríguez, E.A.; Sieving, K.E. Influence of Care of Domestic Carnivores on Their Predation on Vertebrates. Conservation Biology 2011, 25, 808–815, doi:10.1111/j.1523-1739.2011.01690.x.

For whatever reason, I don’t see this element included in news stories anymore. It’s not because caregivers have stopped naming cats, though—I’m sure of that much. Such frequent, close interactions also allow caregivers to track the regulars, identify newcomers, and note disappearances. As a caregiver myself, I find this ability—to provide a reasonably accurate count of the cats we see regularly, often on a daily basis—rather unremarkable.

For some TNR opponents, though, there is simply no way that such counts can be trusted. After all, they argue, most of us lack the training to provide accurate and reliable population estimates. This is apparently what it’s come to: faced with empirical evidence that poses a direct threat to their dogmatic belief that “TNR doesn’t work,” these people have begun to dispute our ability to count cats.

In Cat Wars: The Devastating Consequences of a Cuddly Killer, for example, longtime TNR opponent Peter Marra complains about the methods used for a 1991–2002 study conducted on the University of Central Florida campus.

“The Levy et al. report [1] includes only one brief mention of a census of the colony, in 1996, and it includes no details of how the count was done. Counting free-ranging cats is notoriously difficult; for a study aimed at examining the impact of TNR on the numbers of outdoor cats, the absence of details on census procedures suggests a first serious flaw… Levy and colleagues do not explain how or when the cats were counted, so it is not clear how reliable any of these figures actually are” [2].

In fact, the study in question provided considerably more detail than Marra suggests.

“Beginning in 1991, volunteers began an organized effort to capture free-roaming cats on campus for neutering and to keep records of cat sightings and human interventions. Additional colonies were added to the control program as they were discovered. Cats were recorded as kittens if they were believed to be ≤6 months of age. Cats were classified as feral if they avoided human contact… By 1996, all cats on campus were identified and cataloged, including photographs and written descriptions of each cat, socialization status (feral vs. socialized), colony affiliations, and final outcomes. Data from the daily observation logs were condensed into quarterly reports” [1, emphasis added].

Obviously, the people involved with this campus TNR program were (as is typically the case with such programs) far more involved than would be required of a one-time annual census. That much is clear from reading the paper. And if Marra had any questions, he could have reached out to those involved—as Dan Spehar did a few years ago, to gather updated census data for a study he and I had published in 2019. What we learned expanded on what had been reported earlier, both in terms of documented population reductions (spanning 28 years) and detailed tracking information.

“Cats were recorded and their presence tracked as they were discovered on the UCF campus. Each cat was assigned a name and tracked by colony affiliation on a Microsoft Excel spreadsheet. The enrollment date, description (as well as a photograph), sex, age category (adult or kitten), perceived level of socialization at first appearance (socialized or feral), date neutered/neuter status, departure date (if applicable), and final outcome (if applicable) for each cat was documented” [3].

The reliability question raised by Marra seems to betray a profound ignorance of TNR at its most basic level. Or perhaps it merely betrays a desperate attempt to discredit the methods used to document its efficacy—in the face of mounting evidence. Of course, the two aren’t mutually exclusive.

Unfortunately, this question-that’s-not-a-question continues to come up. In 2020, Mark Hostetler and four colleagues in the Department of Wildlife Ecology and Conservation at the University of Florida’s Institute of Food and Agricultural Sciences Extension, charged down the same path in their publication, “How Effective and Humane Is Trap-Neuter-Release (TNR) for Feral Cats?,” questioning the accuracy of population estimates associated with TNR studies (including the one cited by Marra).

“Many of the above studies (e.g., [1,4]) were conducted with volunteers and used surveys of caretakers or veterinary clinic records to estimate abundance. These studies did not use standardized field observations; thus, results are likely not accurate” [5].

It’s difficult to imagine how daily interactions with cats aren’t every bit as valid as “standardized field observations,” but again, the authors don’t seem to understand TNR at its most basic level. Nevertheless, Hostetler and his colleagues continue:

“To highlight the discrepancy in data collection, we present data from a study where only one caretaker surveyed cats at various feeding stations in Key Largo from 1999 to 2013 [6]. This caretaker did not report how often each feeding station was sampled. The number of feeders changed from year to year, and many of the feeding stations were located near each other, so that cats very likely ate from multiple stations, yet the caretaker provided no rationale for how double counting was avoided” [5].

Once again, the study in question provides more detail than is suggested here. Kreisler et al. note, for example, that “the status of MIA was assigned to cats that had not been sighted at their usual feeding station for an unusual period of time, as determined by the caretaker” [6, emphasis added]. And although the authors acknowledge that “multiple population census methods would have been ideal, as caretakers may underestimate the number of cats,” they also note that the caregiver responsible for the censuses “was highly knowledgeable of the entire population, which she interacted with on a daily basis.” Moreover, “20 cats were added to census estimates by the caretaker to account for potential undercounting. The small size of each colony, particularly in later years, should also have made count estimates more accurate” [6, emphasis added].

I contacted Hostetler with several questions, pointing out that caretakers typically know each cat in their care, observe the cats daily, and can provide a significant level of detail for tracking them over time. “We absolutely do not agree that caretakers of TNR colonies can give reliable estimates,” he responded, “as they have not been trained on population ecology field protocols.”

Again, such protests suggest that Hostetler and his colleagues lack a basic understanding of TNR or are simply determined to undermine such programs. Or both. In fact, the authors reveal something important about their analysis by accepting at face value nuisance complaint data “measured indirectly and… based on citizens’ description and not on objective measures” [7].

In other words, the real test of any data is whether it can be used to throw the cats under the bus. This is exactly what Hostetler and his colleagues are trying to do, as can be seen in their 2019 op-ed for The Gainesville Sun (co-authored by the American Bird Conservancy’s Grant Sizemore):

“We (the authors) love cats and hope more funding is directed towards prevention; we maintain, based on the best available science, that TNR is not a viable solution. Overall, we view TNR strategies as inhumane to the cats themselves and potentially dangerous to humans, pets and wildlife.”

Not surprisingly, the authors fail to acknowledge that TNR is, in fact, the best “prevention” available. And—again, not surprisingly—they offer nothing in the way of an alternative to TNR— though, of course, readers familiar with the topic can certainly read between the lines.

University of Georgia graduate student Heather Gaya, however, has been more direct. In a comment responding to a December 15 post on Project Bay Cat’s Facebook page, Gaya, too, challenged the validity of caregivers’ population estimates, suggesting that the alternatives to TNR are adoption or “TNE” (presumably trap-neuter-euthanize). TNR? “Maybe not.”

Like Marra and Hostetler, Gaya—who “really enjoys cats”—justifies her opposition to TNR in part by attempting to discredit well-documented population reductions. Referring to a study published last year,* documenting a reduction from 175 cats to just one over 16 years [8], she is incredulous:

“I want to believe in this study but there are some alarming issues with their data collection and results that make me hesitant to accept the study at face value. It’s clear nobody on the paper is a wildlife statistician—they inappropriately use the word ‘population census’ (ouch) and their population estimate process in their methods is shaky. Just because you don’t see cats doesn’t mean the cat population isn’t there.”

“I’m glad those cats were fixed and aren’t out and about causing issues,” Gaya continues, “but it doesn’t mean TNR is the answer.” Never mind the fact that her “answer” has been the default approach for managing free-roaming cats in the U.S. for generations now [9]. And, just like the TNR studies cited here, you don’t need to be a “wildlife statistician” to interpret the results.

*In the interest of full disclosure, this is another one of the studies I’ve co-authored with Dan Spehar.

Literature Cited

1. Levy, J.K.; Gale, D.W.; Gale, L.A. Evaluation of the Effect of a Long-Term Trap-Neuter-Return and Adoption Program on a Free-Roaming Cat Population. Journal of the American Veterinary Medical Association 2003, 222, 42–46, doi:10.2460/javma.2003.222.42.
2. Marra, P.P.; Santella, C. Cat Wars: The Devastating Consequences of a Cuddly Killer; Princeton University Press: Princeton, N.J., 2016;
3. Spehar, D.D.; Wolf, P.J. Back to School: An Updated Evaluation of the Effectiveness of a Long-Term Trap-Neuter-Return Program on a University’s Free-Roaming Cat Population. Animals 2019, 9.
4. Centonze, L.A.; Levy, J.K. Characteristics of Free-Roaming Cats and Their Caretakers. Journal of the American Veterinary Medical Association 2002, 220, 1627–1633, doi:10.2460/javma.2002.220.1627.
5. Hostetler, M.; Wisely, S.M.; Johnson, S.; Pienaar, E.F.; Main, M. How Effective and Humane Is Trap-Neuter-Release (TNR) for Feral Cats?; University of Florida, Institute of Food and Agricultural Sciences Extension, 2020;
6. Kreisler, R.E.; Cornell, H.N.; Levy, J.K. Decrease in Population and Increase in Welfare of Community Cats in a Twenty-Three Year Trap-Neuter-Return Program in Key Largo, FL: The ORCAT Program. Frontiers in Veterinary Science 2019, 6, doi:10.3389/fvets.2019.00007.
7. Gunther, I.; Raz, T.; Berke, O.; Klement, E. Nuisances and Welfare of Free-Roaming Cats in Urban Settings and Their Association with Cat Reproduction. Preventive veterinary medicine 2015, 119, 203–210, doi:10.1016/j.prevetmed.2015.02.012.
8. Spehar, D.D.; Wolf, P.J. The Impact of Targeted Trap–Neuter–Return Efforts in the San Francisco Bay Area. Animals 2020, 10, doi:10.3390/ani10112089.
9. Wolf, P.J.; Hamilton, F. Managing Free-Roaming Cats in U.S. Cities: An Object Lesson in Public Policy and Citizen Action. Journal of Urban Affairs 2020, 1–22, doi:10.1080/07352166.2020.1742577.

“I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.” —Abraham Maslow

Just three months after an intensive culling effort, conservationists observed no difference in the area’s population of cats. Nevertheless, they describe their campaign as “effective,” arguing that lethal methods could be improved only if they were more “intense and continuous.”

Non-lethal methods, it seems, never occurred to them.

The campaign was conducted on a small peninsula, roughly 10 square miles in size, on the New Caledonian island of Grande Terre, approximately 880 miles northeast of Brisbane, Australia. Over the course of 38 days, researchers deployed 32 traps daily across an area slightly more than four square miles, capturing and then killing 36 cats [1]. In their recently published study documenting the project, the researchers describe the cull as “effective” since it resulted in the removal of “an estimated 44% of the population” (based on camera trap data).

And yet…

“Three months after the end of the culling campaign that eliminated 36 cats… no meaningful differences in the relative abundance and density of feral cats were observed in response to culling, whatever the indicator of population size considered” [1].

If this is what “effective” looks like, one wonders what it would take for these researchers to admit failure.

This is not the first study of its kind. Research from Tasmania, published in 2015, also employed camera traps to estimate cat numbers before and after lethal removal. Following that campaign, which the researchers describe as “low-level culling,” the “minimum number of feral cats known to be alive” increased—an average of 75 percent at one site and 211 percent at another [2].

Here, too, the researchers emphasized the need for “intensity of [lethal] effort” over any consideration of non-lethal methods.

Not surprisingly, the obvious implications of the Tasmanian study have been almost entirely ignored by TNR opponents. And there’s no reason to think the findings of the New Caledonian study will be treated any differently. After all, if removing nearly half the cats from a four-square-mile peninsula makes no difference in their numbers three months later, what hope is there that such a campaign—requiring far more effort than even a well-resourced animal control agency can afford—would make a difference where cats are far more abundant (e.g., urban and suburban areas of the U.S. [3])?

Instead, opponents are likely to continue arguing—despite mounting evidence to the contrary—that “TNR doesn’t work” [4–8], and implying that lethal removal does—again, despite mounting evidence to the contrary. This, too, should come as no surprise. If they were to acknowledge the numerous failures of lethal methods, across a range of environmental contexts, their argument house of cards would quickly collapse.

Literature Cited

1. Palmas, P.; Gouyet, R.; Oedin, M.; Millon, A.; Cassan, J.-J.; Kowi, J.; Bonnaud, E.; Vidal, E. Rapid Recolonisation of Feral Cats Following Intensive Culling in a Semi-Isolated Context. NB 2020, 63, 177–200, doi:10.3897/neobiota.63.58005.
2. Lazenby, B.T.; Mooney, N.J.; Dickman, C.R. Effects of Low-Level Culling of Feral Cats in Open Populations: A Case Study from the Forests of Southern Tasmania. Wildlife Research 2015, 41, 407–420.
3. Rowan, A.N.; Kartal, T.; Hadidian, J. Cat Demographics & Impact on Wildlife in the USA, the UK, Australia and New Zealand: Facts and Values. Journal of Applied Animal Ethics Research 2019.
4. Longcore, T.; Rich, C.; Sullivan, L.M. Critical Assessment of Claims Regarding Management of Feral Cats by Trap-Neuter-Return. Conservation Biology 2009, 23, 887–894.
5. Marra, P.P.; Santella, C. Cat Wars: The Devastating Consequences of a Cuddly Killer; Princeton University Press: Princeton, N.J., 2016;
6. Gerhold, R.W.; Jessup, D.A. Zoonotic Diseases Associated with Free-Roaming Cats. Zoonoses and Public Health 2012, 60, 189–195, doi:10.1111/j.1863-2378.2012.01522.x.
7. Lepczyk, C.A.; Lohr, C.A.; Duffy, D.C. A Review of Cat Behavior in Relation to Disease Risk and Management Options. Applied Animal Behaviour Science 2015, 173, 29–39, doi:10.1016/j.applanim.2015.07.002.
8. Crawford, H.M.; Calver, M.C.; Fleming, P.A. A Case of Letting the Cat out of The Bag—Why Trap-Neuter-Return Is Not an Ethical Solution for Stray Cat (Felis Catus) Management. Animals 2019, 9, doi:10.3390/ani9040171.

Violet-green swallow (Tachycineta thalassina). Photo courtesy of Alan Vernon and Wikimedia Commons

Following their investigation into the cause of the mysterious migratory songbird deaths in New Mexico last fall, the U.S. Geological Survey National Wildlife Health Center has concluded that the primary culprit was starvation. According to a December 4 media release from the New Mexico Department of Game and Fish, “the lab report indicates that the single abnormality shared by nearly all birds was body condition ranging from poor to severely emaciated.”

What’s this got to do with cats? Nothing, really.

It is curious, though—the evidence used by U.S.G.S. to come to their conclusion is remarkably similar to that used years ago to argue that birds killed by cats were, on average, less healthy than those killed in collisions with buildings and vehicles. And that evidence has been dismissed out of hand by longtime TNR opponents. All of which raises some obvious questions.

In their media release, the New Mexico Department of Game and Fish described the U.S.G.S. analysis, listing specific findings indicative of “physical exertion without nourishment to support recovery, including:

• the large breast muscles controlling birds’ wings were severely shrunken;
• kidney failure was apparent in many of the birds;
• stomachs and intestines were empty of foodstuffs;
• many intestines contained small amounts of blood, which is one of the effects of starvation;
• fat deposits, the stored energy for migration, were depleted; and
• lung tissues were irritated.”

These findings correspond well with those from an earlier analysis examining the condition of 258 violet-green swallows collected in Velarde, New Mexico, following the mysterious September mortality event. Writing for the American Birding Association’s website, University of New Mexico Ph.D. candidate Jenna McCullough explains that she and her colleagues found that the average weight of the Velarde swallows “was dramatically lighter” than expected. In addition, “of the hundreds of birds… assessed, none had fat stores on their bodies. Furthermore, many birds also showed signs of breast muscle atrophy, which points to starvation and dehydration.”

Twelve years earlier, in the U.K., Philip Baker and his co-authors conducted a similar analysis of 134 birds, 86 of which had been killed by pet cats. The other 48 had been “killed by a collision accident, e.g., with a window or car” [1]. “Across species,” the authors reported, “birds killed by cats had significantly lower mass, fat scores and pectoral muscle mass scores.”

Although Baker et al. cautioned that “the relationship between body mass and quality (i.e., likelihood of long-term survival and therefore reproductive potential) in passerines is complex,” they nevertheless concluded that “the mean fat scores evident in the cat-killed birds in [their] study were sufficiently low that these individuals were likely to have had poor long-term survival prospects” [1, emphasis added]. Indeed, this would seem to the case, given the massive mortality event in and around New Mexico last September.

And yet, TNR opponents Scott Loss, Tom Will, Travis Longcore, and Peter Marra have rejected such analyses, arguing that such “crude” methods provide no “evidence that the birds killed [by cats] would have lower fitness or survival” [2].

Admittedly, it sounds like the U.S.G.S. analysis was more extensive than what Baker et al. conducted. Still, the similarities—the low body weight and minimal fat reserves, as well as the atrophied pectoral muscles—are hard to ignore. And it’s difficult to imagine that such findings could explain how migrating birds in poor condition, faced with an early winter storm, literally fell from the sky—yet tell us nothing about how such birds are more easily caught by cats.

Apparently, though, this is exactly what Loss, Will, Longcore, and Marra would have us believe.

Literature Cited

1. Baker, P. J., Molony, S. E., Stone, E., Cuthill, I. C., & Harris, S. (2008). Cats about town: Is predation by free-ranging pet cats Felis catus likely to affect urban bird populations? Ibis, 150, 86–99. https://doi.org/10.1111/j.1474-919X.2008.00836.x
2. Loss, S. R., Will, T., Longcore, T., & Marra, P. P. (2018). Responding to misinformation and criticisms regarding United States cat predation estimates. Biological Invasions, 20(12), 3385–3396. https://doi.org/10.1007/s10530-018-1796-y

Seven months later, the non-profit appealed to OIA for nearly a quarter-million dollars more, this time to “remove” cats from Palau’s Ulong Island. One would expect such a request to be a detailed account explaining, among other things, why, before even getting underway, their original project had so expanded in its scope as to justify a budget twice the size of the original.

Apparently, though, such rigor is unnecessary—perhaps even unwelcome—at OIA. Instead, a little creativity seems to be the key to winning over the agency’s decision-makers. Less than one month after receiving the request, the agency awarded Island Conservation $239,922 “to eradicate feral cats in the Ulong Island area of the Rock Islands Southern Lagoon.”

After briefly thanking OIA for funding their project to “remove” rats, authors of the Island Conservation proposal got to the point of their follow-up: “During preliminary research for this project, we identified that feral cats are also present at the site.”

“Consequently, we are seeking further support from the OIA to ensure full restoration of Ulong Island. Removal of rats alone will not permit full recovery of ecosystem services and protection of endemic and threatened species. Only the removal of both invasive species will generate the sought‐after improvements to reef health and human livelihoods that this project promises to deliver.”

There’s good evidence to show that removing either rats or cats is unlikely to protect island seabirds [1–3]. Still, Island Conservation’s follow-up request raises a number of questions. How well did they survey the island before submitting the first proposal, for example, if the presence of cats later came as a surprise? After all, Ulong appears to be no more than about nine square miles. And if no cats were detected during the initial survey, how many can there really be on an island this size?

Island Conservation’s proposal (obtained via public records request* and available as a PDF here) for eradicating cats includes a number of sweeping claims with little or no support. “In Palau,” reads one section, “feral cats are widespread and impact biodiversity, disturb ecosystem services, reduce the availability of natural resources, and spread diseases such as toxoplasmosis.” Like so much of the proposal, the justification for more killing is little more than arm-waving.

What the proposal lacks in specificity, though, it makes up for in creativity. In what might be a first in the ongoing campaign to kill cats, there’s this: “the feral cat problem in Palau has recently been in the spotlight with feral cats having been reported stealing food from rural communities.”

Other claims of alleged impacts are less creative, perhaps, but a stretch nonetheless.

“The impacts of both cats and rats on Ulong have resulted in a massive decline in the island’s seabird populations, disrupting the critical function that former bird colonies played in bringing nutrients from sea to land. In turn, this will have impacted adjacent coral reefs by removing an essential nutrient subsidy. Consequently, the site is not meeting its full potential as a tourist destination nor are subsistence fishers able to reap the rewards of a healthy coral reef.”

So, cats are to blame for declining seabird numbers and the poor health of the area’s coral reefs—all of which threatens tourism and subsistence fishing? The only supporting evidence provided by Island Conservation is a reference to a 2007 report from the Palau National Environmental Protection Council.

“According to the Palau National Invasive Species Strategy (2007), rats, feral cats, macaques, smothering vines, snails, algae, agricultural pests, and pathogens have invaded Palau, impacted the environment, the economy, human health, and even the traditional Palauan way of life.”

In fact, the report itself mentions cats only once, in defining “feral animals.” The section Island Conservation was apparently referring to reads somewhat differently.

“Monkeys, cockatoos, smothering vines, snails, aggressive fish, bottom-dwelling marine organisms, agricultural pests, and human disease-causing microorganisms: all of these and more have invaded Palau, and all are having impacts on the environment, the economy, human health, and even the traditional Palauan way of life” [4].

Perhaps the authors of Island Conservation’s proposal thought it prudent to give the rats and cats top billing, thereby highlighting the need for the organization’s (ever-expanding) services.

Threat assessment

As the authors of Island Conservation’s proposal note, climate change poses a significant threat to Palau’s coral reefs. However, the same 2017 NEPC report cited to support this claim is rather unambiguous about the current state of the reefs: “Palau’s coral reefs—the basis for much of the economy—are largely in good condition” with the exception of the “outer reefs on the East Coast,” which “are in poor condition following two Supertyphoons” [5]

Reading Island Conservation’s proposal, of course, one comes away with a very different impression—of both the overall condition of the areas coral reefs and the reason for recent damage. In addition, the threats suggested by Island Conservation are not among those cited as “pressures and threats” by NEPC: “overfishing, sedimentation from land, and the daily cumulative plus long-term impacts of climate change” [5].

And what about those “massive declines” in seabird populations? One would expect such a claim to be supported with at least a couple citations, yet none is provided. Nothing about declining seabirds and nothing about the cause being cats and rats. I’ve been unable to locate any predation studies of conducted on Ulong Island, or in Palau more generally. Moreover, a study published just last month found that the number of endangered Micronesian scrubfowl observed on Ulong was significantly greater than estimates from four nearby islands popular with tourists (just like Ulong), more closely resembling observations from nearby islands not visited by tourists [6].

To be clear: this was not a predation study and the scrubfowl are not seabirds. Even so, if the island’s cats (and rats) are truly responsible for “massive declines” in its seabird population, one would expect some mention of this threat in such a detailed survey of the island. Instead—in an interesting twist—the study’s authors highlight a different threat: “tourism activities and facilities” might be adversely affecting scrubfowl breeding and “augmenting rodent populations through supplementary food provision” [6].

This, of course, raises a question that goes to the very heart of Island Conservation’s proposal: Is “meeting its full potential as a tourist destination” really good for Ulong’s plant and animal life? (Of course, taking such questions seriously might jeopardize support for the project from local stakeholders heavily reliant on tourism.)

A lack of creativity when it’s most needed

Unfortunately, the Island Conservation team’s creativity ran out before they identified their intended method of “removal.” Their budget includes $2,500 for “high‐powered air rifle, case, and accessories for the humane removal of feral cats”—even though previous, well-documented eradication campaigns have demonstrated the relative ineffectiveness of shooting cats [7–9].

(As an aside—it strikes me as odd that an organization so deeply involved in eradication efforts actually requires more rifles—or footwear and backpacks, also included in the budget—but these discrepancies are in keeping with the rest of the proposal.)

No doubt, there will be additional requests for funding from Island Conservation. As the organization notes in its proposal, “The UNESCO‐designated [Rock Island Southern Lagoon] is a logical starting point to cultivate invasive species management skills in Palau and demonstrate the feasibility of eradicating feral cats from islands” (emphasis mine).

Many thanks to Jodie LoMeli for bringing this story to my attention.

*Island Conservation did not respond to my request for a copy of their proposal.

Literature Cited

1. Courchamp, F.; Langlais, M.; Sugihara, G. Cats protecting birds: modelling the mesopredator release effect. Journal of Animal Ecology 1999, 68, 282–292.
2. Fan, M.; Kuang, Y.; Feng, Z. Cats protecting birds revisited. Bulletin of Mathematical Biology 2005, 67, 1081–1106.
3. Gambino, J.; Martínez-Martínez, M.V.; Salau, K.; Soho, E.L.; Hiebeler, D.E.; S⬚ánchez, F.; Murillo, D. Cats Protecting Birds Revisited with a Spatial Approach.; 2007.
4. NEPC Palau National Invasive Species Strategy; Palau National Environmental Protection Council, 2007;
5. NEPC 2017 State of the Environment Report Republic of Palau; Palau National Environmental Protection Council, 2017;
6. Radley, P.M.; Davis, R.A.; Doherty, T.S. Impacts of invasive rats and tourism on a threatened island bird: the Palau Micronesian Scrubfowl. Bird Conservation International 2020, 1–13, doi:10.1017/S0959270920000246.
7. Bester, M.N.; Bloomer, J.P.; Aarde, R.J. van; Erasmus, B.H.; Rensburg, P.J.J. van; Skinner, J.D.; Howell, P.G.; Naude, T.W. A review of the successful eradication of feral cats from sub-Antarctic Marion Island, Southern Indian Ocean. South African Journal of Wildlife Research 2002, 32, 65–73.
8. Veitch, C.R. The eradication of feral cats (Felis catus) from Little Barrier Island, New Zealand. New Zealand Journal of Zoology 2001, 28, 1–12.
9. Campbell, K.J.; Harper, G.; Algar, D.; Hanson, C.C.; Keitt, B.S.; Robinson, S. Review of feral cat eradications on islands. In Island invasives: eradication and management; Veitch, C.R., Clout, M.N., Towns, D.R., Eds.; IUCN: Gland, Switzerland, 2011; pp. 37–46.