Lethal removal of cats backfires (again)

“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.



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