Why Eradication Programs Do Not Work
Every day more and more sterilization programs or Trap-Neuter-Return (TNR) for feral cats are being implemented across the United States and around the world. Compassionate communities are embracing this humane, non-lethal method of managing community cats because it is effective. Unlike TNR programs which stabilize populations, improve the overall health of outdoor cats, and reduce both shelter costs and euthanasia rates, eradication programs (also known as Catch-and-Kill) are in effective, costly, and cruel. For decades animal control and wildlife services have been managing outdoor cat populations using lethal methods to no avail. In most cases, removing cats from a territory results in larger problems and ends up costing more money and time.
Difficult to determine success
Once an eradication program has started, it must continue until all targeted individuals have been killed in order to be successful. A primary weakness of eradication programs is that it is close to impossible to determine if all targeted subjects have been killed, let alone identified. When they are not identified nor killed, the breeding cycle will repopulate the area. Since individuals become trap-shy or immune to introduced disease, it becomes more difficult to kill the last few individuals. However, the killing cannot continue indefinitely and the program must cease at some point.
And an eradication program cannot just stop at any given time. A mistaken assumption that eradication is complete when it really isn’t, can have disastrous consequences: “the species can bounce back and even expand its range, causing environmental and economic damage, and rendering the initial eradication campaign redundant” (Rout et al., 2013).
The “vacuum effect”
History has shown that the Catch-and-Kill method does not effectively reduce feral cat populations. Killing is a temporary, quick fix that may appeal to authorities but it does not stop the breeding cycle. When cats are trapped and removed from an area, new cats quickly move in to fill the vacated territory and start the breeding process all over again. This phenomenon in cat groups was discovered by British biologist Roger Tabor and is referred to as the “vacuum effect” (Tabor, 1983). However, if a group of cats is “neutered and returned to its area it will continue to hold the location and keep other cats out by its presence” (Tabor, 1995). If new unsterilized cats are permitted to join the group, they will be sterilized and returned.
A perfect example of the vacuum effect is illustrated by a recent study conducted by Lazenby et al. (2015) in the forests of Tasmania, Australia. “Low-level culling of feral cats” actually caused an increase in the number of cats in the area, despite the initial illusion that there was a decrease in population. At the end of the study, researchers noted a significant increase in feral cat numbers with an average of 75% at one site and 211% at the other site.
Counterproductive
Eradication programs for feral cats can also be counterproductive with potentially catastrophic consequences on local ecosystems. After cats were eradicated from Macquarie Island, near Antarctica, the rat population exploded, decimating the ground-nesting bird populations (rats feed on eggs and baby birds) (Strickland, 2009). Rabbits, too, increased in population, which destroyed the island’s vegetation; this resulted in decreased materials for birds to build nests and left the native penguin population more susceptible to predators. Scientists spent 7 years eradicating the rats, mice, and rabbits to combat their increased predation on birds (Strickland, 2009; Australian Department of the Environment, 2009). And on Wake Atoll, part of the Pacific Islands, a U.S. military base eradicated the cat population (though a few cats have since been sighted), which allowed for the rat population to dramatically increase. The base continues to implement rat control measures (Rauzon et al., 2008).
In a letter to Nature, biologists Kevin R. Crooks and Michael E. Soulé explain that when large mammalian carnivores disappear (or in the case of eradication programs, they are lethally removed), this causes small carnivores, or mesopredators, to increase (Crooks and Soulé, 1999). In other words, when a top predator, such as the cat, is removed from the food chain, smaller predators like rats—along with prey animals like rabbits—increase in abundance, which is often bad news for an ecosystem.
Costly and very time-intensive
Eradicating feral cats is a futile endeavor that comes with a hefty price tag—at the expense of the taxpayer—and requires decades of continual killing. It took over 15 years and cost AU$2.5 million (about $2 million USD) to eradicate the 2,500 cats on Macquarie Island (which is only 21 miles long and 3 miles wide), with another AU$24 million (about $19.5 million USD) allocated to eradicating the rats and rabbits over 7 years (Veitch et al., 2011).
Marion Island near South Africa is only 15 miles long and 10 miles wide, yet it took 19 years to kill 3,400 cats (Bester et al., 2002). Additionally, it cost $1.3 billion to eradicate the cats living on Ascension Island (located in the South Atlantic Ocean), which is only 34 square miles (Veitch et al., 2011).
These eradication programs that are deemed “successful” within the scientific community have been carried out on small, isolated islands with little to no human inhabitants. Attempting to eradicate an entire population of feral cats on a continent, with far more variables and unpredictable outcomes would be futile.
Cruel and inhumane
Along with being ineffective and costly, eradication programs are also cruel and inhumane to the animals being culled. In most cases, the animals die slow, painful deaths due to asphyxiation, starvation, dehydration, dismemberment, or over-exposure to weather elements. Killing methods used for feral cats include poisoned bait, cage traps, leg-hold traps, shooting, gassing, drowning, hunting dogs, and deadly viruses. Some countries have even invented new ways of killing feral cats. In the above island examples, every eradication program required more than one method of killing to eliminate most or all of the feral cats.
Collateral damage
Eradication programs rarely kill only the one intended species; more often, many non-target animals are killed as well. Poisoned bait does not discriminate between a cat and another meat-eating animal, and intentionally unleashed viruses like FeLV infect feral cats and domestic cats alike. In these programs, when live-trapped cats show no sign of ownership (i.e., a collar or microchip) they are killed even if they are someone’s pet. On Ascension Island, 38 percent of domestic house cats were killed, causing “public consternation” (Ratcliffe et al., 2010).
In some cases, eradication of feral cats is done through secondary poisoning, meaning prey animals are intentionally poisoned in order to kill cats who eat the tainted prey. On the New Zealand island of Tuhua, cats were removed through secondary poisoning by attempting to eradicate two types of rats living on the island (Ratcliffe et al., 2010).
Perpetuates animal abuse
Implementing Catch-and-Kill to manage any animal population, not just cats, perpetuates the school of thought that animal cruelty is tolerable. When communities support lethal methods of control, it sends the public a message that it is morally acceptable to kill sentient beings. Humans created the situation that feral cats are currently in: we domesticated them, we relocated them to every corner of the Earth, and we allowed them to reproduce. Therefore, it is our responsibility to manage them humanely. Killing is the highest form of abuse; it is certainly not humane.
Feeding Bans
Coupled with Catch-and-Kill programs, some authorities enact feeding bans, blaming caregivers for perpetuating and even starting feral cat groups by feeding stray and feral cats. They think the cats can be “starved out,” so they implement feeding bans and threaten anyone caught feeding outside cats with fines and jail time. These plans never work because cats are territorial animals who won’t quickly abandon an area, and they are also very resourceful scavengers, finding new food sources even when supplies are scarce. In some cases, when residents are instructed to stop feeding, the cats will actually move closer to humans in search of food, not farther away.
In addition, compassionate people continue to feed outdoor cats regardless of potential fines and other repercussions. It’s a natural act for humans to feed an animal to keep him/her from starving. A recent study concluded that as much as 25% of U.S. households, approximately 30 million, are feeding at least 1 community cat (Lord, 2008).
Conclusion
The traditional method of controlling feral cats by catching and killing them is not only outdated but it has been proven ineffective, counterproductive, and costly. The few examples scientists like to provide of “successful” cat eradication programs took several years, millions of taxpayer dollars, and were carried out on tiny islands, most uninhabited by humans. Removing the cats in these examples also released prey populations of rats and rabbits, so eradication programs were implemented to remove those animals from the ecosystem as well. Even removing one species from an ecosystem can have catastrophic consequences, setting off a chain reaction that could result in the total collapse of that ecosystem. Once you start killing, you have to continue to kill until all targeted animals are removed or the breeding cycle will repopulate the area.
For more detailed information, see Chapter 5 of our Guide to Managing Community Cats.
References
Bester, M. N. et al. “A Review of the Successful Eradication of Feral Cats from Sub-Antarctic Marion Island, Southern Indian Ocean.” South African Journal of Wildlife Research 32.1 (2002): p–65. Print.
Crooks, Kevin R., and Michael E. Soulé. “Mesopredator Release and Avifaunal Extinctions in a Fragmented System.” Nature 400.6744 (1999): 563–66. www. Nature.com. Web. 1 July 2014.
Lazenby, Billie T., Nicholas J. Mooney, and Christopher R. Dickman. “Effects of Low-Level Culling of Feral Cats in Open Populations: A Case Study from the Forests of Southern Tasmania.” Wildlife Research 41.5 (2015): 407–20. Print.
Lord, Linda K. “Attitudes toward and Perceptions of Free-Roaming Cats among Individuals Living in Ohio.” Journal of the American Veterinary Medical Association 232.8 (2008): 1159–67. Avmajournals.avma.org (Atypon). Web. 16 Jan. 2015.
Ratcliffe, Norman et al. “The Eradication of Feral Cats from Ascension Island and Its Subsequent Recolonization by Seabirds.” Oryx 44.01 (2010): 20–29. Cambridge Journals Online. Web. 29 Sept. 2014.
Rout, T.M. et al. “When to Declare Successful Eradication of an Invasive Predator?” Animal Conservation (2013): 125–32. Web. 14 Nov. 2014.
Tabor, Roger K. The Wild Life of the Domestic Cat. London: Arrow Books, 1983. Print.
Veitch, C.R., M.N. Clout, and D.R. Towns, eds. “Island Invasives: Eradication and Management.” International Conference on Island Invasives. University of Auckland, New Zealand: International Union for Conservation of Nature and Natural Resources, 2011. 37–46. Prin
Difficult to determine success
Once an eradication program has started, it must continue until all targeted individuals have been killed in order to be successful. A primary weakness of eradication programs is that it is close to impossible to determine if all targeted subjects have been killed, let alone identified. When they are not identified nor killed, the breeding cycle will repopulate the area. Since individuals become trap-shy or immune to introduced disease, it becomes more difficult to kill the last few individuals. However, the killing cannot continue indefinitely and the program must cease at some point.
And an eradication program cannot just stop at any given time. A mistaken assumption that eradication is complete when it really isn’t, can have disastrous consequences: “the species can bounce back and even expand its range, causing environmental and economic damage, and rendering the initial eradication campaign redundant” (Rout et al., 2013).
The “vacuum effect”
History has shown that the Catch-and-Kill method does not effectively reduce feral cat populations. Killing is a temporary, quick fix that may appeal to authorities but it does not stop the breeding cycle. When cats are trapped and removed from an area, new cats quickly move in to fill the vacated territory and start the breeding process all over again. This phenomenon in cat groups was discovered by British biologist Roger Tabor and is referred to as the “vacuum effect” (Tabor, 1983). However, if a group of cats is “neutered and returned to its area it will continue to hold the location and keep other cats out by its presence” (Tabor, 1995). If new unsterilized cats are permitted to join the group, they will be sterilized and returned.
A perfect example of the vacuum effect is illustrated by a recent study conducted by Lazenby et al. (2015) in the forests of Tasmania, Australia. “Low-level culling of feral cats” actually caused an increase in the number of cats in the area, despite the initial illusion that there was a decrease in population. At the end of the study, researchers noted a significant increase in feral cat numbers with an average of 75% at one site and 211% at the other site.
Counterproductive
Eradication programs for feral cats can also be counterproductive with potentially catastrophic consequences on local ecosystems. After cats were eradicated from Macquarie Island, near Antarctica, the rat population exploded, decimating the ground-nesting bird populations (rats feed on eggs and baby birds) (Strickland, 2009). Rabbits, too, increased in population, which destroyed the island’s vegetation; this resulted in decreased materials for birds to build nests and left the native penguin population more susceptible to predators. Scientists spent 7 years eradicating the rats, mice, and rabbits to combat their increased predation on birds (Strickland, 2009; Australian Department of the Environment, 2009). And on Wake Atoll, part of the Pacific Islands, a U.S. military base eradicated the cat population (though a few cats have since been sighted), which allowed for the rat population to dramatically increase. The base continues to implement rat control measures (Rauzon et al., 2008).
In a letter to Nature, biologists Kevin R. Crooks and Michael E. Soulé explain that when large mammalian carnivores disappear (or in the case of eradication programs, they are lethally removed), this causes small carnivores, or mesopredators, to increase (Crooks and Soulé, 1999). In other words, when a top predator, such as the cat, is removed from the food chain, smaller predators like rats—along with prey animals like rabbits—increase in abundance, which is often bad news for an ecosystem.
Costly and very time-intensive
Eradicating feral cats is a futile endeavor that comes with a hefty price tag—at the expense of the taxpayer—and requires decades of continual killing. It took over 15 years and cost AU$2.5 million (about $2 million USD) to eradicate the 2,500 cats on Macquarie Island (which is only 21 miles long and 3 miles wide), with another AU$24 million (about $19.5 million USD) allocated to eradicating the rats and rabbits over 7 years (Veitch et al., 2011).
Marion Island near South Africa is only 15 miles long and 10 miles wide, yet it took 19 years to kill 3,400 cats (Bester et al., 2002). Additionally, it cost $1.3 billion to eradicate the cats living on Ascension Island (located in the South Atlantic Ocean), which is only 34 square miles (Veitch et al., 2011).
These eradication programs that are deemed “successful” within the scientific community have been carried out on small, isolated islands with little to no human inhabitants. Attempting to eradicate an entire population of feral cats on a continent, with far more variables and unpredictable outcomes would be futile.
Cruel and inhumane
Along with being ineffective and costly, eradication programs are also cruel and inhumane to the animals being culled. In most cases, the animals die slow, painful deaths due to asphyxiation, starvation, dehydration, dismemberment, or over-exposure to weather elements. Killing methods used for feral cats include poisoned bait, cage traps, leg-hold traps, shooting, gassing, drowning, hunting dogs, and deadly viruses. Some countries have even invented new ways of killing feral cats. In the above island examples, every eradication program required more than one method of killing to eliminate most or all of the feral cats.
Collateral damage
Eradication programs rarely kill only the one intended species; more often, many non-target animals are killed as well. Poisoned bait does not discriminate between a cat and another meat-eating animal, and intentionally unleashed viruses like FeLV infect feral cats and domestic cats alike. In these programs, when live-trapped cats show no sign of ownership (i.e., a collar or microchip) they are killed even if they are someone’s pet. On Ascension Island, 38 percent of domestic house cats were killed, causing “public consternation” (Ratcliffe et al., 2010).
In some cases, eradication of feral cats is done through secondary poisoning, meaning prey animals are intentionally poisoned in order to kill cats who eat the tainted prey. On the New Zealand island of Tuhua, cats were removed through secondary poisoning by attempting to eradicate two types of rats living on the island (Ratcliffe et al., 2010).
Perpetuates animal abuse
Implementing Catch-and-Kill to manage any animal population, not just cats, perpetuates the school of thought that animal cruelty is tolerable. When communities support lethal methods of control, it sends the public a message that it is morally acceptable to kill sentient beings. Humans created the situation that feral cats are currently in: we domesticated them, we relocated them to every corner of the Earth, and we allowed them to reproduce. Therefore, it is our responsibility to manage them humanely. Killing is the highest form of abuse; it is certainly not humane.
Feeding Bans
Coupled with Catch-and-Kill programs, some authorities enact feeding bans, blaming caregivers for perpetuating and even starting feral cat groups by feeding stray and feral cats. They think the cats can be “starved out,” so they implement feeding bans and threaten anyone caught feeding outside cats with fines and jail time. These plans never work because cats are territorial animals who won’t quickly abandon an area, and they are also very resourceful scavengers, finding new food sources even when supplies are scarce. In some cases, when residents are instructed to stop feeding, the cats will actually move closer to humans in search of food, not farther away.
In addition, compassionate people continue to feed outdoor cats regardless of potential fines and other repercussions. It’s a natural act for humans to feed an animal to keep him/her from starving. A recent study concluded that as much as 25% of U.S. households, approximately 30 million, are feeding at least 1 community cat (Lord, 2008).
Conclusion
The traditional method of controlling feral cats by catching and killing them is not only outdated but it has been proven ineffective, counterproductive, and costly. The few examples scientists like to provide of “successful” cat eradication programs took several years, millions of taxpayer dollars, and were carried out on tiny islands, most uninhabited by humans. Removing the cats in these examples also released prey populations of rats and rabbits, so eradication programs were implemented to remove those animals from the ecosystem as well. Even removing one species from an ecosystem can have catastrophic consequences, setting off a chain reaction that could result in the total collapse of that ecosystem. Once you start killing, you have to continue to kill until all targeted animals are removed or the breeding cycle will repopulate the area.
For more detailed information, see Chapter 5 of our Guide to Managing Community Cats.
References
Bester, M. N. et al. “A Review of the Successful Eradication of Feral Cats from Sub-Antarctic Marion Island, Southern Indian Ocean.” South African Journal of Wildlife Research 32.1 (2002): p–65. Print.
Crooks, Kevin R., and Michael E. Soulé. “Mesopredator Release and Avifaunal Extinctions in a Fragmented System.” Nature 400.6744 (1999): 563–66. www. Nature.com. Web. 1 July 2014.
Lazenby, Billie T., Nicholas J. Mooney, and Christopher R. Dickman. “Effects of Low-Level Culling of Feral Cats in Open Populations: A Case Study from the Forests of Southern Tasmania.” Wildlife Research 41.5 (2015): 407–20. Print.
Lord, Linda K. “Attitudes toward and Perceptions of Free-Roaming Cats among Individuals Living in Ohio.” Journal of the American Veterinary Medical Association 232.8 (2008): 1159–67. Avmajournals.avma.org (Atypon). Web. 16 Jan. 2015.
Ratcliffe, Norman et al. “The Eradication of Feral Cats from Ascension Island and Its Subsequent Recolonization by Seabirds.” Oryx 44.01 (2010): 20–29. Cambridge Journals Online. Web. 29 Sept. 2014.
Rout, T.M. et al. “When to Declare Successful Eradication of an Invasive Predator?” Animal Conservation (2013): 125–32. Web. 14 Nov. 2014.
Tabor, Roger K. The Wild Life of the Domestic Cat. London: Arrow Books, 1983. Print.
Veitch, C.R., M.N. Clout, and D.R. Towns, eds. “Island Invasives: Eradication and Management.” International Conference on Island Invasives. University of Auckland, New Zealand: International Union for Conservation of Nature and Natural Resources, 2011. 37–46. Prin