The Sister Islands Rock Iguana is native to only two small enclaves on our planet: Cayman Brac and Little Cayman, the lesser populated of the three Cayman Islands, which are generally more famous for its corporate tax havens than rare lizards.
Now numbering below 2,000 according to the Cayman National Trust, the gray-green, 40-inch long creatures are imperiled by danger from every direction: road traffic, human development, and other animals, including a rival common green iguana, subject to a previous bloodbath in 2019 and on course for another soon.
More recently, the Cayman government has been reviving a controversial plan that it says could address the lizards’ dwindling numbers: exterminating the local stray cat population. The reasoning is that, while the adult lizards are large enough to fend off interested felines, hatchlings and young iguanas are easy prey.
The government has already made several efforts, including caging the endangered lizards, establishing an “Iguana hotline” to report casualties, and even building an ‘E-Guana' app to monitor the creatures. In 2017, armed with transmitters, cameras, and other equipment, the Cayman Department of Agriculture and the Department of Environment monitored the hatchlings of these reptiles in order to determine just who or what was to blame for the declining population.
Although only two of the 28 deployed transmitters were confirmed to be cat-related kills, according to a Cayman government FAQ, given the large number of cats on Little Cayman, many more iguanas could have fallen victim to the felines. When it was decided that the survival of these iguanas was at a crisis point, the government devised a plan: they would kill some of the cats.
In 2018, the extermination plan was about to get underway until two local charities, Feline Friends and the Cayman Islands Humane Society, caught wind of the initiative and obtained a court injunction to put a halt to the project.
Rather than slaughtering the cats, the charities hoped that a “Trap, Neuter, Vaccinate, Release” (TNVR) programme would be possible instead—a self-explanatory approach where cats are captured and then put back into the wild, but unable to breed—arguing it would be both more effective and humane than the government’s original plans to lay poisons.
This year, the injunction was lifted, and the charities have settled in order to recoup their CI$25,000 (US$30,000) costs.
The debate is a contentious one, pitting conservation and animal welfare groups against each other, as they argue over the effectiveness and ethics of killing versus neutering and spaying.
Conservationists say that TNVR programs are not impactful or quick enough in a time of crisis, such as when extinction is threatened. But animal welfare groups say that if animals are killed and not neutered, the culled populations can recover—or even increase—leaving conservationists with lots of dead animals but little in the way of results. Full-on eradication programmes are, they argue, inhumane and rarely ethically justifiable, especially when they're ineffective.
One of the most commonly cited statistics is that cats globally kill up to 22 billion animals a year, which comes from a meta analysis conducted as part of a paper by Cat Wars author Pete Marra, published in Nature Communications in 2013. Conservationists like Marra believe the cat problem has become so extreme that mass feline bloodshed may be the only way forward to protect birds. Critics have pushed back against Marra’s claims, though, saying the statistics in his paper were exaggerated, flawed, dangerous, and have negatively impacted compassionate conservation. The US Humane Society said the true number is unknowable, while advocacy groups like Alley Cat Allies claimed the research was cherry-picked to reach its conclusion.
Some vocal bird enthusiasts, like Marra, say cullings are a necessary evil to curb the natural predatory instinct of the global feline population. But others say the situation in the Caymans is all merely the latest attempt to vilify the domestic cat—an easy scapegoat, and a distraction from the well-documented human impact on environmental devastation.
While cat advocacy groups acknowledge that felines can have a negative impact on their surroundings, they also say eradication programmes often have unintended consequences and may not be particularly effective in the first place. An increasing number are pushing back against the notion that cats are the destructive force to blame for declining biodiversity, like with the Sister Islands Rock Iguana.
On Little Cayman, the government’s plan will begin with the microchipping of “companion cats” on the small island. Next, authorities will lay traps across Little Cayman, and any cats found in them without one of these microchips will be euthanized by a vet. The project will begin with a limited culling, although the government is also investigating the feasibility of island-wide eradication.
Part of the ominously titled “Darwin Plus” initiative, a British government scheme to protect biodiversity, the Cayman project is funded by a £484,227 ($585,972) grant from the UK’s environment department, Defra. Since 2012, Darwin Plus has awarded £32 million to projects in UK Overseas Territories—self-governing territories with historical ties to the UK that still count the British monarch as their official head of state. So it’s perhaps fitting that leading the project in partnership with the Cayman government and a local university will be the Royal Society for the Protection of Birds (RSPB), whose royal charter was granted by King Edward VII in 1904, crusading today against the cats of Little Cayman.
To the outside observer, conservation may occasionally look like a morbid trolley problem meme, where some groups invested in the protection of a species strive to have another culled. The RSPB, in its contract application for the Cayman project, boasts of its grisly success in eradicating cats from other areas like the Turks & Caicos islands.
An RSPB spokesperson, though, told Motherboard that its involvement in this project was based on years of government monitoring in the Sister Islands. The government’s studies “showed dramatic population declines in the unique and critically endangered sister islands rock iguana population, with feral cats identified as the primary driver” from camera-trap images and community feedback, the spokesperson said.
The spokesperson said they didn’t consider TNVR schemes an “effective mechanism for removal of a non-native invasive species when a rapid response to a conservation issue is required.”
A spokesperson for the Ministry of Sustainability & Climate Resiliency declined to comment. Defra also did not respond.
Some residents have been vocal about their support for the cull over the years, posting bloodthirsty comments such as “Lock and Load!” on government Facebook pages, which have frequently reposted the same image of a cat carrying an iguana in its mouth.
But not all local residents are as trigger-happy.
“I believe they’re not looking at the bigger picture,” said a Cayman resident who has tracked the project and did not want to be named. They said that while cats may have been responsible for some of the iguana deaths, the “development on this island is just going and going and going”.
Another resident, who requested anonymity due to their residency status, told Motherboard: “I believe the assumption that feral cats are to blame is largely erroneous, but even if we accept that to be the case, I think the solution should be to make sure they’re spayed and neutered.”
The first resident added that they believed a previous cull in 2019—where 320 licensed cullers were registered to remove the common green iguana population, removing 825,420 iguanas for a total bounty of approximately $4.5 million—may have had inadequate controls over the kinds of iguanas that were being destroyed, and that, anecdotally speaking, it’s rare now to see any type of iguana at all. “With all the construction, they have nowhere to go,” the resident added. “To be honest, a lot of us do not believe it’s going to make a difference.”
Indeed, the IUCN Red List, which categorizes endangered species, notes that the exact impact and extent of mortality by cat predation is “extremely difficult to establish” because rock iguana hatchlings are tricky to observe, and the high levels of cat kills are largely assumed based on the number of cats on the island.
But it also notes that habitat loss, including a boom in road construction, commercial and residential real estate development in sensitive nesting areas are other leading causes. In 2010, about 10 percent of all rock iguana deaths were due to road vehicles. And, as the Territory’s National Trust notes, these creatures mainly congregate around the built-up areas of “Blossom Village,” one of the more developed sites on Little Cayman.
Bolivian Tree Lizards
The situation on Little Cayman brings to mind a 1998 episode of The Simpsons, where Principal Skinner attempts to decapitate a pair of invasive “Bolivian Tree Lizards” with a paper cutter. The cold-blooded duo are rescued at the final hour, unleashing a plague of reptiles on Springfield and subsequently destroying the troublesome local pigeon population. But, asks Lisa, what happens when we’re overrun by lizards? No problem, replies Skinner: we “simply unleash wave after wave of Chinese Needle Snakes”—and after them, an injection of gorillas to deal with the newfound snake problem. Conveniently, he says, “When wintertime rolls around, the gorillas simply freeze to death.”
It’s a comedic exaggeration of the human impact of intervening in nature—with good intentions or not. But these kinds of domino effects can and do happen.
Take Isla Isabel, a densely forested tropical island near Puerto Vallarta on Mexico’s Pacific Coast. Here, cats and rats were preying on ground-nesting seabirds, some of which were driven into threatened status. But after a successful cat eradication program, the rats there “bred like mad”, which then further threatened the birds. When the rats were subsequently removed, the birds became even more threatened, because both the cats and the rats were controlling a native species of predatory snake that hadn’t been accounted for, which was now feasting on the eggs of those seabirds.
Then there’s Marion Island, roughly the size of Salt Lake City, the largest island where domestic cats have ever been eradicated. The campaign took place over 19 years, eradicating as many as 3,400 cats. Although seabird breeding may have increased soon afterwards, researchers also reported population recoveries of other species as either slower than anticipated or nonexistent because the island’s mouse population began to thrive. Now, 50 years after the island’s first cats were killed, a mouse extermination programme is being planned.
When cats were removed on Macquarie Island, in the Pacific Ocean, the rabbit population spiked dramatically, devastating local vegetation and threatening other species. And on Amsterdam Island in the Indian Ocean, killing cats resulted in a spike in the populations of rats and mice, subsequently harming the bird population.
The RSPB argues that there’s abundant scientific literature highlighting the impact of feral cats when they’re introduced out of their natural range, and that on islands, reports claim they’re responsible for at least 14 percent of global bird, mammal, and reptile extinctions. Some conservationists will also point to successful eradication programmes as one of the most effective tools for protecting wildlife.
But any perceived benefits around eradication are not so cut and dry, argues William Lynn, author of 2019 paper, A Moral Panic Over Cats and a research scientist and ethicist at the George Perkins Marsh Institute at Clark University.
“I’m not saying you can’t make good faith judgments about what’s invasive or not,” Lynn told Motherboard. “But you always have to do so in context; you can’t a priori claim cats are always a problem everywhere, you have to think about the site and the situation.”
Coryn Julien, director of communications at the cat advocacy group Alley Cat Allies, points to other factors that have led to environmental destruction. “Leading biologists, climate scientists and environmental watchdogs agree that climate change, habitat destruction and development are the leading causes of species loss,” Julien told Motherboard. "Attempting to pin the blame on cats conveniently ignores the reality that the solutions to species loss are squarely in our hands.”
More broadly, Julien says, “The idea that we must kill cats to save wildlife is both scientifically and morally flawed. Cats have been a part of ecosystems for thousands of years in many cases and removing them can destabilize the relationships between the different predator and prey species, with dire consequences.”
Less ambitious, limited cullings, such as the one starting on Little Cayman, may also prove Quixotic.
In 2015, a low-level ad hoc culling of feral cats proved ineffective at removing the numbers of cats in southern Tasmania—and may have actually increased as “less dominant” resident cats were removed, something known as the “vacuum effect.” Meanwhile, in New Caledonia, a 44 percent reduction in the cat population amounted to “no meaningful differences in the relative abundance and density of cats” three months later.
“In certain circumstances culling can be an effective tool to urgently prevent critical biodiversity loss, though we are exploring the feasibility of a feral cat eradication on Little Cayman as a more permanent solution,” said the RSPB spokesperson, although they did not elaborate.
But, “unless they’re committed to cullings in perpetuity, it’s a fool’s errand,” countered Lynn. “You have to constantly remove 70% of the cats from the landscape in order to reduce their population, and the reason for that is cats can have multiple litters over the years. So this isn't just an annual cull, so to speak, it's this constant process, and it has to be a very, very large number of cats.”
“And if cats are an invasive species, because they do damage, there is no more invasive species in the world than us,” Lynn added.
With the court injunction lifted, the Cayman Islands Humane Society seems resigned to the inevitable course of culling that the government has sought since 2018. It says that it is now playing a role in ensuring that the project is carried out legally, and as humanely as possible, and will advocate for spay and neuter programmes to become the default in the future.
“Spay and neuter as a method of population control option comes with significant resource costs and is a longer term sustainable approach that cannot of course solve an immediate population crisis,” Humane Society operations manager Samantha Cooper told Motherboard. “That said, our focus has to be on spaying and neutering as a long-term humane solution to the overpopulation issue. We do not want these cats to be destroyed, but in the absence of any viable alternative, we have worked hard to ensure that the programme is conducted lawfully and humanely.”
Time will tell if the Darwin Plus project effectively solves the island’s rock iguana problem. But Lynn asserts that there are more ethical and effective ways to reduce the damage cats do, in places where it’s been demonstrated conclusively that they are indeed the perpetrators.
On Hawaii’s Lanai Island, the outdoor cat population was moved into a sanctuary, while in the Channel Islands’ San Nicolas island, cats were moved to a sanctuary under an agreement with the US Navy, the Humane Society, and the California Fish & Wildlife service. In Amami Oshima Island in Japan, tourists were asked to cover the cost of non-lethal cat population management—and around 80% of visitors were happy to do so.
Peter Wolf, a research and policy analyst at the Best Friends Animal Society, thinks the Cayman Islands would be a suitable site for a targeted TNVR program, combined with relocation or containment. "Being a closed population is perhaps the most obvious advantage—it makes it that much easier to conduct a proper census of the cat and iguana populations, for example, and to track the impact of targeted sterilization efforts,” Wolf told Motherboard. "This knee-jerk reaction—to turn to eradication as a presumed solution—strikes me as a missed opportunity or at best, it reflects a lack of imagination."