Controlling invasive species helps Little Cayman flourish

(CNS): After a steep decline in the population of the unique and endangered Sister Islands rock iguana, they and other indigenous species are thriving again on Little Cayman due to the work done by the Department of Environment to control invasive species. The island was once an untouched haven for native species and virgin habitat, but over the last twenty years, it has suffered a loss of biodiversity resulting from an explosion in the population of feral cats.

After just two years of control work, about 87% of the cats have been removed from the natural environment, and residents have already noticed a significant increase in the number of young rock iguanas. Other native wildlife, including curly-tailed lizards, birds, butterflies and the endemic Little Cayman anole, are also flourishing.

The DoE recorded the cats’ consistent impact on biodiversity with cameras placed in the wild. That and iguana remains showed clear evidence of cat predation, particularly on hatchling, young, and sub-adult iguanas. However, it took years and numerous court battles for the control work to get underway due to opposition to culling the cats and a campaign by local charities to spay and neuter the animals.

However, such ‘trap and release’ projects would not have addressed the problem, which was reaching a critical situation for the unique species on Cayman’s smallest and least populated island.

The DoE partnered with the Royal Society for the Protection of Birds (RSPB) and the National Trust for the Cayman Islands and was supported by funding from the UK Darwin Plus. The department also has a legal mandate to control feral cat populations living in the wild.

In conjunction with the removal of feral cats, the DoE embarked on a campaign to promote responsible pet ownership in the community and develop biosecurity protocols with local stakeholders to help secure the Sister Islands from invasive species arriving undetected in cargo.

As well as being a threat to native species, the wild cats are suffering. Over the last two years, the DoE has studied the health of feral cats removed from the environment, and found that they were starving and plagued with injuries and infections. Many had mature parasites and trash in their stomachs, and the females were found to have had excessive pregnancies.

The work began to yield results within the first year of the control programme, the DoE said. In 2023, the department invited a team of invasive species eradication experts from Australia to visit Little Cayman. Having conducted a preliminary study on the feasibility of eradicating feral cats entirely from the island, the Australian experts found that this was possible.

Little Cayman’s small land mass and relatively low human population make the proposition feasible. However, similar work on other islands indicates that a variety of methods are needed to ensure its success.

The Australian team has returned this month to perform tests using non-lethal traps and non-toxic bait to determine if they might impact native species. Over the next four weeks, a non-lethal, humane, soft-clamp leg-hold trap and a suspended, non-toxic bait lure will be tested in the environment. However, the DoE explained in a release that these will not be armed or enabled, so the leg traps will not close, and the baits will be non-toxic.

“Motion cameras will record any species which interact with the setups so its safety and efficacy can be determined before any decisions to move forward with the project are made,” the release said.

“These deactivated testing traps are solely for the purpose of studying how Little Cayman’s native species will react to them and will help determine if iguanas, birds or land crabs, for example, are attracted to the non-toxic test bait to help inform adjustments if needed and ultimately, whether the techniques can work safely in Little Cayman’s ecosystem, illuminating harm to non-target species.”

The testing traps, which will be clearly marked, pose no threat to humans or pets.

At a public meeting on Little Cayman hosted by the DoE Terrestrial Resources Unit (TRU), residents indicated support for the preservation of the island’s endemic species, especially the rock iguana. They also said that eradicating feral cats would be a massive step towards biodiversity conservation in Little Cayman.

However, eradication or even extensive control over wide areas is not on the agenda for Grand Cayman or Cayman Brac as these areas are much more densely populated and complex, the release said. But depending on how the tests go, a new conversation with the community about the possibility of eradicating all feral cats from the delicate island ecosystem of Little Cayman will emerge.

“It is only with community support across the islands that our unique biodiversity might be preserved and protected from the impacts of invasive predators,” the DoE said.