Evidence of impacts of invasive species on native wildlife
What is an invasive species?
An alien species is when an animal or plant has been taken by humans and introduced into an ecosystem where it is not naturally present. An alien species becomes classified as an invasive species when it can reproduce and proliferate in the ecosystem, causing negative changes.
This is different to a native species that naturally live and thrive in a particular ecosystem having evolved there over millions of years.
Invasive species are incredibly problematic and can quickly take over a habitat disrupting the natural functions and balance of that ecosystem. This can affect the useful services provided by the ecosystem such as pollinating crops, seed dispersal, oxygen and moisture production and water filtration to name a few. Sometimes an invasive species can become so numerous it is a public health or road safety hazard.
Why are feral cats a problem in the Cayman Islands?
Cats are kept as domestic pets, however large numbers of unowned feral cats are present across all three islands in both urban and remote natural habitats. Cats have an innate instinct to hunt prey, whether intended as a food source or not. The Cayman Islands are small island ecosystems where there are no natural predators, so native wildlife did not evolve to have instincts against these cunning hunters. Many of Cayman’s native species are experiencing dramatic declines in population numbers as a result of being hunted by roaming cats.
Globally, roaming cats have contributed to the extinction of at least 33 species and continue to threaten other critically endangered species where they have been introduced, including in the Cayman Islands.
The Grand Cayman Blue Iguana and Sister Islands Rock Iguana are directly threatened with extinction by feral cats. Iguanas are vulnerable to predation within the first two years of life, and population data from surveys show young iguanas are becoming rarer to find, with too few iguanas making it to breeding age. Seabirds nesting in the Cayman Islands are also directly threatened with local extinction by feral cats. Sometimes an entire seabird family has been destroyed by cats, as the parents try to defend the flightless chicks.