The gentle purr of a domestic cat often evokes comfort, a stark contrast to the profound ecological disruption these animals can cause. Across the globe, both house cats and feral cats have emerged as a significant threat to global biodiversity. Their predatory instincts, when unleashed in vulnerable ecosystems, have contributed to a devastating toll on wildlife. This impact is particularly evident in the extinction of at least 33 species of birds, mammals, and reptiles linked to domestic and feral cats.
The Extinction Toll
A 2016 study published in the Proceedings of the National Academy of Sciences (PNAS) highlighted the severe impact of invasive predators, including cats, on global biodiversity. This research points to free-ranging cats on islands as having caused or contributed to the extinction of at least 33 endemic vertebrate species recorded on the International Union for Conservation of Nature (IUCN) Red List. These extinctions represent a portion of the broader impact of invasive mammalian predators, which are implicated in 58% of all modern bird, mammal, and reptile extinctions worldwide.
Birds comprise a substantial number of the lost species. Examples include the Guadalupe storm petrel from the Pacific coast of Mexico, and island bird species like the Townsend’s shearwater, Socorro dove, and Marquesan ground dove, all affected by cat predation. Mammals have also suffered losses, with Caribbean hutias among the species driven to extinction by introduced cat populations. Reptiles have also experienced extinctions due to feline predation on islands.
The Island Effect
The majority of cat-driven extinctions have occurred in island ecosystems, which are uniquely susceptible to new predators. Island species often evolve in isolation, without ground predators, leading to “island tameness” or “ecological naivete.” Native island animals frequently lack defensive behaviors against mammals, making them highly vulnerable to efficient hunters like cats. Their populations are often small and geographically restricted, limiting their ability to recover from sudden predation pressure.
The extinction of the Stephens Island Wren (Traversia lyalli), a small, flightless bird endemic to Stephens Island, New Zealand, illustrates this vulnerability. Discovered in 1894, this ground-dwelling wren had evolved without mammalian predators and was unable to escape the cats introduced by lighthouse keepers. While often attributed to a single cat, a growing population of feral cats, established by 1894, rapidly increased and devastated the wren population, leading to its extinction within a few years, possibly by 1895 or shortly thereafter. The flightless nature of the wren, combined with its confinement to a small, isolated habitat, made it particularly susceptible to the new predatory threat.
Mechanisms of Feline Predation
Cats possess innate biological traits that make them highly effective predators. Their stealthy movements, acute senses of hearing and sight, and natural agility allow them to stalk and ambush prey with remarkable success. This predatory drive is deeply ingrained in their DNA, stemming from their evolutionary history as hunters. Their instinct to hunt persists even when well-fed by their owners, meaning domestic cats can still prey on wildlife despite not relying on it for sustenance.
This “surplus killing” behavior, where cats hunt beyond their caloric needs, significantly amplifies their impact on local wildlife populations. Feral cats, which depend solely on hunting for survival, spend up to 12 hours daily actively pursuing prey. Free-roaming domestic cats, while often subsidized by owners, still hunt instinctively for several hours each day, contributing to the overall predation pressure. Domestic cats can reach much higher population densities than natural predators due to human care and feeding, further exacerbating their effect on native species.
Conservation and Mitigation Strategies
Addressing the impact of cats on wildlife requires a multifaceted approach involving both individual pet owners and broader conservation initiatives. For individual cat owners, the most effective measure to protect native wildlife is keeping cats indoors, which eliminates their access to potential prey and safeguards the cats from outdoor hazards. While measures like bell collars or brightly colored collars are sometimes used, their effectiveness in preventing predation is limited.
On a larger scale, conservation organizations implement programs to manage and remove feral cat populations, particularly from sensitive island ecosystems. These eradication efforts are especially successful on smaller islands, where reinvasion can be more easily prevented. Such initiatives are aimed at protecting endangered native species and restoring ecological balance.