Feral cats are a widespread invasive predator in Australia, representing a major threat to the nation’s unique native wildlife. A feral cat is defined as an unowned, unsocialized animal that lives and reproduces in the wild, surviving entirely without reliance on humans for food or shelter. Cats first arrived with the European First Fleet in 1788 and rapidly colonized almost the entire continent within 70 years. Their predatory nature has made them a primary driver of native mammal extinctions.
Current Population Estimates and Distribution
Estimating the total number of feral cats across a continent is complex, leading to figures that depend heavily on environmental conditions. The population in natural environments fluctuates between 1.4 million during extended dry periods and up to 5.6 million following heavy rainfall. This variability is linked to the boom-and-bust cycles of prey populations, such as native rodents and rabbits, which surge after rainfall events, allowing the cat population to multiply rapidly.
An additional 0.7 million feral cats are estimated to reside in modified environments, including urban fringes and farming areas. Factoring in these populations, the total number of feral cats in Australia ranges from a low of approximately 2.1 million to a high of 6.3 million. Feral cats are established across more than 99% of Australia’s land area, with the highest densities occurring in arid and semi-arid zones after wet seasons due to the temporary abundance of prey.
Ecological Damage and Predation Impact
Feral cats have been a contributing factor to the extinction of at least 20 native Australian mammal species since European settlement. They currently pose a threat to over 124 nationally threatened species, including small mammals, reptiles, and ground-dwelling birds. Estimates suggest that feral cats kill over 1.5 billion native animals annually, including mammals, birds, reptiles, and frogs.
Feral cats are effective hunters, with each cat killing an average of 791 native animals per year. They are successful predators because many Australian native animals did not evolve alongside placental carnivores, making them uniquely vulnerable to cat hunting techniques. Species within the “critical weight range” (35 grams to 5.5 kilograms) are the most susceptible to predation, including iconic marsupials like the bilby, numbat, and quoll.
Challenges in Counting and Monitoring
Accurately counting feral cats across Australia’s vast and remote environments presents significant scientific challenges. Feral cats are mostly nocturnal and elusive, making direct observation impractical for continental-scale population assessment. Researchers must rely on a combination of indirect methods and mathematical modeling to extrapolate estimates from localized density studies.
Researchers use several field methods to monitor populations:
- Motion-sensing cameras record activity and density for population modeling.
- Analyzing scat samples determines diet and genetic makeup.
- Track counts are conducted in prepared sand plots.
- Environmental DNA (eDNA) collected from soil or water confirms species presence without requiring a physical sighting.
National Strategies for Feral Cat Management
Predation by feral cats is formally listed as a “Key Threatening Process” under national environmental legislation. The current national strategy, detailed in the Threatened Species Action Plan 2022–2032, focuses on outcome-based targets to protect vulnerable species. Specific goals include implementing feral cat management across 100% of the important habitat for susceptible priority species by 2026.
Control efforts employ a mixture of landscape-scale and targeted tools. Aerial baiting is one of the most effective broad-scale techniques, utilizing specialized baits like Eradicat, which contains the toxin 1080 (sodium fluoroacetate). This bait is effective because native Australian species have a natural tolerance to 1080, a compound found in some native plants, while introduced pests do not. Targeted control also includes exclusion fencing to create large, predator-free havens on the mainland, and the complete eradication of cats from islands, such as the successful project on Dirk Hartog Island.