Invasive & Introduced Species
Tasmania’s isolation once offered protection from many mainland pressures, allowing unique plants and animals to evolve over millions of years. But over time, the island has become home to a growing number of non-native species that now pose a serious threat to its fragile ecological balance. This page explores the different ways invasive species affect the landscape, from forest to coastline.
Feral Cats
Silent Hunters in the Shadows
Feral cats are among the most destructive invasive species in Tasmania. Unlike domestic pets, these wild-living cats survive by hunting native animals, and their impact is devastating. One cat can kill multiple animals a night, targeting small mammals, birds, reptiles and insects with silent precision.
Many of Tasmania’s native species never evolved with feline predators and have no effective defences. For threatened animals like the eastern quoll, bettong, and ground-nesting birds, feral cats are a constant danger. Cats are also a primary host for the parasite Toxoplasma gondii, which causes toxoplasmosis in marsupials and can lead to population decline.
Managing feral cats is complex and controversial. It requires long-term strategies that balance conservation with ethical responsibility. Community awareness, responsible pet ownership, and science-led control programs all have a role to play in reducing their impact on Tasmania’s wildlife.
Explore → /responsible-cat-ownership
Other Introduced Predators
Unexpected Threats to Wildlife
Tasmania is facing growing pressure from a range of introduced species beyond feral cats. Feral deer now occupy more than a quarter of the state and are expanding rapidly. Their hard hooves damage soil, native vegetation and waterways, while their browsing habits reshape understorey habitat relied on by many native animals. Despite these impacts, they still retain partial legal protection in some regions, complicating efforts to reduce their numbers.
Another often-overlooked threat is the sugar glider, introduced from mainland Australia. While charismatic, sugar gliders prey on the eggs and chicks of hollow-nesting birds — especially the critically endangered swift parrot. Without natural predators or population controls in Tasmania, their presence has had devastating consequences in key nesting areas.
In the marine environment, the Northern Pacific seastar is an aggressive invader. Found in estuaries and coastal zones, it feeds on shellfish and competes with native species for space and resources. Its spread threatens delicate underwater ecosystems, including the remaining habitat of the red handfish, one of the world’s rarest marine animals.
Invasive Plants and Weeds
Shifting the Ground Beneath Us
Invasive plants may not stalk their prey, but they can be just as harmful to wildlife. Weeds like blackberry, gorse, pampas grass and Spanish heath outcompete native vegetation, disrupt habitat structure, and alter the way animals interact with their surroundings. Once established, they can be extremely difficult to remove.
Some invasive plants change fire patterns, increase erosion, or create monocultures that reduce food and shelter for native species. Others smother forest understorey or clog waterways, fragmenting the habitats that animals rely on to move, breed and find cover. Even familiar garden plants can become ecological hazards if left unmanaged.
Tasmania’s fight against invasive weeds involves government bodies, landowners, conservation groups and volunteers. Early identification, active removal, and replanting with native species are key tools in reclaiming wild spaces for the animals that depend on them.
Understanding Invasion Ecology
How Species Become Invaders
Invasion ecology is the study of how species move beyond their natural range and disrupt the balance of new ecosystems. In Tasmania, human settlement has accelerated this process, both intentionally and by accident. From escaped pets to stowaway seeds, the island has become home to a range of invaders with lasting impacts.
Invasive species often spread rapidly, taking advantage of ecosystems with no evolved resistance to them. They can alter food chains, compete with native species, introduce disease, and change the landscape itself. The effects are rarely isolated, one invader often leads to a cascade of consequences across multiple species.
Understanding how and why species become invasive is key to preventing future introductions and managing existing threats. This page explores the science, terminology, and challenges of invasion ecology, offering insight into one of the most pressing conservation issues of our time.