Australia is one of the few large landmasses without a native population of squirrels, which belong to the family Sciuridae. The continent’s unique evolutionary history and long isolation allowed marsupials and other placental mammals to fill the ecological niches occupied by squirrels elsewhere. While squirrels are common sights in the parks and forests of North America, Europe, and Asia, their absence in Australia is maintained by the continent’s distinctive native fauna and a comprehensive system of government regulation.
Australia’s Strict Biosecurity Laws
Australia maintains a strong defense against the introduction of non-native species, a policy codified under the Biosecurity Act 2015. This national legislation classifies all squirrel species (Sciuridae) as prohibited pests, meaning their importation, keeping, or release is strictly forbidden without specific authorization. The nation’s island geography provides a natural advantage, allowing for aggressive quarantine measures aimed at preventing the entry of exotic diseases and animals that could devastate agricultural industries and native wildlife.
The Biosecurity Act replaced the older Quarantine Act 1908, strengthening the framework for managing risks associated with diseases and pests that could harm human, animal, or plant health. Squirrels are considered a significant threat due to their potential to compete with native species for food and nesting hollows, as well as their capacity to transmit foreign diseases. Specifically, the Northern Palm Squirrel (Funambulus pennantii) is listed as an extreme threat species nationally, given its destructive potential to fruit orchards and crops.
Any illegal importation of a squirrel, whether as a stowaway in cargo or through the illegal pet trade, is treated as a major biosecurity breach. The regulatory environment operates on a zero-tolerance principle for the establishment of pest populations. This proactive, legislative approach is a primary reason why squirrels have failed to establish widespread, self-sustaining populations, unlike other introduced pests such as rabbits or cane toads.
Documented Incursions and Eradication Efforts
Despite the rigorous laws, a few historical attempts to introduce squirrels resulted in small, localized populations that required immediate government intervention. The most prominent example involves the Eastern Grey Squirrel (Sciurus carolinensis), a species native to North America. These squirrels were released in the early 20th century in urban centers such as Melbourne, Ballarat, and Adelaide.
In Adelaide, a population of Eastern Grey Squirrels established itself around 1917, restricted largely to urban plantings of northern hemisphere trees. The South Australian government responded promptly and aggressively, controlling the population using a combination of active trapping by council staff and a public bounty system. This coordinated effort successfully eradicated the entire Adelaide population by 1922, preventing the species from spreading into natural environments.
Another species, the Northern Palm Squirrel, was introduced to the grounds of the Perth Zoo in Western Australia in 1898. This population expanded into surrounding suburbs, existing for over a century until a concerted eradication program was implemented by the Department of Agriculture and Food. The palm squirrel, an omnivore known for damaging fruit crops and preying on bird eggs, was eventually eliminated from the region, with the last known sighting confirmed in the 21st century.
Native Australian Animals Mistaken for Squirrels
Visitors who believe they have spotted a squirrel in Australia have likely encountered one of the continent’s native marsupials or rodents. The Common Brushtail Possum is frequently mistaken for a large squirrel due to its thick, bushy tail and arboreal habits. Possums are marsupials, distinguished by the female’s pouch for carrying young, a feature entirely absent in placental mammals like squirrels.
Smaller, more agile creatures also confuse observers, particularly the Sugar Glider, a small marsupial that resembles a flying squirrel. The Sugar Glider possesses a gliding membrane, called a patagium, which stretches from its wrist to its ankle, allowing it to glide between trees. Native Australian rodents like the Black-footed Tree-rat occupy a similar ecological niche to squirrels. This arboreal native rodent forages for seeds, fruits, and flowers, but it lacks the characteristic morphology of the squirrel family.