Australia's most successful reptile invader ... the Asian house gecko. Photo: Bruce Cowell
THEY arrived by sea, probably stowed in the hold of a cargo ship, and like any invader advanced their territory through a combination of stealth and stamina.
Since the Asian house gecko arrived in Brisbane in the early 1980s, the cold-blooded creatures have spread to nooks and crannies in houses throughout the city and along the coastline of Queensland and northern NSW.
Their spread has been so rapid and far-reaching they hold the impressive title of the country's most successful reptile invader.
''They can hitch a ride anywhere with freight, they are prolific breeders and the [females] are capable of storing sperm so a single female is capable of founding a new population,'' said Patrick Couper, a herpetologist and curator of reptiles at the Queensland Museum.
In 2010, the Queensland Museum tried to map the distribution of geckos, which like warm and humid conditions and feed on insects.
Sightings were common along the entire Queensland coastline and northern NSW, and more than half the 4000 people surveyed reported geckos in their house since 2005.
They are now common along the east coast north of Coffs Harbour, but Mr Couper believes the reptiles could also establish themselves as far south as Sydney, where it could survive on the warmth of household hot water systems.
''The urban landscape suits them. You'll spot them around lights,'' he said.
The success of the Asian house gecko, like most invasive species, has come at a cost to its native cousins, which are being beaten to food and habitat by the foreigners. Geckos have also transferred disease-carrying mites to the native species.
Mr Couper estimates there are tens, if not hundreds, of millions of geckos in the country, which would make them impossible to eradicate with chemical control.
A biological control would be a threat to native lizards, he said.
A study by the museum's reptile collection manager, Andrew Amey, found Asian house geckos had even adapted their breeding cycles to suit Australia's climate.
In their native Asian habitats, where the temperature remained warm year round, females laid eggs once every month to five weeks, Dr Amey said.
But in Australia, the reptiles had begun shutting down their reproductive system during winter, he said.