We think we have problems here with the grey squirrel, the aggressive American species introduced to Longford in 1911 and now rapidly chasing the native red into exile. But spare a thought for those Australians whose job it is to stop the spread of something called Bufo marinus. Because, as invasive species go, this one makes the grey squirrel look shy and retiring.
The cane toad, to use its better known name, was famously introduced to northern Queensland in 1935 as an attempt to control the sugar-cane beetle. Just as famously, it became a bigger pest than the thing it was brought in to attack. Soon it was clear that the species was going places - north and west of Queensland, namely - and its advance has continued to this day.
Chief among the toad's survival skills was the fact that it was highly poisonous. Bigger predators might eat it, but it was often their last meal. Bufo Marinus was also highly talented at breeding. And this, combined with an ability to adapt quickly to its surroundings, made the cane toad a runaway success in the competitive world of Australian wildlife.
Not for the first time this week, the unloved amphibian was provoking headlines down under that sounded like a plot summary from a 1950s B-movie. "Cane Toads Could Take Over Australia," yelled one. "Cane Toad the Size of a 'Small Dog' Found," screamed another.
The first - on the Australian Broadcasting Corporation's website - described new findings by scientists suggesting that the toad, which was previously thought to be extremely adaptable, is even more adaptable than that. Far from being confined to the hot, humid climes of northern Australia, as once assumed, the species has been found to cope with a wide range of temperatures and air moisture levels. It could therefore now be expected to colonise three-quarters of the populated areas of Australia, scientists said, adding that even this forecast "may prove conservative".
The second headline (from Tuesday's edition of The Australian) concerned a particular example of the species found in the Northern Territory, and dubbed "Toadzilla" in more excitable sections of the media. On closer reading it emerges that the "size of a dog" claim was tenuous. Another commentator said that, at a stretch, the specimen was the size of "a small chihuahua". Which is, of course, still impressively big for a frog.
Besides, as was pointed out by a member of the toad-monitoring group that found this specimen, there is almost certainly a bigger one at large. Graeme Sawyer of FrogWatch North explained that Toadzilla was a male and that male cane toads were in general smaller than females. "I would hate to meet his big sister," he quipped.
Not only do the invaders appear to be getting larger, they are travelling faster. Studies in Queensland in the 1940s suggested the "toad front" was moving at 10 to 20 kilometres a year. Recent estimates put it at up to 70 km - a rate of improvement that compares well with the car industry. This is partly an example of evolution at work, since longer-legged toads are more successful at surviving. But it may also reflect short-term tactical improvements in the species's behaviour. A 2005 study found that toads were travelling by road through Northern Australia, finding this quicker and easier than the bush. The research was carried out at a place called Fogg Damm, near Darwin, where the amphibians were tracked with GPS equipment.
"A toad will be hurtling down the Arnhem highway and then take a strong right turn on the road to Fogg Damm," commented Prof Rick Shine of the University of Sydney, whose team carried out the study. Toads radio-tagged by the researchers were found to be covering up to 1.8 km a night.
As a prime example of evolution, it seemed like a sick joke that for several years past, the cane toad was reported to be "advancing on Darwin". Residents of that city (Darwinians, presumably) dreaded its arrival and the mass poisonings of domestic pets - not to mention the risk to children - that would result. But so far, teams of "toad-busters" appear to have held the advance on the outskirts of Darwin, where Toadzilla was found, and the doomsday scenario has yet to materialise.
The cane toad is not quite indestructible. Those caught by the toad-busters are killed and turned into "foul-smelling but nutritious fertiliser". Meanwhile, some animal predators have devised ways to enjoy a fresh cane toad meal safely. Crows flip them onto their poisonous backs and eat them from the non-poisonous front, while crocodiles first give them a good dousing in water - a bit like preparing lettuce - to wash the toxins off.
Other carnivores, such as the northern quoll, have been less successful. A rabbit-sized marsupial that eats anything it captures, the quoll is described by one expert as "a species highly adapted for extinction". One of its problems, according to the science journal Nature, is over-vigorous sexual activity: "The males all die each breeding season, exhausted by frenetic mating." The quoll was no match for the cane toad, which is blamed for wiping it out in some areas.
As scientists continue to probe Bufo marinus for a weak link, its own sexual habits offer grounds for hope. In contrast to their general flexibility, cane toads have very particular preferences for where they like to breed: namely in shallow water, with a "gently sloping edge", surrounded by open ground. One possibility is that the toads' invasion could be slowed down by changing the shape of roadside culverts to make them less attractive. But nobody is overly confident.