Every night under cover of darkness an advancing wall of toads heads west. Rather than winding through the bush, the toads march straight down the highway, ignoring the official border signs.
Meanwhile, on the Western Australian side of the border, perch gangs of volunteers from the Kimberley Toad Busters awaiting the toad arrivals. The border gangs capture the creatures in plastic bags, gas them, then measure, weigh and tag them before dumping them into mass graves.
Futile efforts in the face of the so-called “unending hordes”, “the invasion front”, “public enemy number one”, or just plain old “vermin”?
Rewind 23 years to 1988 to a scene you may remember. A Queensland Kombi driver weaves purposefully all over the road, his van leaving squashed animals in its wake. “Pop” goes each toad as tyre strikes flesh, while he describes utter revulsion for this amphibian and his love of native wildlife.
Both these scenes, captured in Mark Lewis’s first and second cane toad films, Cane Toads: An Unnatural History (1988) and Cane Toads: The Conquest (opens June 2), are poignant images of human futility in the face of rapid animal evolution.
The brazen success of bufo marinus in the Australian environment – the way it has assimilated, hybridized and utterly thrived - undermines the notion of human supremacy over nature.
While our capacity for progress seems limitless, says one scientist in The Conquest, we still haven’t found a way to combat the toad. Despite vocal protests from locals upon their arrival in a new area, and events like the annual “toad day out”, the reptile is now firmly entrenched in many parts of the country as well as in the Australian human (and probably animal) psyche.
The problem began in 1935 when 102 toads were imported from Hawaii to save Queensland cane crops from devastation by the greyback beetle. Given the differing life-cycles of the grub and the toad, and the fact that toads can’t fly – yet – their introduction is considered by most scientists to be an environmental blunder of monumental proportions.
Some estimates put their population at around 1.5 billion. According to Adrian Franklin, author of Animal Nation: the true story of animals in Australia, the toad was introduced at a time when economic value was upmost and wildlife impact an afterthought.
But the blunder demonstrates the dangers of too simplistic a view of animal ecology as being fixed as opposed to being adaptive and dynamic.
Thankfully the dire prediction made in the first film by a young Dr Mike Archer — now Professor and (former) Dean of Science at UNSW — that most of the big carnivores would be wiped out creating a monoculture, hasn’t materialized. In a scene worthy of an Oscar, an anguished and effusive Archer describes the tortured death his adored pet quoll endures after feasting on bufo marinus.
Remarkably within the space of 70 years some species of animals that were close to extinction 30 years ago because of the cane toad have adapted to their poison and even replenished their numbers.
As far as Professor Rick Shine (one of the foremost researchers on the toad based at Sydney University’s Institute for Sustainable Solutions) knows, no species have become extinct as a result of the introduction of the cane toads to Australia. But how the native animals evolve to accommodate the toad continues to baffle evolutionary ecologists.
Bufo marinus’s exceptional evolution and behavior also fascinates Australian scientists. Originally they believed the toads wouldn’t be able to migrate across the vast northern river systems nor endure the region’s long dry. Yet the toads have rapidly mutated into remarkable dispersal machines, claims Shine.
Having evolved the longest back legs, the swiftest then reproduce on the “frontline”.
Exploiting the paths of least resistance – multiple corridors of Northern Territory roads – enables the athletic toad to penetrate further and faster into the NT and WA. Shine calls this the “Olympic village effect”.
Even Shine’s research career reveals adaptations because of the toad. He began as a reptile expert, focusing on the evolution of crocodiles in the NT. The he noticed his research subjects dying in vast numbers so he started studying the maligned villain killing his crocodiles.
At a recent community screening of the 1988 film at Petersham Bowling Club in Sydney, one audience member asked Shine why Australia boasts all the foremost bufo marinus experts. Shine’s laconic response: “Because no other country really cares about them”.
Cane toads have attracted significant Australian research interest and millions of dollars in grants over the years. The CSIRO once had an $11m grant to genetically engineer a virus to restrict their numbers.
This was abandoned when it was realized that with strong winds this virus would drift over mainland Indonesia, home to many vulnerable native toad populations. Native toads of Indonesia are vital to their own ecosystems, controlling insects like malaria-born mosquitoes.
While Shine agrees that there is a place for intervention into nature when it comes to toads, he thinks that this should be done humanely and as “naturally” as possible.
The Conquest is a more sophisticated film than its predecessor and often conjures a sense of empathy for the toad. But the satirical and absurdist humour that made the first film a “cult classic”, is still palpable.
During question time at the Sydney Film Festival screening last year Mark Lewis played down the film’s technological achievements - as Australia’s first 3D film - and seemed prouder that The Conquest featured the world’s first dog hallucination scene. Dobbie, a canine crossbreed, has become addicted to licking toads for their hallucinatory high. Even the film’s poster carries a warning: “licking this toad can be hazardous to your health”.
Cornell historian Dominick La Capra has claimed that the 21st century will be the century of the animal. Cane toads have provoked scientists to re-think their understanding of animals’ evolutionary and adaptive capacities. Mark Lewis’s film is a humorous but at times melancholic plea to re-think our relationship with the much-maligned toad.