Backstory: Busting cane toads Down Under

Graeme Sawyer hardly looks like the manager of a multi-media company as he sloshes through a flooded mangrove forest in khaki shirt and shorts on a recent dark evening. The outfit may be vintage Crocodile Hunter, but unlike the late Steve Irwin, Mr. Sawyer has murderous intentions toward the animals he's stalking.

Sawyer is a top general in the defense against a literal amphibious assault – the invasion of the cane toad. The poisonous, warty enemy is legion; the defenders are desperate, resorting to traps, sniffer dogs, and sometimes taking up cricket bats and even hemorrhoid cream to do in the enemy. On this particular evening the strategy is to take as many toads prisoner – for later disposal – as possible.

"We won't be able to wipe them out, but by killing as many as we can, we can minimize their impact," he says, wiping away the sweat and warm rain streaking down his face on this oppressively humid night. "If you just let them breed up, then there'll be absolute devastation."

Sawyer is a founder of FrogWatch, the conservation group that has led the fight in northern Australia against the toxic invaders introduced in Queensland in 1935 to eat a beetle that was damaging the state's sugar-cane plantations.

The experiment was a disastrous failure – the cane toads (native to South America) ignored the beetles but began chomping their way through plenty of other wildlife, from frogs and tadpoles to small lizards. Worse, the poison glands on their backs made them deadly to the crocodiles, mammals, snakes, and birds that tried to eat them.

The toads adapted superbly to the heat and humidity of tropical Queensland, and within decades began pushing south into New South Wales and west into the vastness of the Northern Territory. A couple of years ago they overran Kakadu National Park – made world famous by the Crocodile Dundee movies – and now they're on the doorstep of Darwin, capital of the Northern Territory.

While the task of capturing and killing toads on the ground is left to unpaid volunteers, the federal government in Canberra spends a modest $740,000 a year on cane toad control research, largely through its scientific agency, the Commonwealth Scientific and Industrial Research Organisation. CSIRO scientists are trying to find pathogens and other deadly infectious agents that could be used to wipe out the pests.

Sawyer leads a grass-roots campaign that is trying to prevent toad numbers from building to the point that they'll wreak havoc on the city's wildlife and domestic pets (a mouthful of toad can be fatal to a dog or cat).

Sawyer had a broad interest in the environment when FrogWatch was founded in 1991, he says. "We were looking at frog populations and distributions. We found a new species – a whole bunch of stuff like that."

But gradually he turned his attention to the impending threat posed by the toads as they hopped and croaked their way in their millions across Australia's tropical north. "The closer they got to Darwin the more political and community concern there was," he says.

He started organizing toad "musters" – a word reflecting Northern Territory's status as cattle country. But instead of the motorbikes and helicopters used to herd bovines, toads have to be rounded up the hard way – one by one, by as many volunteers as can be persuaded to give up their evenings to stem the amphibian invasion.

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On tonight's muster, about 30 locals – adults and children – have gathered at the Casuarina Coastal Reserve, a strip of bushland on Darwin's fringe, armed with powerful flashlights and clear plastic sacks.

Sawyer issues directions like a commander deploying his troops. "We'll sweep through the nature reserve in both directions," he tells them. "You should be able to see them from the reflections of their eyes. Just walk up to them, grab 'em from behind and put them in the bag. Simple."

The volunteers fan out into the darkness, nonchalantly stepping around a poisonous brown tree snake as it slithers through the wet grass.

"I caught three [toads] on my first outing. I find them repulsive," says Marilyn Bartels, an accountant, the beam of her flashlight slicing through the darkness.

Within a few minutes, two toads are found lurking in the undergrowth. They're unceremoniously scooped up and dropped in a sack. A large cane toad – Latin name Bufo marinus – resembles a half-deflated football and can fill the bottom of a bucket, weighing in at a hefty 1.3 pounds.

"I grew up in Brisbane, and we used to see heaps of green tree frogs, but since the cane toads arrived you don't see any," says volunteer Stacey Anderson, an entomologist. "This is people power in action – we can stop them if we want to."

Sawyer emerges from the darkness clutching a dozen writhing toads in each hand. They will be rendered unconscious with carbon-dioxide gas and put in a big freezer. Toad carcasses are processed into liquid fertilizer distributed to nurseries and hardware stores around Darwin, where it sells for almost $10 a bottle. Preliminary results have shown it is especially good for growing bananas and papayas.

In addition to weekly toad musters, locals round up toads in their gardens and dispatch them with what's at hand (often golf clubs and cricket bats). The more squeamish can place their captured toads in FrogWatch's roadside "detention centers" in and around Darwin. These boxes are equipped with food and water to keep the toads alive until they can be humanely destroyed.

Australia's Royal Society for the Prevention of Cruelty to Animals advocates a more elaborate approach, advising people to smear hemorrhoid cream on the toads' backs, which makes them unconscious. They are then frozen in a freezer.

While Darwin is already besieged, millions of other toads are converging on Western Australia, hundreds of miles away. Efforts to head them off are difficult: The toads have a rampant libido and a female can lay up to 35,000 eggs at a time. Even the tadpoles are poisonous to native animals.

"They breed in extraordinary numbers," says Lee Scott-Virtue, an archeologist who leads the Kimberley Toadbusters, based in the remote town of Kununurra. "You go to a billabong and the whole bank will be moving with a carpet of toads."

The Toadbusters, she says, have "been at it for 19 months without a break. Over the weekend just gone we reached the 100,000 mark – that's adult toads and tadpoles, caught and killed."

The toad busters of Western Australia and the Northern Territory acknowledge that the best they can do is stem the onslaught while waiting for scientists to come up with a silver bullet capable of drastically reducing numbers.

Despite the enormity of the challenge, volunteers like Ms. Scott-Virtue remain fiercely committed to the cause. A year ago she was married in a toad-muster wedding – a simple ceremony in the bush, a toast to the couple, and then the whole party went off in the night in search of their quarry.

"We have a saying – if everyone in Australia became a toad buster, the toads would eventually be busted," she says.

Sawyer feels no hatred for the invaders. "I have a huge amount of admiration for them as animals," he says, dumping another fistful of toads into a sack. "I just wish they weren't in Australia."