On the edge of a dark suburban park in Brisbane, teams of volunteer frog hunters gather around Gary King as he pushes another writhing specimen into a cooler box.
“Who has some more?” asks King, the local leader of this year’s Great Cane Toad Raid, a small and ultimately futile campaign to crush Australia’s massive invasive population of about 200 million.
The brown, warty-skinned pest, native to South and Central America, has been causing havoc in Australia since it was released to eat cane beetles in the northern state of Queensland in 1935.
They have since spread thousands of miles north, south and west, hitchhiking on vehicles and evolving stronger, longer legs to cross state lines, poisoning native fauna with their poisonous glands as they go.
Australia isn’t the only country with a cane toad problem; The United States, Japan, the Philippines, Papua New Guinea, and islands in the Pacific and Caribbean also host this species, either by accident or in false hopes that they will solve another pest-related problem.
Cane toads are frowned upon in Australia because the bulbous amphibian is a voracious eater and, when stressed, releases a toxin powerful enough to kill lizards, snakes, crocodiles – pretty much anything that dares attack it. In a suburban environment that includes dogs and cats.
Frogs are poisonous at all stages of their life cycle, and ingesting their poison, which is emitted from large glands on their shoulders, can cause rapid heartbeat, convulsions, paralysis, and even death in some animals. It can cause severe pain in humans.
For the most part, the fight against cane toads is waged by local ecological warriors wearing rubber gloves who comb the streets in search of adult toads. But the Australians have a secret weapon not yet available worldwide: a bait that attracts cane toad hatchlings and kills thousands in one hit.
Cane toad culling
King’s volunteer frog hunters in Brisbane include father-son team Luke and Austin Rogers, who moved to Australia from the UK more than a decade ago.
They don’t normally do this kind of thing; fishing is more typical of father-son trips.
But as you scan the ground wearing rubber gloves and a head torch, the competitive element of frog catching kicks in, providing the same dose of adrenaline as the first bite of the hook.
Luke spots a rather large specimen in a puddle, but when he bends down to grab it, the animal jumps and he follows, triumphantly slipping it into a bucket that grows heavier with each grab.
Does he think he’s dealt a big blow to the population?
“I do half of it because I enjoy it,” he says. “There’s definitely a part of me that thinks we won’t even scratch the surface.”
A more effective method to eradicate the frogs has already been invented, targeting tadpoles hatched in numbers of up to 30,000 eggs.
This is a collaboration between natural products chemist Professor Rob Capon of the University of Queensland and evolutionary biologist and ecologist Professor Rick Shine of Macquarie University.
Shine, one of Australia’s leading authorities on cane toads, had noticed that cane toad hatchlings could swim to eggs laid by rival females, even in murky water, and eat them to build up stores of nutrients and toxins.
In the laboratory, Capon set out to find out why.
“It turns out they were following some kind of chemical cue that the eggs were releasing,” Capon said.
To prove the theory and try to imitate it, they would first need a pile of dead cane toads.
Capon said initial efforts to obtain bodies were somewhat foiled by the university’s ethical obligations to ensure that animals were killed humanely for scientific study.
It was difficult to guarantee a humane death in a state where frogs were once hunted with hockey sticks and golf clubs in an unofficial sport.
“I grew up being told that killing cane toads was fun, and that you could do it in ways that caused as much pain to the animal as possible,” says Shine, who was born in Queensland.
“I guess my perspective right now is: It’s not the frog’s fault. “He did not come to Australia of his own free will,” he said.
“We want to get rid of them, but we have to do it in a humane manner, as if we were trying to get rid of koalas.”
The beginning of the fight
To satisfy the university’s ethics committee and obtain the required number of dead frogs, Capon and his team created the “Cane Frog Challenge.”
The program encouraged backyard hunters to find frogs and submit their catch. And the university collected enough dead frogs for several years of testing.
During this time, Capon and his team identified the pheromone that attracts tadpoles, extracted it from the frogs, and turned it into a liquid that could be used as bait.
The bait, a soaked stone, is placed in a trap sunk near the tadpoles, encouraging them to swim out of a hole.
The recommended method for killing tadpoles and adult cane toads in Australia is to put them in the fridge for 24 hours, then freeze them for another day or two before throwing them away.
For obvious reasons, killing tadpoles en masse is much more efficient than harvesting fully grown adults, Capon said.
But even he admits that eradicating Australia’s cane toads is an impossible task.
“Frog fishing is amazing. Capturing tadpoles is a really good adjunct to frog fishing because if you collect the adults and eliminate the tadpoles, you have a bigger buffer for the next generation,” he said.
“But Australia is a big place. And there are many places where frogs live happily, where there is no one to catch or catch the tadpole.
“So unless you’re going to put an army of retirees on a bus through North Queensland every week of every summer, we can’t get rid of the frogs.”
problem in florida
The southwestern United States state of Florida has a warm climate similar to Queensland; There are plenty of cane frogs and not enough retirees to catch them all.
As in Australia, cane toads were introduced to Florida in the 1930s to attack cane beetles, but local theory suggests that their numbers actually increased by accident in the 1950s.
“The narrative going on now is that there were initial attempts, none of them worked, but then somehow this giant crate full of 20 or so frogs was blown open at the Miami airport. “They became established because it was warm enough down there,” said Jacob LaFond, a laboratory coordinator and instructor at the University of Tampa.
So far they haven’t ventured beyond the peninsula – it’s too cold up north – and they appear to prefer human habitats to Florida’s natural environment.
This means cats and dogs are more vulnerable than Florida’s wildlife, which is used to living alongside other species of poisonous frogs.
“There is no evidence of much toxic poisoning of native wildlife in Florida,” said Steve Johnson, professor of Wildlife Ecology and Conservation at the University of Florida.
“In Florida, cane toads are primarily a socioeconomic problem. If you have a dog that attacks or eats a toad and dies, if you’re a dog lover, that’s a big blow to you, and then there’s the expense of taking the dog to the vet,” he said.
Experts say there is no major government campaign to eradicate cane toads because Florida has bigger problems with invasive pests.
“We have giant Burmese pythons destroying much of the ecosystem in South Florida. We have iguanas building tunnels that disrupt our highway infrastructure. So I definitely understand why frogs are taking a backseat,” LaFond said.
That doesn’t mean no one cares.
Nikki Tomsett, invasive species project manager at Watergum, an Australian nonprofit that is about to start producing Capon’s tadpole baits, says most of the emails she gets from outside Australia are from Hawaii and Florida.
The baits can’t yet be distributed outside Australia – the group is still working out licensing issues – but Tomsett suggests this isn’t a quick fix for the US. More stringent testing in the field is needed to ensure native frogs, including the southern toad, are not bycatch.
“Because we are unfamiliar with the southern toad and the ecology of Florida, we will need to do more trials and a lot of research and development,” Tomsett said.
Slowing the cane toad’s progress
As Florida’s numbers increased, small businesses offering frog hunting services began offering regular frog care for homes.
As Australia takes a more DIY approach to the suburbs, state officials are mounting a much stronger campaign to slow their rapid march westward.
The cane toad’s front line is currently located near the town of Derby in Western Australia, and is moving towards the coast at a rate of about 50 kilometers (31 miles) per year.
This means it is likely to reach the coastline within the next two years, and authorities are trying to slow its progress while preparing native animals for the inevitable onslaught.
In addition to manual frog catching and tadpole baiting, native animals are fed cane toad meat laced with poison or nausea-inducing chemicals to make them sick.
The idea is that they learn not to eat cane toads before the arrival of large, poisonous adult males.
“We put these baits out right before the front line comes, and then when the cane toads come, that animal isn’t going to go to the cane toad because it’s already tried the sausage and felt sick,” said Sara McAllister, invasive species project manager. From the Western Australian Department of Biodiversity, Conservation and Attractions.
“If we let nature take its course and let large and highly poisonous frogs come into the environment first, then you’ll see a lot of animals dying.”
The style of bait depends on the targeted animals; They are selected with the guidance of local Aboriginal rangers who have in-depth knowledge of the land and its inhabitants.
Northern quolls (small carnivorous marsupials) are getting cane toad sausage, goannas are being fed tiny live frogs, and freshwater crocodiles are being fed cane toad legs with a dose of lithium chloride.
In Brisbane, the clear winner of the evening’s frog hunt was 9-year-old Connor Holmes, who caught 25 frogs in just over an hour with his father, John.
“We have a system, right? I hold the bucket. And it catches,” John said.
“Because I’m faster,” Connor explains.
They say they will go hunting for cane toads more often, even if it is just for one problem.
“I don’t think your wife would appreciate the bucket of frogs in the freezer,” says John. “That’s the problem.”
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