In 1935, an Australian entomologist shipped 102 cane toads from Hawaii to fight crop beetles; 2,400 were released before anyone tested the plan

Nearly a century ago, a small group of Australian scientists brought about 100 toxic toads into their country to solve a farming problem. Nobody checked if the toads would even eat the right bugs. Today, there are millions of these toads across Australia, and they are extremely difficult to control.

According to the National Museum of Australia, this all started with a very real problem: beetles were destroying Australia's sugar cane farms. The fix scientists chose is now considered one of the biggest backfires in environmental history.

A beetle problem with a wild solution


Back in the early 1900s, sugar cane farming was booming in Queensland, Australia. But there was a catch. Native beetles kept eating the roots of the cane plants. Farmers were losing money every year, and nobody had a real fix.

According to the National Museum of Australia, government scientist Arthur Bell attended a conference in Puerto Rico in 1932 and learned that a large toad from Central and South America was being used there and in Hawaii to eat similar pests. Three years later, in June 1935, entomologist Reginald Mungomery flew to Hawaii to collect some of these toads. He caught 102 by hand and packed them into small boxes for the trip home. According to the Queensland Historical Atlas, a historical project run by the University of Queensland and Queensland Museum, one of the male toads died during the three-week boat journey, leaving 101 survivors.

By August 1935, according to the National Museum of Australia, the surviving toads had bred rapidly in captivity, and 2,400 of their offspring were released into the wild near Gordonvale. There was just one small issue. Nobody had actually tested whether the toads liked eating the beetles that were destroying the crops.

The plan that never got tested
Here is the part that still stands out today. The Australian cane beetles lived higher up on the plant, out of reach for a toad that mostly stays on the ground. The toads apparently never came into contact with the pests they were brought in to control.

Instead, the toads spread out and ate almost everything else: insects, small animals, and even each other's young. According to Florida's Fish and Wildlife Conservation Commission, cane toads carry a strong poison in parotoid glands on their backs, which is toxic enough to kill pets and other animals that try to eat them. So, when native predators like snakes and goannas tried to eat them, many died instantly.

Entomologist Walter Froggatt warned the government right away that the toad could become a serious pest, and he convinced health officials to ban further releases. In 1936, under pressure from Queensland's government and the media, Prime Minister Joseph Lyons reversed that ban. By 1950, the toad was officially declared a pest species.

They are now faster than nature intended
The study, ‘Invasion and the evolution of speed in toads,’ published in the journal Nature by biologist Benjamin Phillips and his team, found that cane toads at the edge of the spreading population have actually evolved longer legs over just a few decades. Longer legs mean faster movement, so the toads leading the invasion are literally built to travel further than the ones behind them. That is evolution occurring over time, driven by an accident nearly 90 years ago.

Today, the National Museum of Australia notes that cane toads move west across the continent at roughly 25 to 37 miles a year, and the Australian government has said there is unlikely to ever be a way to control them across the whole country.

America has cane toads too
According to the U.S. Geological Survey's Nonindigenous Aquatic Species database, cane toads are already established in Florida, Hawaii, Puerto Rico, and several other US territories. They were brought to Florida around the same era, also to protect sugar cane, and extra toads escaped or were released as pets in later decades.

If you live in central or south Florida, there is a good chance a cane toad has passed through your backyard. They are toxic to dogs and cats, and wildlife officials there still deal with fallout from a decision made generations ago, much like Australia does.

Scientists have not given up
Even now, researchers are trying to fix what 1935 could not undo. According to a 2025 report by ABC News, Australian scientists have gene-edited cane toad tadpoles, nicknamed "Peter Pan" tadpoles, so they never grow up and instead eat other cane toad tadpoles. It is an early experiment, not a nationwide fix, but it shows how seriously this problem is still taken 90 years later.

Why this story still matters
This whole episode is a reminder of something simple. Moving one species into a new place, even with good intentions, can change an entire ecosystem for generations. Scientists call this biological control, the use of one species to control another. When it goes right, it can save crops without chemicals. When it goes wrong, as it did here, it can take a century or more to undo, if it can be undone at all.

The cane toad was never the villain here. It was just doing what any animal does: surviving and reproducing. The real lesson is about testing an idea properly before letting it loose in the world, a lesson just as true for a lab experiment today as it was for a box of toads in 1935.