In 1935, Australian government released 2,400 toads to destroy crop-eating beetles. Almost 100 years later, 200 million giant toads threaten 75 wildlife species

They were brought to Australia by the government from Hawaii to combat a pest that wrecked crops once upon a time. Fast forward 91 years, they have become nothing short of an unstoppable disaster in Australia, and there are 200 million of them! As per a BBC report, these toads are a triple threat – they are enormous, poisonous, and highly adaptable. Australia’s cane toad crisis can be traced back to Puerto Rico, where the giant amphibians were imported from South America to control grubs that were damaging sugar cane crops. Beetles were wreaking havoc on Australia’s sugar cane crops in Queensland.

The Unthinkable Happened

The beetle larvae lived underground, feeding on sugarcane roots and damaging the plants by slowing their growth or killing them entirely. So the government decided to bring an even larger predator to curtail their population.

According to the National Museum of Australia, in 1935, entomologist Reginald Mungomery, associated with the Bureau of Sugar Experiment Stations, travelled to Hawaii, where the toads had been introduced from Puerto Rico to combat beetle infestation. He captured a breeding sample and returned to Gordonvale near Cairns, where the toads successfully reproduced in captivity. That same year, in an attempt to control the pests naturally, the Australian government released 2,400 toads in the area, hoping the amphibians would devour the grubs and protect the sugarcane crops. However, to their immense disappointment, the toads had no impact on the beetle population. This was due to several factors – the cane fields did not prove to be sufficient shelter for the predators during the day, the beetles live on top of the sugarcane crops, and cane toads were not good climbers. They thrived in Australia’s warm, humid climate and lack of bigger predators that could eat them. This caused them to multiply and become a bigger threat than the government could have ever anticipated.


Cane toads spread gradually in the early years, but by 1959, they had established themselves across much of Queensland’s eastern coast. Their range expanded further, reaching the Gulf of Carpentaria in 1964, the New South Wales border by 1978, and the Queensland–Northern Territory border by 1984. By 2011, their population was estimated to exceed 200 million. The invasive species has also been linked to disease transmission and disruptions to native biodiversity.

How The Solution Became An Invasion

In 1950, the Australian government categorised cane toads as an invasive predatory species due to the ecological harm they might inflict. These amphibians endanger local wildlife by poisoning animals that eat them, competing with native species for food and living space, and heavily exploiting available resources.

The Queensland Government has claimed that no less than 75 species of Australian crocodiles, lizards, and freshwater turtles are endangered due to this invasive species. Wildlife at risk of deadly poisoning from consuming these amphibians also includes monitor lizards, quolls, tiger snakes, and freshwater crocodiles, many of which are already considered threatened. Cane toads possess a strong toxin called bufotoxin, which makes them hazardous at all stages of their life cycle, including both egg and tadpole phases. The compound is fatal to predators that consume it, while skin contact may cause only mild irritation to human eyes.

Researchers have recorded marked decreases in indigenous animal numbers after the introduction of cane toads. Northern quolls, Mertens' water monitors, and Mitchell's water monitors have faced major declines in invaded regions, leading to their endangered condition. The populations of goannas and snakes have also declined sharply in various areas. In certain regions, yellow-spotted monitor numbers fell by up to 90% following the arrival of cane toads in their environments.

A preliminary evaluation of the ecological dangers caused by cane toads in Kakadu National Park recognised native species consuming the poisonous amphibians as the gravest risk to biodiversity. Rivalry for food and other resources, as well as cane toad hunting and native animal hunting, were deemed relatively minor issues, though additional examination was suggested.

In the Northern Territory, several goannas (a type of lizard) have been reported dead after they devoured cane toads. These deaths have also been linked to the rising number of intact saltwater crocodile eggs.