Australian Bush:The Invasion of the Giant Cane Toads

It could be science fiction.It has already been featured on games videos. But in the Australian Bush there’s an extraordinary real problem which is entirely self inflicted.

In the 1930s some bright person thought they had found an ecological way of dealing with a pest – a beetle – that was destroying Australia’s sugar cane crop. They decided to import the world’s large toad that had been introduced to Hawaii from Central America. The toads grow up to six inches long.

What the people who imported the toad did not know is that this large toad could not jump. And the beetles lived at the top of the sugar cane some 15 feet above the ground. So the toads were less than useless in combating the pest.

But their legacy has been a disaster. The toads secrete a poisonous fluid when attacked as their main defence mechanism. Toads are the natural food for many native reptiles and birds. They have no natural predators in Australia.

Worse the reptiles and birds that ate them were poisoned threatening the diversity of wildlife and forcing snakes and iguanas to the point of extinction in some areas. They also multiplied from a few hundred to an amazing 200 million and expanding their area from a small part of Queensland into the vast Northern Territories.

One area we visited was Litchfield National Park south of Darwin. This bush park is famous for its waterfalls and its giant termite mounds. Here the arrival of the cane toad has seen the disappearance of iguanas and some species of snake who ate the toads.

The guide who took us on the trip was devastated by the impact of the toads on other wildlife. And he was concerned about the spread of the toads which extend their range by about 25 miles every year.

Obviously it has not destroyed all wildlife in the park. Some specialised species like the olive python which feeds on bats are largely unaffected. And there is some hope that Australian wildlife hit by the toads may be able to adapt.

One snake has evolved to have a smaller jaw so it cannot swallow a giant toad. A bird under threat has found that if you turn the toad belly up it is possible to eat parts of it without being poisoned.

And the park’s meat eating ants have found they are immune from the poison. Normally they invade the huge termite mounds and kill the termites. Now they have found toads as another part of their diet.

The Australian cane toad has also adapted. It has grown longer legs so it can cover greater distances in this huge continent. Meanwhile scientists have unraveled the toad’s DNA in the hope of finding a way to try and eliminate them. This is an extraordinary story of a self inflicted problem that could be solved by evolution.

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