Organized Pest Control
In 1935, sugar cane growers in Queensland, Australia imported 102 cane toads from Hawaii. The toads were to have the job of eating cane beetles that were destroying the crop. Within six months, the toads had multiplied to around 3,000 and they were set loose in the cane fields.
As Tina Butler at mongabay.com reported on April 17, 2005, “The plan backfired completely and absolutely.” The toads aren’t very good at the high jump and the beetles they were supposed to snack on lived near the tops of the cane plants.
So, the toads turned to other things for their lunch – insects, bird’s eggs, and native frogs. Worse still wrote Tina Butler, “…because the toads are poisonous, they began to kill would-be predators. The toll on native species has been immense.”
Toad Day Out
The cane toads have become among the most disliked critters in Australia. As The Sydney Morning Herald reported on March 29, 2009, “Millions of them now threaten many local species and spread diseases such as salmonella across northern Australia.”
Queensland Member of Parliament Shane Knuth came up with a solution to the problem. He organized a festival aimed at eliminating some of the toads. This “was staged,” wrote Jamie Duncan in The Herald, “to raise awareness of humane ways of catching and disposing of the toads. Prizes were awarded to children for the heaviest individual toad and heaviest total weight of toads.” The biggest toad weighed in at just over half a kilo.
Most of the amphibians will go meet their maker in science classes at schools and universities. However, at best, the northern Queensland cane toad population has been reduced by a few thousand. As each female can lay up to 10,000 eggs a year, the problem is far from solved.
The American Grey Squirrel
Across the world, there’s another scheme to get rid of an imported pest. The Essex Wildlife Trust wrote about the American grey squirrel in its May 1997 newsletter. It said the first grey squirrels were deliberately imported and released in Britain in the 1820s. The Trust gives an explanation for what turned out to be misguided actions: “The most likely answer is that acclimatization of species, as they called it, fitted in with the Victorians’ view that man’s task was to reshape the world in all its aspects and it became the fashionable thing to do.”
It didn’t work out well for the native red squirrels. Bertolino Sandro in a paper published in Current Science in October 2008 points out that, “Grey squirrels compete with the native species mainly for food; furthermore, they can maintain and spread a poxvirus, which causes a lethal disease in red squirrels in Britain.” Bigger and more aggressive, the grey squirrels have pushed the reds out of many habitats and threaten them with extinction. So, as BBC News reported on April 15, 2008 attempts are now being made to exterminate grey squirrels from areas where the red squirrels still have a chance for survival.
Mao Zedong’s Four Pest Campaign
China’s long-time leader Mao Zedong launched his Great Leap Forward in 1958. Part of this ambitious plan was the Four Pest Campaign; an attempt to eradicate the country of rats, flies, mosquitoes, and sparrows.
As part of the assault on sparrows, the population was mobilized to tear down nests and destroy eggs and nestlings. Citizens were ordered to bang pots whenever sparrows landed to frighten them into the air causing them eventually to plummet to the ground, dead from exhaustion.
This also did not turn out well as recorded in “Mao Zedong” by Jonathan Clements in his 2006 book. “There were no sparrows the following year to steal grains of wheat but there were also no sparrows to prey upon the population of caterpillars, resulting a plague of the insects on China’s grain crop.”
Meddling with any single aspect of the environment can lead to unintended consequences.
