Canada and the World
Current Events with a Canadian Perspective
Last update
19 November 2010
Controlling Invasive Species
People in Australia and in England are trying
to get rid of invasive species, just as the
Chinese attempted to do fifty years ago
In 1935, sugar cane growers in Queensland, Australia imported 102 cane toads (below) from Hawaii. The toads were given 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 in April 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 high up in 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-
Toad Day Out
The cane toads have become among the most disliked critters in Australia. As the Brisbane Times reported in March 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 Sydney Morning 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 to meet their maker in science classes at schools and universities. A few of the larger specimens will be stuffed and mounted. 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, 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 (left) 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 in April 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-
As part of the assault on sparrows, the population was mobilized to tear down nests and eggs and nestlings destroyed. 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.
Image credits
Bidgee
Nick Fraser
Ray Eye
Schick
Sources
“Overstaying their Welcome.” Tina Butler, Mongabay.com, April 17, 2005.
“Thousands Killed in Toad Day Out.” Jamie Duncan, Brisbane Times, March 30, 2009.
“Introduction of the American Grey Squirrel in Europe.” Bertolino Sandro, Current Science, October 10, 2008.
“Grey Squirrels Culled for Red.” BBC News, April 15, 2008.
© Canada and the World, September 2010
All rights reserved
European red squirrels were once abundant all over the British Isles. Today, says the Forestry Commission there are only about 140,000 left, of which 85% are in Scotland, while there are 2.5 million grey squirrels.
“Critics of the toads blame them for the deaths of crocodiles that may have feasted on them, inadvertently poisoning themselves.”
A NEW TACTIC
According to CBC News (February 19, 2010) “Researchers with the University of Sydney
found that a few tablespoons of cat food left next to ponds in the Northern Territory
attracts fierce Australian meat ants, which then attack baby cane toads as they emerge
from the water.