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Spiders keep cane toad numbers in check

Toxic cane toads may have met their match in native Australian spiders like the wolf spider and Australian tarantula.

FROM CROCODILES TO SNAKES and quolls, many Australian species have died trying to eat the indestructible cane toad. But it seems that some native spiders have found a way to consume large numbers of the large toxic pest.

Spider expert Dr Robert Raven, from the Queensland museum, says three families of spider - Australian tarantulas, wolf spiders and racing stripe spiders - may be helping to keep northern Queensland cane toad numbers in check.

"That spiders eat cane toads is not uncommon or unknown," says Robert. "The interesting thing is size of the toads they are able to take. In one instance, the toad was bigger than the opening of the spider's burrow."

Natives fight back: spiders vs. cane toads

Although the Australian tarantula (Theraphosidae sp.) is able to kill and eat larger toads, says Robert, the more common wolf spider (Lycosidae sp.) may be a better candidate for reducing the number of cane toads.

"Tarantulas and wolf spiders both kill dogs and cats quickly, in around thirty minutes to an hour with one bite," says Robert. "However, tarantulas are quite low in number, and they're becoming rarer because of humans."

Introduced into northern Queensland in 1935, the cane toad releases a fatal toxin to vertebrates, causing rapid heartbeat, excessive salivation, convulsions and paralysis.

Robert believes that although the dangers to vertebrates are known, research needs to be done on the effects of the toxin on invertebrates, which at this time are unknown.

"With cane toads, the toxins have to be ingested for them to be effective," says Robert. "However, the spider, in order to eat, vomits a proteolytic enzyme into the animal, which may cause the toad venom to [become inactive]."

Native animals picky cane toad eaters

Although cane toads are devastating for a small number of large predator species - including goannas, blue tongue skinks and quolls - their impact doesn't appear to be permanent, says toad expert Professor Rick Shine, from the University of Sydney.

"Even these species eventually seem to recover a few decades after the toad's first arrival, so the long-term impact of cane toads probably isn't as great as that of animals like rabbits or cats," says Rick.

Other native Australian invertebrates are able to eat cane toads, including meat ants and water beetles, which consume millions of toads every year, according to Rick.

Other natives that prey on cane toads include the Australian crow (Corvus orru), which has adapted by eating them from the underbelly to avoid the venom, and the saw-shelled turtle (Wollumbinia latisternum), adds Robert.

Ants keep toad tadpoles in check

Studies both in the lab and around breeding ponds in the field have revealed that ants, in particular, can significantly reduce the number of young cane toads.

"What we don't yet know is how a reduction in the numbers of small toads ends up influencing the number of adult toads in an area," says Rick. "But, we are hoping to conduct research on that question also."

When it comes to conservation, Rick believes that increases in predator numbers may help explain why toad numbers drop after they have been in one area for a long time. "Basically, the native predators recognise that there is a new free food source and start to exploit it."

However, despite being hopeful that a combination of methods will see a drastic reduction in cane toad numbers, Rick warns that "eradicating toads from Australia simply isn't possible."

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CANE TOADS - WHAT A PEST!

The cane toad was introduced into Gordonvale, Queensland (22km south of Cairns) in 1935 from Hawaii to combat the sugar cane beetle which was destroying the crops of the sugar cane industry. It has since hopped all over Queensland and is now entering neighbouring states.

The Toad is presently considered a major pest and a threat to native wildlife. All efforsts are now being made for its eradication. The skin of the Cane Toad is strong, tough and durable and maes up into excellent leather goods.

Chinese medicine manufacturers have been using the Toads for centuries in the treatment of cardiovascular diseases and cancer. It is highly likely that the Cane Toad will one day be farmed in Queensland in high volume for production of therapeutic medicines for mankind. A reversal - from pest to life saver.

Some Facts Abut Cane Toads   (courtesy of www.canetoadstheconquest.com)

· 102 cane toads were introduced to Australia in 1935. There are now more than 1.5 billion of them.

· The toads now occupy over 1 million square kilometres (620 000 square miles) of territory.

· In 2010, the cane toads have advanced as far west as Kununurra, just inside the Western Australian border. This is a distance of about 2,424 km or 1,506 miles.

· Cane toads have an especially strong drive to mate and have been observed in their over enthusiasm mating with rocks, clumps of dirt, human feet and roadkill.

· Cane toads mostly eat insects, but they will eat anything that fits into their mouths – living or dead. Analysis of a cane toad’s stomach contents has revealed various insects, rocks, sticks, small mammals and other cane toads.


· In 2007 ‘Toadzilla’ was captured in the Northern Territory. He was 20.5cm long and weighed 840 grams (1.9 pounds).


· In 1988, Dr Glenn Ingram, a Queensland Museum zoologist, was given an enormous cane toad called Big Bette. Big Bette measured 22cm (8.6 inches) in length and weighed 1.8 kilos (4 pounds) - about the same weight as a Chihuahua.


· In 1975, a submission was made to the Guinness Book of Records about a cane toad from Proserpine, QLD. Gerty allegedly weighed 3 kilograms (6.61 pounds) and was raised on a diet of beer. Aftder Gerty died the Guinness adjudicators rejected the record claim due to lack of evidence.

· Cane toads are extremely hardy and have been observed hopping out of bush fires, climbing out of freshly tamped hot tar and hopping away after being impaled or run over.


· In 2008, a cane toad named Spew survived for 40 minutes in a dog’s stomach after being swallowed whole. Dog and toad were unharmed.


· The RSPCA suggests that the most humane way to kill a toad is refrigeration. To do this, put on a pair of gloves and catch the toad. Put the toad in a plastic bag or container, seal it up, then refrigerate 12 hours. The toad will go to sleep. Next, put the bag into the freezer for at least 24 hours and the toad will die painlessly.


· At one point the RSPCA recommended dispatching the toads humanely by smearing them with hemorrhoid cream. This method did not gain popularity.


· A Queensland University academic estimated that more than 200 tons of cane toad flesh is squelched on Queensland roads each year.


· Prince Charles and Lady Diana were given a book bound in cane toad skin leather as a wedding present. Charles, in his “thank you” letter, said it would give them much pleasure in their married life.


· Toad venom is so potent that it will quickly dispatch with a 9 Foot Crocodile.


· Vets have recorded cases of clever domestic dogs consistently licking the toads in controlled doses in order to enjoy the effects of the venom.

 

FOR FURTHER INFORMATION ON CANE TOADS PLEASE SEE:-

 

www.canetoadstheconquest.com