新托福阅读材料：8WildWaystoCombatInvasiveSpecies（8）
外来入侵物种对本地区的生态系统会造成许多不良影响，科学家们用自己的聪明才智研究出了许多对抗这些“外来侵略者”的有趣方法。接下来我们就一起来看看吧!Combating Cane Toads in Australia
In the 1930s farmers released thousands of poisonous cane toads native to Central and South America into sugar plantations around Cairns, Australia, in the hope that they would rid the fields of beetles. Big mistake. The plan failed, and the toad spread across northeastern Australia, gobbling up native insects and poisoning predators that mistakenly fed on them.
Rick Shine, an evolutionary biologist at the University of Sydney, has been studying the ecology of the invasive cane toad since 2004. "We kept finding all these vulnerabilities," Shine says. For example, the frogs that are native to Australia know how to avoid large, carnivorous ants because they've evolved with them for millions of years. The toads, on the other hand, "have all the wrong responses," Shine says. The baby toads come out of their ponds when the ants are most active. And, when they encounter an ant, rather than hopping away, they freeze.
The researchers found that they could attract meat-eating ants to the ponds where cane toads breed by setting out cat food. When the toads emerge, the slaughter begins: The ants attacked 98 percent of the toads in the first two minutes. Of those, 70 percent died. "Their poison doesn't affect the ants, so they just get creamed in huge numbers."
Shine's lab is also looking at ways to train large predators to avoid eating the toads. Big animals are more likely to grab big toads, which contain the most poison and can cause an instant heart attack. In a recent experiment the researchers laced cane toad meat with a drug that induces severe nausea and fed it northern quolls, cat-size marsupials that sometimes feed on the toads. The tainted meat doesn't kill the quolls, but it makes them very ill. In the field "the ones that have been educated survive very well, the ones that haven't been educated die almost immediately," Shine says. The researchers have seen quoll populations bounce back in some study areas as a result of the training. Shine and his colleagues say the strategy may work for other large predators such as monitor lizards as well.
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