4.
Choose the words and complete the passage.
Australia's worst pests(害虫)are the rabbits, 1by
a settler who released 24into the wild for sport hunting. In less than 100
years, the rabbits grow into the millions of ones, leaving large areas of land
looking like the surface of the moon due to thousands of rabbit caves. The
spread of the rabbits in Australia was the fastest of all animals in the world,
The spread of the rabbits'2in 1950 cut the number, but it was not
until 1997 when the spread of another disease targeted the pests that the
number was finally brought under control. Farm losses due to rabbits today
still3 a
surprising total A $ 200 million(US$ 112 million)a year.
The
European red foxes, also released for sport hunting, are growing and eating
sheep flocks, costing farmers A $ 40 million(US $ 22.4 million)a year. The State of
Victoria4a A$10(US$5.6)prize for each fox tail and has gathered 25. 000 in a few months.
Foxes are
one of the biggest threats to wildlife in Australia. Foxes kill thousands of
lambs, birds and native wildlife.
Now the
government is paying more attention to this problem. Scientists5 that they should import some wild dogs, which
are natural enemies of rabbits and foxes, But how to control their6is
also a problem. Scientists say they will not take any big action until they are
sure not to bring another ecological(生态的)problem.