(单词翻译:单击)
Pigs are not native to North America. They were first introduced to California by Spanish and Russian explorers and settlers many centuries ago. In the early times, pigs were allowed to wander freely and search of food. This practice also allowed many pigs to escape from farms and live in the wild, which became a problem.
猪并非是美国的本土物种。多个世纪前，西班牙和俄罗斯的探险家和定居者首次将它们引入加利福尼亚州。早期，猪被允许自由游荡和寻找食物。这种做法也让许多猪逃离农场，在野外生活，而这成为了问题。
In fact, as one of the most damaging invasive species on the continent, wild pigs caused millions of dollars in crop damage yearly. They also harbored dozens of diseases that threaten both humans and farm animals. Forest patches with wild pigs have been found to have considerably reduced plant and animal diversity.
事实上，作为非洲大陆最具破坏性的入侵物种之一，野猪每年造成数百万美元的农作物损失。它们还携带着数十种威胁人类和农场动物的疾病。有野猪生活的森林斑块被发现植物和动物多样性大幅减少。
In addition to either eating other animals or their food supply, wild pigs damaged native habitats by reaching up crosses and rubbing on trees. Their activities may also create opportunities for invasive plants to colonize these areas. Wild pigs will eat almost anything containing calories. Mice, deer, birds, snakes and frogs are among their victims.
除了吃其他动物或它们的食物供应，野猪还通过杂交和在树上摩擦来破坏当地的栖息地。它们的活动也可能为入侵植物在这些地区定居创造机会。野猪几乎可以吃任何含热量的食物。老鼠、鹿、鸟、蛇和青蛙都是受害者。
They can also harm other wild species through indirect competition rather than eating them or shrinking their food supply. On one particular United States island, wild pigs themselves became an attractive food source for a species of mainland eagle. Eagles began breeding on the island and also feeding on a species of native fox. The foxes were almost wiped out completely.
它们也可以通过间接竞争而不是吃掉或减少食物供应来伤害其他野生物种。在美国一座小岛上，野猪本身就是一种大陆鹰的诱人食物来源。鹰开始在岛上繁殖，它们也以一种本土狐狸为食。这导致狐狸几乎被彻底消灭。
Questions 16 to 18 are based on the passage you have just heard.
请根据刚才所听文章回答16至18题。
Q16. What do we learn about early pigs in North America?
问题16. 有关北美早期的猪，我们了解到了什么？
Q17. Why are wild pigs a threat to humans?
问题17. 为什么野猪对人类构成威胁？
Q18. What does the passage say about the native foxes on a U.S. island?
问题18. 这篇文章提到了美国一座岛上本土狐狸的什么情况？
