2020托福听力练习：美国政府拟用无人机发射疫苗保护濒危雪貂（下载）

　　A recent headline on the Web site theverge.com got a lot of attention on social media. Because each new phrase seemed to take the message in an unexpected direction. The headline read: U.S. government plans to use drones to fire vaccine-laced M&Ms near endangered ferrets.

　　Some background. Black-footed ferrets have been on the endangered species list since 1967. Only about 300 were known to be alive in the wild at the end of 2015. They tend to live in the Great Plains and the West. Because they love to eat prairie dogs, which tend to live in the Great Plains and the West. Unfortunately, prairie dogs often harbor fleas, and fleas can carry the plague. Yup, that plague, the so-called Black Death that killed millions in Europe in the 14th century.

　　So ferrets suffer when fleas cause a plague outbreak in prairie dogs, either because the ferrets also catch the disease or because the prairie dogs die and the ferrets go hungry. Officials have tried vaccinating individual ferrets and they've tried treating prairie-dog burrows with flea-killer. But neither method is particularly efficient.

　　And so the U.S. Fish and Wildlife Service is preparing a study for September in the UL Bend National Wildlife Refuge in Montana. The viral headline was incorrect about the M&Ms, but otherwise, yes, aerial drones will shoot vaccine-laced pellets designed to be irresistible to prairie dogs. The drone delivery system should quickly spread the vaccine-carrying goodies over a wide area so that lots of prairie dogs gobble them up—thus making the prairie dogs available to be gobbled up, safely, by the endangered ferrets.

　　And so everybody wins. Except for the prairie dogs that get eaten. And the Yersinia pestis bacteria that cause plague. Well, that's it for me, I've droned on long enough.