What does an outdoor cat do all day? A study of more than 900 house cats shows when they kill small birds and mammals, their influence is concentrated in a small area, having a bigger effect than wild predators (食肉动物) do.
Roland Kays, a scientist at North Carolina State University and his colleagues collected GPS data from cats in six countries. “These cats are moving around their own backyard and a couple of their neighbors' backyards, but most of them are not ranging very much further,” Kays said. “So initially I thought, 'Oh, this is good news. They're not going out into the nature preserves.’”
Then Kays took how much cats kill m that small area into consideration. Some cats in the study were bringing home up to 11 dead birds a month, which doesn't include what they ate or didn't bring home.
“It actually ends up being" a really high rate of predation," Kays said. He calculates that cats can have 4-to-10 times the influence of a wild predator. Native predators, like jungle cats, also kill a lot of small animals, but their influence is spread out over a larger area. One study indicates that house cats kill billions of birds every year.
“The simplest thing to do is to keep your cat indoors,” Kays said.
For those who refuse to keep their cats inside, there are potential options. St. Lawrence University associate professor Susan Willson went looking for one. She found a special brightly colored collar online. “The whole idea is that the bird will be able to visually see the cat creeping (爬) up on it before the cat attacks it,” she said. Willson tested the collar on both her cat and dozens of others. It greatly reduced the number of birds the cats brought home.
“I'm not saying these collars can make a significant difference in the massive bird death that we're seeing,” she said. “But each individual bird that somebody in their backyard is not finding dead, I think matters.”
8. Why does Kays say “this is good news”?
A.House cats can be tracked by GPS. |
B.House cats won't kill birds in large numbers. |
C.House cats are protected from wild predators. |
D.House cats feel comfortable in their own backyard. |
9. How do wild predators differ from house cats in terms of killing animals?
A.They prefer to attack larger animals. |
B.They kill 4-10 times the number of house cats. |
C.Their victims are distributed in a bigger range. |
D.They kill less than house cats on a monthly basis. |
10. What can we infer from the passage?
A.Birds can't sense the danger when cats attack them. |
B.Willson considers keeping her cat inside a good idea. |
C.The only way to protect birds is to keep them indoors. |
D.The colored collar can be a sign of potential danger to birds. |
11. Which word can best describe Willson's attitude to using collars to save birds?
A.Concerned. | B.Positive. |
C.Doubtful. | D.Cautious. |