美国科学60秒 SSS 2013-02-01

（单词翻译）

 　　Beneath its adorable exterior¹ is your cat hiding the heart of killer².Researchers now estimated that each year domestic cats kill billions of birds and mammals in the United States alone.The report is in Nature Communications.We already knew that domestic cats can wreak³ havoc⁴ on islands causing 14 percent species extinctions and ranking as one of the worlds 100 worst invasive species.But now scientists have reviewed previous study to find just how much damage cats do on the mainland.Cats kill some 1.4 to 3.7 billion birds and 6.9 to 20.7 billion small mammals in the US each year.This numbers mean that felids may be the biggest human related cause of death for American birds and mammals.And cats had prong need of species which can cause major ecosystem⁵ damage.The worse feline⁶ killer and those without owners and reducing feral cat populations is a ongoing⁷ problem.But you can still reduce the impact of domestic cats by keeping your pet indoors.Thus leaving the neighborhood a little less red in tooth and claw.