Yijes. It appears I have harboring a couple of cold-blooded killers:
In a report that scaled up local surveys and pilot studies to national dimensions, scientists from the Smithsonian Conservation Biology Institute and the Fish and Wildlife Service estimated that domestic cats in the United States — both the pet Fluffies that spend part of the day outdoors and the unnamed strays and ferals that never leave it — kill a median of 2.4 billion birds and 12.3 billion mammals a year, most of them native mammals like shrews, chipmunks and voles rather than introduced pests like the Norway rat.
[. . .]
More birds and mammals die at the mouths of cats, the report said, than from automobile strikes, pesticides and poisons, collisions with skyscrapers and windmills and other so-called anthropogenic causes.
My cats stay indoors, though, so they ain't adding to the body count much. I think their instincts may have dulled a little -- they can't even seem to handle the one tiny little mouse that found its way into my house.