Former President George W. Bush's dog Barney has gone to that great kennel club in the sky. I'll bet Barney died smiling. He lived to see the day when humans finally acknowledged that cats are a menace.In fact, government-affiliated scientists have produced statistical proof of feline perfidy, in a new study showing that cats stalk and kill 2.4 billion birds and 12.3 billion mammals in the United States each year, give or take a few billion.This "kill rate" is two to four times higher than previously believed, and worse than that attributable to windmills, cars and other "anthropogenic" threats.The victims include not just rats and mice but also songbirds, chipmunks and other valued wildlife species, according to The New York Times.Feral -- "stray" -- cats, which number 80 million or so, are the main culprits, the study concluded. But the nation's 86.4 million domestic cats account for about 29 percent of cat-on-bird killings and 11 percent of cat-on-mammal slaughter.Scientific though it may be, the report is not irony-free. It brands cats an "invasive" species, imported to North America by humans and unchecked by natural predators. Yet three of the 11 most-victimized bird species in the study are also invasive: the house sparrow, the rock pigeon and the European starling.In my book, that means every time a cat takes out one of those winged pests, it's a case of justifiable avicide.But never mind that. "Scientifically sound conservation and policy intervention is needed to reduce this impact," the study notes.I don't think they're talking about federally subsidized tummy rubs.Some environmentalists think that euthanasia may be the only way to prevent an uncontrolled killer-cat population from ravaging wildlife, given the absence of a natural predator.Others recoil at mass cat-killing to cure mass bird-killing. Some animal welfare advocates think the solution is to sterilize feral cats and then release them. A variant is to rehabilitate freshly neutered or spayed stray felines as "working cats," who keep rats out of human hangouts, including -- in one actual case -- a Los Angeles police station.But it has been rightly noted that the life of a stray is pretty miserable, what with the constant threat of cars and disease. Useful as mousers may be, the supply of working cats will probably always exceed demand.Our frontier ancestors surely would have marveled at a society so civilized and affluent that it can indulge in such quarrels. I don't have a dog in these fights. My only semi-serious point is that it is much easier to declare one's concern for animals, their welfare and even their rights than to act on that concern in a logical, consistent manner. When it comes to moral reasoning about animals, we're all sort of chasing our tails.Science can help describe issues and inform debate. But it still takes human judgment, leavened by instinct and intuition, to balance the interests of the various species affected -- homo sapiens included.At least domestic cat owners can help by keeping their pets inside, The Times suggested. But even that innocuous recommendation could be a prescription for cruelty, depending on your perspective.Mietzi, our long-haired Norwegian forest cat, is not allowed out. She spends hours each day crouched against the window, glaring at birds and squirrels as they impudently hop by.Her tail twitches. How she longs to spring at her prey, as her ancestors did among the pines of Scandinavia!But the glass -- that incomprehensible transparent hardness -- frustrates her every time.Mietzi feels better when we feed her tuna, ground up and packed into a little can with a convenient pop-top lid. I'm pretty sure it's dolphin-safe.Charles Lane is a member of The Washington Post's editorial board.