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Environment: Attack of The Killer Cats

3 minute read
Leon Jaroff

While fond of his cat, British biologist Peter Churcher looked askance at its practice of dragging small mammals and birds into his Bedfordshire house and devouring them under the kitchen table “to the sound of crunching bones.” One of Churcher’s associates, John Lawton, a professor of community ecology at the University of London, was similarly impressed by his own cat’s predatory pursuits. With the natural curiosity of true scientists, they decided to look further into the depredations of felines. If all the domestic cats in Britain caught as much prey as theirs did, the two men reasoned, they could be having a “very significant” impact on the environment.

Hyperbole? Not at all. Writing in the July issue of Natural History, Churcher and Lawton estimate that Britain’s 5 million house cats wreak an annual toll of some 70 million animals and birds.

In reaching this astonishing conclusion, the intrepid investigators used only the most rigorous scientific methods. Choosing Churcher’s small village as their test site, they conducted a feline census and found that 78 cats resided in the community’s 173 houses, “a slightly higher incidence of cat owning than in Britain as a whole.” Owners of 77 of the cats agreed to cooperate. Each was given a supply of consecutively numbered polyethylene bags labeled with his cat’s code letter and asked to store whatever was left of any prey his pet brought home.

For a full year the scientists made weekly rounds of the village, collecting bags and identifying the remains. If the cat had consumed the entire catch, the victim was simply recorded as an “unknown.” Otherwise, the identification process was simple, the scientists report, although “initially — the study began during the summer months — it was rather smelly.” Surprisingly enough, they write, “the villagers were much less squeamish than we had expected.” In fact, some went about their assigned task with great gusto, placing their cats’ trophies in home freezers to await collection.

Tallying and analyzing their data at the end of a year, the investigators found that the cats had claimed almost 1,100 items of prey, 64% consisting of small mammals: mostly wood mice, field voles and common shrews, interspersed with an occasional rabbit, weasel or pipistrelle bat. The remaining victims, all birds, included sparrows, song thrushes, blackbirds and robins.

Delving further into the sparrow toll, which accounted for 16% of the total feline catch, the scientists concluded that from a third to a half of all sparrow deaths were attributable to cats. Extrapolating these figures, they estimated that cats kill at least 20 million birds a year in Britain. “Yet,” write the authors indignantly, “we are supposed to be a nation of bird lovers, many of whom keep cats but still castigate bird hunters and trappers on the continent of Europe.”

Impressive as these statistics are, the scientists note, the carnage may be even worse. They cite an American study indicating that house cats bring only about half their victims home.

Will cat fanciers find these conclusions unsettling? Evidently not. When the authors’ work was published earlier in a scientific journal, including the fact that a few Bedfordshire cats had each contributed as many as 100 items of prey to the study, they received letters from other cat owners boasting of their own pets’ prowess. The record, they report, is currently held by a cat from Dorset that dragged in more than 400 little creatures in one year. The scientists are aghast. “These proud owners,” they report, “seem quite unperturbed by the slaughter.”

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