Indoor Cats vs. Outdoor Cats
Ruthless killing machines, but oh so cute! Sierra's contributing writer Dashka Slater bravely ventures into the fraught subject of the environmental effects of cats (and dogs!) in the current issue of the magazine, below. For another charming take on the same subject, see the short video by Caroline Paul and Wendy MacNaughton at bottom (with thanks to @brainpicker).
ON THE ONE HAND. . . Soft, whiskered, and purring, your cat may not look like a ruthless killing machine. But a study from the Smithsonian Conservation Biology Institute indicates that more birds and small mammals die via Fluffy's claws than via cars, pesticides, poisons, colliding with windows, or any other human cause. The study found that cats kill between 1.4 and 3.7 billion birds each year, along with 6.9 to 20.7 billion mammals. While feral cats are responsible for the vast majority of the carnage, even well-fed house cats kill an average of 2.1 animals every week they are outside. Worst of all, cats seem to prefer killing native species over icky invaders like the Norway rat.
ON THE OTHER . . . Dogs are worse. Catering to a medium-size dog's carnivorous instincts requires an ecological pawprint twice as large as it takes to build and fuel a large SUV. Worse, once Fido is sated, he has plenty of energy to chase birds, disrupt their nesting sites, exhaust them during migration stops, or kill them outright. A single dog killed more than half of the members of a New Zealand kiwi colony over the course of a few weeks, while five dogs destroyed Italy's largest flamingo colony in one day. And forget those long walks in the woods: A 2007 Australian study found that walking even leashed dogs in a park led to a 35 percent reduction in the number of bird species found there.