Not in my backyard you don't!

A story on the BBC last week tells us that in the US domestic cats are killing billions of birds and other wildlife each year.  It's primarily stray and feral cats, but pet cats as well.  This raises lots of questions.

Normally, predator populations are kept to well below the size of their prey populations, for the simple ecological reason that if there are too many predators they'll decimate their prey....and thus eventually their own population for lack of food.  If the theory of population ecology is accurate, as it seems to be, there are natural predator-prey population size relationships that maintain this aspect of the natural food chain in any area.

Cat catching a bird; Pablo Picasso, 1939

Of course, here the story is different.  We breed and feed domestic cats and dogs.  Dogs may be too clumsy to catch backyard or park species, to their eternal frustration, but not cats.  Their instincts to sneak and pounce are clearly very effective.  Since their population is not dependent on prey (except perhaps on some farms), their population is not kept down by lack of food.  Instead, their hunting effectiveness can eliminate prey species without threatening the survival of the predator.

So, cute as they are, as often as we can, what we say to our neighbors' cats is:  not in our backyard you don't!