Cats or dogs, another age old question. I wouldn’t be able to answer just one of them. My preference shifts from time to time. Personality wise I’m way more of a cat myself, but if I ever take in a pet, it’ll probably be a dog, and I’m not even sure why. Better company, I’d say. But one who has at least some notion of independence and doesn’t have to have its head on the lap of yours truly all the time. If only there was a dog-cat hybrid (CatDog was sadly only a cartoon). There’s also nothing negative about having a dog, at least if you train it well. Cats on the other hand… That cute little fuzzball of yours?  Might be sleeping a lot and all, but… It’s also a notorious serial killer.

Now, before you all go nuts and start to burn effigies with my likeness, it’s obviously not all cats I’m talking about. You could have a house cat that never runs around in the yard for example. But know that when your cat, when it is able to hunt freely, is probably killing way more than just the rats and mice you hope it’s catching. Besides your pet, the biggest problem is, of course, the humongous amounts of feral cats, especially in cities. So please, sterilize your cats if you’re not planning on having kittens. And if you do wind up with a litter, don’t just go dump them somewhere either. Give them away to people you know who will keep and love them. As for the feral cats already out there, there’s plenty of organizations who try to catch them (in a humane way) and sterilize them before rerealising. It’s not a perfect solution (the murderers are still on the loose), but people might not like your plan of culling every street cat you get your hands on. The end doesn’t always justify the means, but I know of a few cities who really should get rid of at least some part of their feral population as they’ve become a pest problem just as much as rats.

So why do I keep calling cats serial killers and murderers? In the UK, a study claimed that almost 65 million birds are killed by cats. Across the ocean, in the USA, it’s several billion (with an estimated 25 to 60 million feral cats roaming around). I do admit I can’t find an average of how many kills per cat that is, but even conservatively speaking, it would be quite a good number. In addition, there’s enough controversy about the numbers and influences of the cat as a top predator to be cautious about everything you read on the effects of (feral) cats. Cats eat rats too, which in turn can boost the number of birds because the rats themselves are predators of bird eggs. More cats, means less rats, means more bird eggs. And since cats generally don’t eat the eggs, you might have a healthy young population of birds coming up every time. You also have to be mindful of what species of bird you’re talking about (only a very foolish cat would attack a bald eagle), some species are definitely more vulnerable than others. The house sparrow is a bird already on the decline everywhere, and an English study showed that cats could be responsible for about a third of the sparrow’s mortality. The cat’s influence is definitely present there, but it could be worse. Especially on islands cat presence can mean a great deal, which brings me to the next part of the story.

There’s plenty of examples of species, mostly birds, going extinct on islands by the introduction of foreign mammals, mostly due to rats and the obvious cat. Wikipedia gives the examples of the South Island piopio, the Chatham rail and the Auckland merganser. It’s notable that all of these are species from New Zealand, but there’s a good reason for this. To demonstrate: another more famous example, also from New Zealand is the kakapo, a large, flightless parrot. Although not extinct, only 156 individuals are known to still be alive and are kept under close watch on a few islands that are completely devoid of foreign invaders. The cause of their near-extinction is cats, but also dogs, ferrets, stoats and rats. The problem is that the kakapo never had to deal with mammalian predators: it only had to fear other, bigger birds. Birds of prey can’t really smell so when they hunt, they rely on sight. The kakapo just has camouflage itself and sit very still to escape attention. This is why it is flightless, it never had need of functional wings to escape (which would take a great deal of energy too). To get around in the forest, it’s a good climber instead. It also lives nocturnal, since most raptors of New Zealand don’t fly at night. This didn’t work on the mammals, which do use their nose and ears and hunt in the dark. The kakapo was thus an easy prey, because it never figured out it should just run instead of freeze. Fortunately, through conservation efforts, it was saved from completely disappearing. This incapability of the kakapo to deal with new predation tactics is the biggest cause of the disappearance of the other species as well, sometimes in addition with your usual habitat destruction.

There is one other example that I wanted to talk about, one of the most extreme cases of extinction driven by cats. It was, like the kakapo, completely flightless. The Stephens Island wren is named after the island it was last found at (Stephens Island it was called, if you couldn’t guess). The bird used to be found in the whole of New Zealand: Stephens Island wasn’t always an island, otherwise the bird couldn’t have gotten there, what with the inability to fly and all. The disappearance on the main land was probably due to the introduction of the Polynesian rat, brought there by the Maori. After that, the bird was only known to be found on Stephens Island, but by the time scientists were aware of the bird’s existence, it was already too late. The cause? According to some anecdotes, it was one single cat. I hereby nominate Tibbles as to be added to the list of most notorious serial killers, next to H.H. Holmes and Elizabeth Bathory. Tibbles was the cat of the light house keeper, who is the only person to have seen the bird alive, and this only twice. Almost all we know is from data collected by specimens that Tibbles brought in itself, together with other keepers and collectors. Even then, there’s only about 16-18 specimens existing, apart from the collection of bones found of the wrens on the mainland. The whole story of the Stephens Island wren is a bit anecdotal, Tibbles was probably not the only actor in play: it’s known that the island had a bit of a feral cat problem which would easily wipe out a whole population in one winter on such a confined space as an island. Science is the search of truth, not that of a better story.

I’m not here to say that you need to get rid of your cat, or that you should never get one. Just know that it’s perfectly capable of the remorseless killing of a whole species. But, if you already have a cat, you’re probably already very aware of that fact before you read this post. And remember, if you’re a bird, even though it might seem you won’t need it, you better know how to fly. There might be something philosophical there to apply it to the human condition, but I can’t be arsed to find it right now.

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