Gareth Morgan says your cat “is actually a friendly neighbourhood serial killer”.

You know what animal makes a good pet? No animal.

Dogs will bite you to death and then eat your corpse. Snakes will asphyxiate you, escape, infest the countryside, and eat all its mammals.

Pet parrots perpetuate a trade that upends ecosystems, and hamsters pass you dangerous zoonotic diseases.

Cats kills for pleasure ... Gareth Morgan.

Cats kills for pleasure … Gareth Morgan. Photo: Bill Kearns

But perhaps the worst pet of all, environmentally speaking, is a cat.


Domesticated cats started out as parasites on human civilisation. Unlike other species, and admittedly to their credit, they domesticated themselves.

When humans started growing grain, the crops attracted rodents that attracted cats. Wild cats evolved into housecats, and they were quite useful for thousands of years, killing disease-ridden rats and mice and protecting our food stockpiles.

But now that we have industrial farming, reliable food storage, and mostly mouse-proof houses, cats are mere parasites again.

Playful and often affectionate parasites, sure, and adorable when young, but a scourge on the landscape.

An economist in New Zealand named Gareth Morgan (who is the father of Sam, the founder of the online auction business TradeMe) has made the logical and quite correct case that Kiwis should eliminate its cats to protect its endangered birds.

He means “elimination” in the most humane way possible: Existing pets should be spayed and neutered and allowed to live out their lives, but no new cats should be allowed to be born or imported.

He is not advocating that people poison feral cats. Nor does he say people should shoot them, as particularly avid birdwatchers have done. That would be really wrong.

Morgan points out that your cat “is actually a friendly neighbourhood serial killer.” He may sound like some wretched, obsessed character, but his Cats To Go project isn’t meant as a caricature of environmentalism.

He’s asking people to pledge to neuter their cats, keep them indoors, and not get any new ones.

Cats are a globally invasive species. They kill millions of birds each year.

Cats are particularly damaging in island ecosystems that are home to species found nowhere else on earth.

A lot of island birds and mammals evolved in the absence of cat-size predators. They nest on the ground and have no defenses against an invasive species that plays with and then decapitates its victims.

Cats have endangered or caused the extinction of bird species in Hawaii, Australia, the Chatham Islands and New Zealand, among others.

Morgan points out that 40 per cent of New Zealand’s land birds are extinct, and 37 per cent of the survivors are endangered.

Humans are responsible for most modern extinctions, whether through hunting, habitat destruction, introduction of invasive species or other environmental disruptions.

If we give up or at least contain our cats, wild animals will have more of a chance.

Laura Helmuth is Slate’s science and health editor.