The Cat That Kills On A Full Stomach
House cats kill around 2.4 billion birds a year in the United States alone, and a classic experiment showed they will leave a bowl of food to kill a rat, then go back to eating. Hunting and hunger run on separate wires.
The Predator With a Bowl at Home
A house cat kills a bird with a single bite to the back of the neck, then often walks away and leaves it on the lawn. It is not hungry. It almost never is. That is exactly what makes the domestic cat one of the most destructive predators on the planet.
Two Billion Birds a Year
In 2013, researchers Scott Loss, Tom Will and Peter Marra published the first systematic estimate of cat predation in the United States in Nature Communications. Free-ranging domestic cats kill somewhere between 1.3 and 4 billion birds a year, with a central estimate around 2.4 billion, plus 6 to 22 billion small mammals.
That makes cats the single largest human-linked cause of bird deaths in the country, ahead of collisions with vehicles and windows. Most of the killing is done by un-owned and feral cats, but owned pets that roam outdoors contribute too.
Sixty-Three Extinctions
The damage is not only local. A 2016 review in PNAS by Tim Doherty and colleagues tallied the species lost to invasive predators worldwide. Cats were implicated in the extinction of at least 63 species: 40 birds, 21 mammals and 2 reptiles. On islands, where prey never evolved alongside a ground predator, a handful of cats can erase a species outright.
The Experiment With the Rat
The most revealing detail comes from a small 1976 experiment by Robert Adamec. Cats were given their preferred food and allowed to eat for 45 seconds. Then a rat was released into the room.
In every case, the cat stopped eating, crossed the room, leaped down and killed the rat. Then it carried the rat back to the food dish and went on eating its original meal.
The cat did not hunt because it was hungry. It hunted because prey moved. In cats, the drive to kill and the drive to eat are wired separately, which is why a well-fed pet with a full bowl at home still comes back with a bird.
Sources
- nature.com: The impact of free-ranging domestic cats on wildlife of the United States (Loss, Will & Marra, 2013)
- pubmed.ncbi.nlm.nih.gov: The interaction of hunger and preying in the domestic cat (Adamec, 1976)
- pnas.org: Invasive predators and global biodiversity loss (Doherty et al., 2016)
- smithsonianmag.com: The moral cost of cats
