All NPR News

The murderous creature you live with is a murderous creature, a study confirms

By Manuela López Restrepo

Published December 12, 2023 at 5:22 PM EST

More scientific evidence has surfaced to show that while Mittens may be your sweet angel, letting her roam outside is also a big threat to biodiversity.

Who are they? A single woman's life companion. A dog lover's scapegoat. They are the freaky little furry guys we know as the cat.

Here's my son. His name is Martin. He's an apartment cat. He yells at me all day. He just figured out how to slam cabinet doors when he wants my attention.

What's the big deal? Scientists reviewed more than 100 years' worth of scientific studies to gain a better understanding of which animals free-ranging cats will prey upon or scavenge.

The resulting paper, published in Nature Communications, found that free-ranging cats (including domestic and feral) will eat 2,084 different species of birds, mammals, reptiles, amphibians and insects. There were even cows on that list, though they were probably the result of scavenging rather than hunting.
The list of creatures cats have chowed on includes 347 species of conservation concern, including Newell's shearwater, green sea turtles, the northern bobwhite quail and the little brown bat.
While cute, cats are skilled predators, so much so that they've been documented as a major threat to the biodiversity of bird species in North America.
They're also linked to the extinction of more than 60 species worldwide.
Despite the problem globally, a separate report in 2022 found that "cats are either unmanaged or managed using scientifically unsupported and ineffective approaches ... in many jurisdictions around the world."

Want more on animals? Listen to Consider This on how when disaster hits, dogs come to the rescue.

What are people saying? Christopher Lepczyk is a wildlife ecologist at Auburn University and a co-author of the paper, and spoke with NPR to help expand on the paper's findings.

On the most surprising aspect of the study:

Just the amount of different insects and invertebrates that they are eating in their diet. We know that they eat insects. That wasn't necessarily new, but we didn't really have an idea that they were eating so many things. And I think our concern there is that most scientists that have done these studies in the past were not really looking for insects and they're not taxonomists trained to understand insects.

I think also just the totality, we really at some point, we started to get more and more individual species picked up in our study, and it kind of seemed almost endless.

On the species that are most vulnerable to cats:

When you see something like a whole lot of juveniles hatch out of eggs, it's an opportunity for predators to obtain pretty easy ... prey. And so I think if we contextualize it that way, it's probably not surprising.

On misconceptions people have about outdoors cats in their own environment:

A lot of people live in urban areas or they may not think that there's a lot of wild animals living in the location where they live.

That doesn't mean a cat has no effect on the environment. You know, a lot of times we really don't observe what cats eat, but that doesn't mean they're not actually eating something outside.

So, what now?

If you want to follow the science, then the only hunting your cat should be doing is that cockroach in the bathroom you're too scared to catch yourself.
Lepczyk's report didn't make any recommendations for dealing with the issue. Instead, he told NPR the purpose of the paper was "really to just help provide that information to ecologists, to practitioners and to policymakers." However, Lepczyk said he keeps his cats indoors – and points to evidence that indoor cats are both healthier and live longer.
Apparently a colony of wild cats is called a clowder. I can barely handle one.
Here's an obligatory second Martin pic because my son deserves to be famous:

Learn more:

Christopher Intagliata contributed to this report. contributed to this story