It’s pretty commonly known, and not very startling, that . But the degree to which they eat insects might surprise you.
who for many years have been trying to figure out what feral or outdoor-roaming pet cats eat outside.
When domesticated cats – Felis catus – live freely in the wild or are allowed to hunt outside the homes where their owners live, they are an , which live in every ecosystem of the world except the continent of Antarctica. We wanted to know all of the species they eat – and to what degree free-ranging cats are eating endangered or threatened species.
Examining reams of research
Over the past two decades, we have evaluated hundreds of scientific findings, including searching through and using the keywords “cat predation,” “feral cat,” “cat diet” and “Felis catus.” For each item we found, whether peer-reviewed or not, we evaluated whether it contained conclusive evidence of cat diet or predation. We also reviewed each one’s reference section for additional unique articles or databases pertaining to cat diet and predation, and included those in our search.
Overall, we identified 533 unique publications – books, journal articles, theses and agency reports – that reported specific animal species consumed by cats. Cats’ plant-eating habits are occasionally, but haphazardly, noted in studies, so we did not include them in our analysis.
Our initial work focused on an overall assessment of what free-ranging cats eat around the world. Published in 2023, this paper analyzed the 533 studies on cat diet or predation events published over more than a century and found that of animals, including invertebrates.
Of those 2,100, the listed 347 as “near threatened,” “vulnerable,” “endangered,” “critically endangered” or “extinct” in 2023. Some of the species went extinct during the many decades covered by the data.
Insects and the like
Most of the species cats ate were vertebrates – mostly birds, followed by mammals and reptiles. But the data also indicated that at least 7% of the species cats eat are insects and other invertebrates, particularly beetles, and less frequently crustaceans, arachnids, centipedes, snails and slugs, and millipedes.
Many of the cat studies we reviewed did not report on how many individuals of a given species cats ate, so it was unclear what the total amount of insects was or how many calories cats are deriving from insects.
Invertebrates make up of all terrestrial animal species and are important pollinators, predators and herbivores in virtually every nonmarine ecosystem. Many due to urbanization, habitat destruction, increases in both light and pesticide pollution, and climate change. So we dug deeper into the data to understand .
While a little more than one-third of all the studies we analyzed included invertebrates as part of cats’ diet, most of those failed to identify specific species of invertebrates. But we were able to find identifications of 148 invertebrate species.
Of those, two are considered endangered by the : the (Pternoscirtus aldabrae) in Seychelles and the (Astacopsis gouldi), which can grow up to 13 pounds (6 kilograms). Two others are considered vulnerable: (Deinacrida heteracantha), an insect native to New Zealand that can be about the size of a mouse, and the (Cherax destructor), a freshwater crayfish native to southeastern Australia. One other, the (Arhopalus pinetorum), is listed as “near threatened.”
Effects on populations
We have not found formal research evaluating how cats’ eating habits affect invertebrate populations. And for many species, they are likely not as significant a factor as .
But it’s possible that cats could be significant contributors to the deaths of rare species or in specific locations.
Cats require a , as much as one-third of their daily diet, and .
In many places, invertebrates provide an easy source of food. Whether in an urban backyard or on a remote island, cats are unlikely to turn a blind eye to available prey. And some cats may find it entertaining to chase, catch and eat insects even if they don’t need their nutrition.
A challenge of researching this question is that many invertebrates are relatively small, which makes direct observation in the field harder and can require more analytical approaches in the lab. And they have soft bodies, without distinguishing characteristics that could be easily recognized in scat or stomach contents.
However, molecular technologies can identify species using by animals. Promising new studies are beginning to identify what cats eat by . That research may help explore in even more detail what cats are eating in the outdoors, and how it’s affecting various species and the environment as a whole.
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