(This article It was first published in Forskning.no)
Cats hunt more than 2,000 different species around the world. In a new study published in the journal Nature Communications, researchers combined knowledge about what cats eat from several hundred studies from many countries around the world.
The result is a very long list of prey. About 17 percent of species are threatened in one way or another and are, for example, on the IUCN Red List.
It doesn't just catch pests
The cat is a special predator.
It is a domestic animal that has lived and coexisted with humans for more than 9,000 years, while it is also a predator that has retained ancient hunting instincts, according to the researchers behind the new study.
They also accompany us humans wherever we move around the world, but the cat does not only hunt pests such as mice and rats.
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Cat coffin from ancient Egypt. As is known, cats had a very special place in the Egyptian worldview, and thousands of mummified cats have been found. Image: Metropolitan Museum of Art
The researchers who conducted the new study describe cats as an invasive species on a global scale. Cats can therefore pose a threat to many different species in many different places in the world.
Researchers call the cat a versatile predator: a generalist.
– As I see it, the most important thing here is to document how many different species the cat has taken, says Erlend Nielsen to forskning.no.
“It's interesting to see how broad the range of the diet is,” he says.
He is a researcher at the Norwegian Institute for Natural Research (NINA) and a professor at Nord University. He helped create a comprehensive report on what kind of risks cats pose to other animals in Norway. This report from the Scientific Committee on Food and Environment (VKM) was launched in November 2023.
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Ordinary and extraordinary
In the international collective study of what cats eat around the world, researchers documented that cats eat 2,084 species. The most common species eaten by cats is not surprising when reading: the common mouse, black rat, brown rat, and house sparrow were among their most common prey.
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The European hare was also a common species to be found in studies.
Reptiles such as geckos and other small lizards are also universal cat favorites. Insects are also an important part of a cat's diet.
To find out, the cohort study studied stomach contents and analyzed stool. This gives a picture of what the cat actually ate. These could be animals that have been hunted or eaten by animals that have already died.
The total species were 981 birds. Thus birds were the largest prey group. About seven percent of these species were threatened in some way—everything near-endangered in the wild. An example of an extinct species eaten by cats is the Hawaiian crow.
It lived naturally on the islands of the Hawaiian Archipelago, another discovery in the group's studies.
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In general, the islands have the most endangered species. Here cats could also threaten more vulnerable species, compared to the mainland, according to the researchers.
Hawaiian crow in the open. It is now extinct in the wild, according to the International Union for Conservation of Nature. Photo: U.S. Fish and Wildlife Service
A huge selection – from beetles to cows (!)
Researchers document that cats eat animals within a wide range in size.
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They eat a lot of small insects, small hummingbirds weighing a few grams, and even much larger animals. The researchers highlight, among other things, the green sea turtle, whose usual body weight exceeds 130 kilograms.
But there are also cases when cats ate cows. This is likely an example of a cat eating a cow that was already dead, or it somehow possessed a very young individual. The same applies to other large animals.
There are examples of cats eating larger animals in Norway as well. The Scientific Committee on Food and Environment report states that cats may have taken deer calves, but cats do not pose a significant threat to these animals anyway.
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The roe deer calf was likely sick and very weak when it was picked up by the cat, says Erlend Nielsen of the NINA Research Institute.
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All kinds of weird
It is unclear exactly why a cat has such a wide range of diet.
– As a domestic animal, it has a different behavior from wild predators, says Erlend Nielsen.
He stresses that this is just speculation, but a wild animal may have to eat what is available to it to survive. A cat can select its prey to a greater extent.
– There is a hunting instinct, and a cat is an animal that wants to find food on its own.
Another surprising finding is that new studies on cat diet are constantly documenting new species that cats eat.
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– There are likely more species that have not yet been documented, Nielsen tells forskning.no.
Researchers are clear that new studies will likely continue to fill out lists with species. There is also a bias in research subjects, with a relatively large proportion of studies coming from Australia. North America and Europe are also over-represented, compared to Asia, Africa and South America.
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In Australia, there has been a lot of focus on what kind of damage the cat is causing to local wildlife, since the cat is an exotic animal in the Australian fauna. Australia also has a lot of guidelines, laws and regulations to not disturb the animal and plant life too much.
Cats in Norway
It is also documented that cats take a wide range of species found in Norway, says Erlend Nielsen.
Assessing the risks that cats pose to Norwegian nature, researchers estimate that there are between 690,000 and 870,000 domestic cats in Norway. They take between 21.3 and 68.9 million prey each year.
The largest concentration of mammals is found here, with birds coming in second place.
Globally, cats eat many species of small lizards. Image: Shutterstock/NTB
Erlend Nielsen says there is evidence that cats have taken several red-listed species. According to the Norwegian report, we are talking about bats and different bird species, but they did not calculate the total percentage of Red List species captured by cats in Norway.
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The report concludes, among other things, that cats in Norway pose the greatest risk to so-called vulnerable birds in densely built areas, or where many birds congregate.
reference:
Lepczyk et al: Global synthesis and evaluation of diets for free-ranging domestic cats. NatCom, 2023. DOI: 10.1038/s41467-023-42766-6. summary
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