Japanese study of TNR feral cat colony tells us that cat food is their main food supply

This study came to the conclusion that TNR volunteers managing a feral cat colony on Tokunoshima Island might cause what the scientists call ‘hyper-predation’ of local native species. What they mean is that the cats are helped by people feeding them. They think that by feeding the cats there is more predation of native species. They are not sure though as it is a suggestion to be studied further.

Japanese feral cat with large rat in his mouth
Japanese feral cat with large rat in his mouth on the Japanese island of Tokunoshima. Photo: by the author of the report Y. Watari, Forestry and Forest Products Research Institute.
Two useful tags. Click either to see the articles: Toxic to cats | Dangers to cats

However, the chart below shows that food put down by people (artificial sources) was by far the most important source of food for these feral and stray cats.

“..that cats themselves depend on human-derived resources..Overall, our study indicates that invasive free-ranging cats depend on anthropogenic feeding.”

TNR feral cats mainly rely on cat food
TNR feral cats mainly rely on cat food. Chart from “Predation on endangered species by human-subsidized domestic cats on Tokunoshima Island” by Yuya Watari and others.

‘Anthropogenic’ means it comes from the activities of people, in this instance volunteers and cat lovers who are involved in the TNR program and who feed the cats. There may be others too who feed the feral cats.

My interpretation of the report is different to that of the scientist who wrote it up. Their general conclusion was as mentioned above namely that human feeding of feral cats enhances their feeding on prey. I disagree for 2 reasons: TNR reduces the number of feral cats or stabilises their population size which should in the long term reduce cat predation. The study author admits that the TNR program has ‘been achieving some degree of success’ in this regard.

Secondly, if TNR volunteers did not put down food the cats would be more likely to wander onto neighbouring farmland or the woods in search of prey. Wouldn’t that mean that more animals are eaten by the colony’s feral cats?

The study is poor in my view. It feels biased. I sense the author wants to trap and kill feral cats which is the poor, unsuccessful alternative to TNR. And there is too much guesswork.

There is another point worth making. Camera trap photos shows one cat with a large Ryukyu long-haired rat in their mouth (see photo at the top of the page). And in another the prey is an Amami rabbit which is even larger. It is unusual to see photos of such large prey in the mouths of feral cats. It indicates that feral cats can help to keep down rat numbers but instinctively the cats will eat the easiest to find food which is invariably cat food if it is supplied by people. Also it depends on the individual cat. Some cats are scared of large rats.

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Useful tag. Click to see the articles: Cat behavior

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