While there were no objections to the 1,786 other species listed in the database, Solarz told The Associated Press on Tuesday, the public voiced their anger at the new entry.
The scientist explained to AP that this could be due to a false impression from a few media reports that the Institute was calling on feral and other cats to be euthanized.
Solarz defended the cat's addition to the list and added the criteria for an invasive alien species "are 100% met by the cat," and in a TV appearance on an independent broadcaster, TVN claimed cats kill about 140 million birds in Poland each year.
Cats have been classified as "invasive alien species" by Polish Academy of Sciences due to damaged caused by birds and other wildlifeiStockphoto by Getty Images
But that has not stopped the criticism as Dorota Suminska, a veterinarian and author of the book "The Happy Cat," who also appeared in the TV segment where she disputed Solarz's conclusion and noted other factors that can kill birds such as declining biodiversity, pollution, and urban buildings.
Due to people getting the wrong end of the stick, the Institute has reassured the public that it is "opposed to any cruelty towards animals," and added the classification was in line with European Union guidelines.
In turn, it also argued that cats are technically "alien" to Europe because the species was domesticated approximately 10,000 years ago in the civilisations of the ancient Middle East.
With the cat's addition to the list, the Institute insisted it was advising cat owners to limit the time their pets spend outdoors during bird breeding season.
Despite being a dog owner, Solarz says he's feline fine about the newly listed "invasive alien species."
"I have a dog, but I don't have anything against cats," he said.
Additional reporting by AP.
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