People who allow their cats to roam outdoors are actually breaking European rules on nature protection, Trouw reported on Wednesday.

A paper by Tilburg university environmental law professors Arie Trouwborst and Han Somsen in the Journal of Environmental Law argues that the domestic cat (Felix Catus) is posing a serious threat to some 370 species in the Netherlands.

Under the European Bird and Habitat Directives countries have a legal obligation to protect wildlife, so allowing cats to roam and kill is illegal, the researchers say.

‘If you would want to take the Dutch government to court for neglecting its legal duty you would stand a good chance of winning,’ Somsen told the paper.

Some 140 million animals, from birds to bats, reptiles and fish, are thought to be killed annually by cats in the Netherlands and half the killings are carried out by cats with owners.

The Netherlands is home to between two and three million cats and some 10,000 feral cats and strays.

Cats do damage to wildlife even without killing, the researchers said, because they cause stress to birds which will then have fewer young and transfer diseases.

‘It may not be people’s intention to harm wildlife but that is what they are doing when they are opening the cat flap, and it’s happening on a large scale,’ Somsen said.

Legal conclusion

The researchers said the cat is the only animal that leaves the house on its own and that it should be kept indoors or within the confines of a garden.

Measures to that effect are sure to be on the way, they said. ‘The legal conclusion is watertight. The environmental damage is too great to continue to make a legal exception for the domestic cat.’

However, the European Commission does not appear to be impressed. The Dutch EU bureau said on Twitter that the Commission will not be asking cat owners to keep their pets on a lead.

‘According to our information, cats are not the biggest threat to biodiversity,’ the statement said.

Maak dat de kat wijs! De Commissie gaat katteneigenaren niet vragen om hun dieren aan te lijnen. 🙀 Katten zijn volgens onze informatie niet bij de grootste bedreigingen voor de #biodiversiteit. — Europa in Nederland (@EUinNL) November 27, 2019