Cats, even well fed by their owners, have a tendency to hunt everything that moves once released outside their home. It's estimated that free-ranging domestic cats kill billions of birds and billions of mammals annually. (source : https://en.wikipedia.org/wiki/Cat_predation_on_wildlife)
We need a worldwide solution to stop cats’ extermination of wildlife. Of course, most people won’t keep their cats inside, so we need something, maybe a device attached to the cat to make its hunting fail.
Do you have ideas to propose?
Edit: Bells work, but only partially.