> a population of feral cats fending for themselves in a unhabited island.

There were numerous examples of this around Australia, there still are some - it's damn hard, nigh impossible, work to remove them via traditional trapping means w/out motivated local inhabitants.

These days we have the Felixer:

https://www.abc.net.au/news/2020-05-29/feral-cat-management-...

https://www.scimex.org/newsfeed/felixer,-the-grooming-trap,-...

Even so, it's unlikely feral cats will be eradicated from Australia anytime soon.