You are not wrong. Australia was having a pretty big issue with it.
But, euthanization isn't necessary. It's just more cost effective.
Trap, sterilize, and release/or find homes. They don't live long lives as ferals.
Culling the herd is a bit extreme they don't breed like hogs.
While they don’t breed as fast as hogs, they are no slouches either. I disagree about offing them not being necessary. They cost money AND kill billions of birds. Together that should be plenty of justification for killing them.
“Feral cats—domestic cats that live outdoors and are ownerless—account for $17 billion in economic loss from predation on birds in the U.S. every year, a new, peer-reviewed paper by University of Nebraska-Lincoln researchers finds......There are an estimated 60 million feral cats in the U.S., and as many or more kitties kept as pets. The study reports that cats are responsible for the extinction of at least 33 avian species worldwide, and the felines kill an estimated 480 million birds a year. Besides predation, feral cats also carry and transmit diseases such as cat scratch fever, plague, rabies, and toxoplasmosis. (States require pet cats to be vaccinated).”
As for trap and sterilize, “Many feral cat advocates support trap, neuter, and release (TNR, or TNVR—‘v’ is for vaccinate) programs, and have successfully gotten city ordinances passed that allow for maintaining feral cat colonies. Cook County's 2007 ordinance, for example, permits residents to manage colonies as long as they neuter, spay, and vaccinate the animals against rabies and give them microchip implants.
But the report authors don’t think TNR alone will reduce the impact on birds. “No real-world example of eliminating a colony through TNVR exists, and evidence of large-scale colony reduction is anecdotal,” they write. “Furthermore, TNVR can cost over $100 per cat (including trapping, spaying/neutering, vaccination, and transport), and the cats are still able to prey on native birds and mammals.””
