These are a problem in Costa Rica, where I live. People adopt them when they are puppies, and cute – but abandon them when they grow up and become a nuisance.
I knew a young woman in Orosi who had a vicious dog that attacked other dogs – she thought this was cute. But when she moved away, she left her dog behind – who then attacked people, in revenge.
The U.S. has dog catchers, dog pounds where they can be kept until someone claims them – and if this fails, places where they can be disposed of.
The U.S. has money, but Costa Rica does not. It uses a simpler method – poisoning them. Stray dogs form packs, and these are noted – and then eliminated. This takes time, and the famished dogs can attack people. I have bite marks on my legs myself.
Who poisons the dogs? No one will say. It just happens.